1 ------------------------------------------------------------------------------
2 T H E /proc F I L E S Y S T E M
3 ------------------------------------------------------------------------------
4 /proc/sys Terrehon Bowden <terrehon@pacbell.net> October 7 1999
5 Bodo Bauer <bb@ricochet.net>
7 2.4.x update Jorge Nerin <comandante@zaralinux.com> November 14 2000
8 move /proc/sys Shen Feng <shen@cn.fujitsu.com> April 1 2009
9 ------------------------------------------------------------------------------
10 Version 1.3 Kernel version 2.2.12
11 Kernel version 2.4.0-test11-pre4
12 ------------------------------------------------------------------------------
13 fixes/update part 1.1 Stefani Seibold <stefani@seibold.net> June 9 2009
19 0.1 Introduction/Credits
22 1 Collecting System Information
23 1.1 Process-Specific Subdirectories
25 1.3 IDE devices in /proc/ide
26 1.4 Networking info in /proc/net
28 1.6 Parallel port info in /proc/parport
29 1.7 TTY info in /proc/tty
30 1.8 Miscellaneous kernel statistics in /proc/stat
31 1.9 Ext4 file system parameters
33 2 Modifying System Parameters
35 3 Per-Process Parameters
36 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj - Adjust the oom-killer
38 3.2 /proc/<pid>/oom_score - Display current oom-killer score
39 3.3 /proc/<pid>/io - Display the IO accounting fields
40 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
41 3.5 /proc/<pid>/mountinfo - Information about mounts
42 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
43 3.7 /proc/<pid>/task/<tid>/children - Information about task children
44 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
45 3.9 /proc/<pid>/map_files - Information about memory mapped files
46 3.10 /proc/<pid>/timerslack_ns - Task timerslack value
47 3.11 /proc/<pid>/patch_state - Livepatch patch operation state
52 ------------------------------------------------------------------------------
54 ------------------------------------------------------------------------------
56 0.1 Introduction/Credits
57 ------------------------
59 This documentation is part of a soon (or so we hope) to be released book on
60 the SuSE Linux distribution. As there is no complete documentation for the
61 /proc file system and we've used many freely available sources to write these
62 chapters, it seems only fair to give the work back to the Linux community.
63 This work is based on the 2.2.* kernel version and the upcoming 2.4.*. I'm
64 afraid it's still far from complete, but we hope it will be useful. As far as
65 we know, it is the first 'all-in-one' document about the /proc file system. It
66 is focused on the Intel x86 hardware, so if you are looking for PPC, ARM,
67 SPARC, AXP, etc., features, you probably won't find what you are looking for.
68 It also only covers IPv4 networking, not IPv6 nor other protocols - sorry. But
69 additions and patches are welcome and will be added to this document if you
72 We'd like to thank Alan Cox, Rik van Riel, and Alexey Kuznetsov and a lot of
73 other people for help compiling this documentation. We'd also like to extend a
74 special thank you to Andi Kleen for documentation, which we relied on heavily
75 to create this document, as well as the additional information he provided.
76 Thanks to everybody else who contributed source or docs to the Linux kernel
77 and helped create a great piece of software... :)
79 If you have any comments, corrections or additions, please don't hesitate to
80 contact Bodo Bauer at bb@ricochet.net. We'll be happy to add them to this
83 The latest version of this document is available online at
84 http://tldp.org/LDP/Linux-Filesystem-Hierarchy/html/proc.html
86 If the above direction does not works for you, you could try the kernel
87 mailing list at linux-kernel@vger.kernel.org and/or try to reach me at
88 comandante@zaralinux.com.
93 We don't guarantee the correctness of this document, and if you come to us
94 complaining about how you screwed up your system because of incorrect
95 documentation, we won't feel responsible...
97 ------------------------------------------------------------------------------
98 CHAPTER 1: COLLECTING SYSTEM INFORMATION
99 ------------------------------------------------------------------------------
101 ------------------------------------------------------------------------------
103 ------------------------------------------------------------------------------
104 * Investigating the properties of the pseudo file system /proc and its
105 ability to provide information on the running Linux system
106 * Examining /proc's structure
107 * Uncovering various information about the kernel and the processes running
109 ------------------------------------------------------------------------------
112 The proc file system acts as an interface to internal data structures in the
113 kernel. It can be used to obtain information about the system and to change
114 certain kernel parameters at runtime (sysctl).
116 First, we'll take a look at the read-only parts of /proc. In Chapter 2, we
117 show you how you can use /proc/sys to change settings.
119 1.1 Process-Specific Subdirectories
120 -----------------------------------
122 The directory /proc contains (among other things) one subdirectory for each
123 process running on the system, which is named after the process ID (PID).
125 The link self points to the process reading the file system. Each process
126 subdirectory has the entries listed in Table 1-1.
128 Note that an open a file descriptor to /proc/<pid> or to any of its
129 contained files or subdirectories does not prevent <pid> being reused
130 for some other process in the event that <pid> exits. Operations on
131 open /proc/<pid> file descriptors corresponding to dead processes
132 never act on any new process that the kernel may, through chance, have
133 also assigned the process ID <pid>. Instead, operations on these FDs
134 usually fail with ESRCH.
136 Table 1-1: Process specific entries in /proc
137 ..............................................................................
139 clear_refs Clears page referenced bits shown in smaps output
140 cmdline Command line arguments
141 cpu Current and last cpu in which it was executed (2.4)(smp)
142 cwd Link to the current working directory
143 environ Values of environment variables
144 exe Link to the executable of this process
145 fd Directory, which contains all file descriptors
146 maps Memory maps to executables and library files (2.4)
147 mem Memory held by this process
148 root Link to the root directory of this process
150 statm Process memory status information
151 status Process status in human readable form
152 wchan Present with CONFIG_KALLSYMS=y: it shows the kernel function
153 symbol the task is blocked in - or "0" if not blocked.
155 stack Report full stack trace, enable via CONFIG_STACKTRACE
156 smaps an extension based on maps, showing the memory consumption of
157 each mapping and flags associated with it
158 numa_maps an extension based on maps, showing the memory locality and
159 binding policy as well as mem usage (in pages) of each mapping.
160 ..............................................................................
162 For example, to get the status information of a process, all you have to do is
163 read the file /proc/PID/status:
165 >cat /proc/self/status
195 SigPnd: 0000000000000000
196 ShdPnd: 0000000000000000
197 SigBlk: 0000000000000000
198 SigIgn: 0000000000000000
199 SigCgt: 0000000000000000
200 CapInh: 00000000fffffeff
201 CapPrm: 0000000000000000
202 CapEff: 0000000000000000
203 CapBnd: ffffffffffffffff
204 CapAmb: 0000000000000000
207 Speculation_Store_Bypass: thread vulnerable
208 voluntary_ctxt_switches: 0
209 nonvoluntary_ctxt_switches: 1
211 This shows you nearly the same information you would get if you viewed it with
212 the ps command. In fact, ps uses the proc file system to obtain its
213 information. But you get a more detailed view of the process by reading the
214 file /proc/PID/status. It fields are described in table 1-2.
216 The statm file contains more detailed information about the process
217 memory usage. Its seven fields are explained in Table 1-3. The stat file
218 contains details information about the process itself. Its fields are
219 explained in Table 1-4.
221 (for SMP CONFIG users)
222 For making accounting scalable, RSS related information are handled in an
223 asynchronous manner and the value may not be very precise. To see a precise
224 snapshot of a moment, you can see /proc/<pid>/smaps file and scan page table.
225 It's slow but very precise.
227 Table 1-2: Contents of the status files (as of 4.19)
228 ..............................................................................
230 Name filename of the executable
231 Umask file mode creation mask
232 State state (R is running, S is sleeping, D is sleeping
233 in an uninterruptible wait, Z is zombie,
234 T is traced or stopped)
236 Ngid NUMA group ID (0 if none)
238 PPid process id of the parent process
239 TracerPid PID of process tracing this process (0 if not)
240 Uid Real, effective, saved set, and file system UIDs
241 Gid Real, effective, saved set, and file system GIDs
242 FDSize number of file descriptor slots currently allocated
243 Groups supplementary group list
244 NStgid descendant namespace thread group ID hierarchy
245 NSpid descendant namespace process ID hierarchy
246 NSpgid descendant namespace process group ID hierarchy
247 NSsid descendant namespace session ID hierarchy
248 VmPeak peak virtual memory size
249 VmSize total program size
250 VmLck locked memory size
251 VmPin pinned memory size
252 VmHWM peak resident set size ("high water mark")
253 VmRSS size of memory portions. It contains the three
254 following parts (VmRSS = RssAnon + RssFile + RssShmem)
255 RssAnon size of resident anonymous memory
256 RssFile size of resident file mappings
257 RssShmem size of resident shmem memory (includes SysV shm,
258 mapping of tmpfs and shared anonymous mappings)
259 VmData size of private data segments
260 VmStk size of stack segments
261 VmExe size of text segment
262 VmLib size of shared library code
263 VmPTE size of page table entries
264 VmSwap amount of swap used by anonymous private data
265 (shmem swap usage is not included)
266 HugetlbPages size of hugetlb memory portions
267 CoreDumping process's memory is currently being dumped
268 (killing the process may lead to a corrupted core)
269 THP_enabled process is allowed to use THP (returns 0 when
270 PR_SET_THP_DISABLE is set on the process
271 Threads number of threads
272 SigQ number of signals queued/max. number for queue
273 SigPnd bitmap of pending signals for the thread
274 ShdPnd bitmap of shared pending signals for the process
275 SigBlk bitmap of blocked signals
276 SigIgn bitmap of ignored signals
277 SigCgt bitmap of caught signals
278 CapInh bitmap of inheritable capabilities
279 CapPrm bitmap of permitted capabilities
280 CapEff bitmap of effective capabilities
281 CapBnd bitmap of capabilities bounding set
282 CapAmb bitmap of ambient capabilities
283 NoNewPrivs no_new_privs, like prctl(PR_GET_NO_NEW_PRIV, ...)
284 Seccomp seccomp mode, like prctl(PR_GET_SECCOMP, ...)
285 Speculation_Store_Bypass speculative store bypass mitigation status
286 Cpus_allowed mask of CPUs on which this process may run
287 Cpus_allowed_list Same as previous, but in "list format"
288 Mems_allowed mask of memory nodes allowed to this process
289 Mems_allowed_list Same as previous, but in "list format"
290 voluntary_ctxt_switches number of voluntary context switches
291 nonvoluntary_ctxt_switches number of non voluntary context switches
292 ..............................................................................
294 Table 1-3: Contents of the statm files (as of 2.6.8-rc3)
295 ..............................................................................
297 size total program size (pages) (same as VmSize in status)
298 resident size of memory portions (pages) (same as VmRSS in status)
299 shared number of pages that are shared (i.e. backed by a file, same
300 as RssFile+RssShmem in status)
301 trs number of pages that are 'code' (not including libs; broken,
302 includes data segment)
303 lrs number of pages of library (always 0 on 2.6)
304 drs number of pages of data/stack (including libs; broken,
305 includes library text)
306 dt number of dirty pages (always 0 on 2.6)
307 ..............................................................................
310 Table 1-4: Contents of the stat files (as of 2.6.30-rc7)
311 ..............................................................................
314 tcomm filename of the executable
315 state state (R is running, S is sleeping, D is sleeping in an
316 uninterruptible wait, Z is zombie, T is traced or stopped)
317 ppid process id of the parent process
318 pgrp pgrp of the process
320 tty_nr tty the process uses
321 tty_pgrp pgrp of the tty
323 min_flt number of minor faults
324 cmin_flt number of minor faults with child's
325 maj_flt number of major faults
326 cmaj_flt number of major faults with child's
327 utime user mode jiffies
328 stime kernel mode jiffies
329 cutime user mode jiffies with child's
330 cstime kernel mode jiffies with child's
331 priority priority level
333 num_threads number of threads
334 it_real_value (obsolete, always 0)
335 start_time time the process started after system boot
336 vsize virtual memory size
337 rss resident set memory size
338 rsslim current limit in bytes on the rss
339 start_code address above which program text can run
340 end_code address below which program text can run
341 start_stack address of the start of the main process stack
342 esp current value of ESP
343 eip current value of EIP
344 pending bitmap of pending signals
345 blocked bitmap of blocked signals
346 sigign bitmap of ignored signals
347 sigcatch bitmap of caught signals
348 0 (place holder, used to be the wchan address, use /proc/PID/wchan instead)
351 exit_signal signal to send to parent thread on exit
352 task_cpu which CPU the task is scheduled on
353 rt_priority realtime priority
354 policy scheduling policy (man sched_setscheduler)
355 blkio_ticks time spent waiting for block IO
356 gtime guest time of the task in jiffies
357 cgtime guest time of the task children in jiffies
358 start_data address above which program data+bss is placed
359 end_data address below which program data+bss is placed
360 start_brk address above which program heap can be expanded with brk()
361 arg_start address above which program command line is placed
362 arg_end address below which program command line is placed
363 env_start address above which program environment is placed
364 env_end address below which program environment is placed
365 exit_code the thread's exit_code in the form reported by the waitpid system call
366 ..............................................................................
368 The /proc/PID/maps file containing the currently mapped memory regions and
369 their access permissions.
373 address perms offset dev inode pathname
375 08048000-08049000 r-xp 00000000 03:00 8312 /opt/test
376 08049000-0804a000 rw-p 00001000 03:00 8312 /opt/test
377 0804a000-0806b000 rw-p 00000000 00:00 0 [heap]
378 a7cb1000-a7cb2000 ---p 00000000 00:00 0
379 a7cb2000-a7eb2000 rw-p 00000000 00:00 0
380 a7eb2000-a7eb3000 ---p 00000000 00:00 0
381 a7eb3000-a7ed5000 rw-p 00000000 00:00 0
382 a7ed5000-a8008000 r-xp 00000000 03:00 4222 /lib/libc.so.6
383 a8008000-a800a000 r--p 00133000 03:00 4222 /lib/libc.so.6
384 a800a000-a800b000 rw-p 00135000 03:00 4222 /lib/libc.so.6
385 a800b000-a800e000 rw-p 00000000 00:00 0
386 a800e000-a8022000 r-xp 00000000 03:00 14462 /lib/libpthread.so.0
387 a8022000-a8023000 r--p 00013000 03:00 14462 /lib/libpthread.so.0
388 a8023000-a8024000 rw-p 00014000 03:00 14462 /lib/libpthread.so.0
389 a8024000-a8027000 rw-p 00000000 00:00 0
390 a8027000-a8043000 r-xp 00000000 03:00 8317 /lib/ld-linux.so.2
391 a8043000-a8044000 r--p 0001b000 03:00 8317 /lib/ld-linux.so.2
392 a8044000-a8045000 rw-p 0001c000 03:00 8317 /lib/ld-linux.so.2
393 aff35000-aff4a000 rw-p 00000000 00:00 0 [stack]
394 ffffe000-fffff000 r-xp 00000000 00:00 0 [vdso]
396 where "address" is the address space in the process that it occupies, "perms"
397 is a set of permissions:
403 p = private (copy on write)
405 "offset" is the offset into the mapping, "dev" is the device (major:minor), and
406 "inode" is the inode on that device. 0 indicates that no inode is associated
407 with the memory region, as the case would be with BSS (uninitialized data).
408 The "pathname" shows the name associated file for this mapping. If the mapping
409 is not associated with a file:
411 [heap] = the heap of the program
412 [stack] = the stack of the main process
413 [vdso] = the "virtual dynamic shared object",
414 the kernel system call handler
416 or if empty, the mapping is anonymous.
418 The /proc/PID/smaps is an extension based on maps, showing the memory
419 consumption for each of the process's mappings. For each of mappings there
420 is a series of lines such as the following:
422 08048000-080bc000 r-xp 00000000 03:02 13130 /bin/bash
436 Private_Hugetlb: 0 kB
443 VmFlags: rd ex mr mw me dw
445 the first of these lines shows the same information as is displayed for the
446 mapping in /proc/PID/maps. The remaining lines show the size of the mapping
447 (size), the amount of the mapping that is currently resident in RAM (RSS), the
448 process' proportional share of this mapping (PSS), the number of clean and
449 dirty private pages in the mapping.
451 The "proportional set size" (PSS) of a process is the count of pages it has
452 in memory, where each page is divided by the number of processes sharing it.
453 So if a process has 1000 pages all to itself, and 1000 shared with one other
454 process, its PSS will be 1500.
455 Note that even a page which is part of a MAP_SHARED mapping, but has only
456 a single pte mapped, i.e. is currently used by only one process, is accounted
457 as private and not as shared.
458 "Referenced" indicates the amount of memory currently marked as referenced or
460 "Anonymous" shows the amount of memory that does not belong to any file. Even
461 a mapping associated with a file may contain anonymous pages: when MAP_PRIVATE
462 and a page is modified, the file page is replaced by a private anonymous copy.
463 "LazyFree" shows the amount of memory which is marked by madvise(MADV_FREE).
464 The memory isn't freed immediately with madvise(). It's freed in memory
465 pressure if the memory is clean. Please note that the printed value might
466 be lower than the real value due to optimizations used in the current
467 implementation. If this is not desirable please file a bug report.
468 "AnonHugePages" shows the ammount of memory backed by transparent hugepage.
469 "ShmemPmdMapped" shows the ammount of shared (shmem/tmpfs) memory backed by
471 "Shared_Hugetlb" and "Private_Hugetlb" show the ammounts of memory backed by
472 hugetlbfs page which is *not* counted in "RSS" or "PSS" field for historical
473 reasons. And these are not included in {Shared,Private}_{Clean,Dirty} field.
474 "Swap" shows how much would-be-anonymous memory is also used, but out on swap.
475 For shmem mappings, "Swap" includes also the size of the mapped (and not
476 replaced by copy-on-write) part of the underlying shmem object out on swap.
477 "SwapPss" shows proportional swap share of this mapping. Unlike "Swap", this
478 does not take into account swapped out page of underlying shmem objects.
479 "Locked" indicates whether the mapping is locked in memory or not.
480 "THPeligible" indicates whether the mapping is eligible for THP pages - 1 if
483 "VmFlags" field deserves a separate description. This member represents the kernel
484 flags associated with the particular virtual memory area in two letter encoded
485 manner. The codes are the following:
494 gd - stack segment growns down
496 dw - disabled write to the mapped file
497 lo - pages are locked in memory
498 io - memory mapped I/O area
499 sr - sequential read advise provided
500 rr - random read advise provided
501 dc - do not copy area on fork
502 de - do not expand area on remapping
503 ac - area is accountable
504 nr - swap space is not reserved for the area
505 ht - area uses huge tlb pages
506 ar - architecture specific flag
507 dd - do not include area into core dump
510 hg - huge page advise flag
511 nh - no-huge page advise flag
512 mg - mergable advise flag
514 Note that there is no guarantee that every flag and associated mnemonic will
515 be present in all further kernel releases. Things get changed, the flags may
516 be vanished or the reverse -- new added. Interpretation of their meaning
517 might change in future as well. So each consumer of these flags has to
518 follow each specific kernel version for the exact semantic.
520 This file is only present if the CONFIG_MMU kernel configuration option is
523 Note: reading /proc/PID/maps or /proc/PID/smaps is inherently racy (consistent
524 output can be achieved only in the single read call).
525 This typically manifests when doing partial reads of these files while the
526 memory map is being modified. Despite the races, we do provide the following
529 1) The mapped addresses never go backwards, which implies no two
530 regions will ever overlap.
531 2) If there is something at a given vaddr during the entirety of the
532 life of the smaps/maps walk, there will be some output for it.
535 The /proc/PID/clear_refs is used to reset the PG_Referenced and ACCESSED/YOUNG
536 bits on both physical and virtual pages associated with a process, and the
537 soft-dirty bit on pte (see Documentation/admin-guide/mm/soft-dirty.rst
539 To clear the bits for all the pages associated with the process
540 > echo 1 > /proc/PID/clear_refs
542 To clear the bits for the anonymous pages associated with the process
543 > echo 2 > /proc/PID/clear_refs
545 To clear the bits for the file mapped pages associated with the process
546 > echo 3 > /proc/PID/clear_refs
548 To clear the soft-dirty bit
549 > echo 4 > /proc/PID/clear_refs
551 To reset the peak resident set size ("high water mark") to the process's
553 > echo 5 > /proc/PID/clear_refs
555 Any other value written to /proc/PID/clear_refs will have no effect.
557 The /proc/pid/pagemap gives the PFN, which can be used to find the pageflags
558 using /proc/kpageflags and number of times a page is mapped using
559 /proc/kpagecount. For detailed explanation, see
560 Documentation/admin-guide/mm/pagemap.rst.
562 The /proc/pid/numa_maps is an extension based on maps, showing the memory
563 locality and binding policy, as well as the memory usage (in pages) of
564 each mapping. The output follows a general format where mapping details get
565 summarized separated by blank spaces, one mapping per each file line:
567 address policy mapping details
569 00400000 default file=/usr/local/bin/app mapped=1 active=0 N3=1 kernelpagesize_kB=4
570 00600000 default file=/usr/local/bin/app anon=1 dirty=1 N3=1 kernelpagesize_kB=4
571 3206000000 default file=/lib64/ld-2.12.so mapped=26 mapmax=6 N0=24 N3=2 kernelpagesize_kB=4
572 320621f000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
573 3206220000 default file=/lib64/ld-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
574 3206221000 default anon=1 dirty=1 N3=1 kernelpagesize_kB=4
575 3206800000 default file=/lib64/libc-2.12.so mapped=59 mapmax=21 active=55 N0=41 N3=18 kernelpagesize_kB=4
576 320698b000 default file=/lib64/libc-2.12.so
577 3206b8a000 default file=/lib64/libc-2.12.so anon=2 dirty=2 N3=2 kernelpagesize_kB=4
578 3206b8e000 default file=/lib64/libc-2.12.so anon=1 dirty=1 N3=1 kernelpagesize_kB=4
579 3206b8f000 default anon=3 dirty=3 active=1 N3=3 kernelpagesize_kB=4
580 7f4dc10a2000 default anon=3 dirty=3 N3=3 kernelpagesize_kB=4
581 7f4dc10b4000 default anon=2 dirty=2 active=1 N3=2 kernelpagesize_kB=4
582 7f4dc1200000 default file=/anon_hugepage\040(deleted) huge anon=1 dirty=1 N3=1 kernelpagesize_kB=2048
583 7fff335f0000 default stack anon=3 dirty=3 N3=3 kernelpagesize_kB=4
584 7fff3369d000 default mapped=1 mapmax=35 active=0 N3=1 kernelpagesize_kB=4
587 "address" is the starting address for the mapping;
588 "policy" reports the NUMA memory policy set for the mapping (see Documentation/admin-guide/mm/numa_memory_policy.rst);
589 "mapping details" summarizes mapping data such as mapping type, page usage counters,
590 node locality page counters (N0 == node0, N1 == node1, ...) and the kernel page
591 size, in KB, that is backing the mapping up.
596 Similar to the process entries, the kernel data files give information about
597 the running kernel. The files used to obtain this information are contained in
598 /proc and are listed in Table 1-5. Not all of these will be present in your
599 system. It depends on the kernel configuration and the loaded modules, which
600 files are there, and which are missing.
602 Table 1-5: Kernel info in /proc
603 ..............................................................................
605 apm Advanced power management info
606 buddyinfo Kernel memory allocator information (see text) (2.5)
607 bus Directory containing bus specific information
608 cmdline Kernel command line
609 cpuinfo Info about the CPU
610 devices Available devices (block and character)
611 dma Used DMS channels
612 filesystems Supported filesystems
613 driver Various drivers grouped here, currently rtc (2.4)
614 execdomains Execdomains, related to security (2.4)
615 fb Frame Buffer devices (2.4)
616 fs File system parameters, currently nfs/exports (2.4)
617 ide Directory containing info about the IDE subsystem
618 interrupts Interrupt usage
619 iomem Memory map (2.4)
620 ioports I/O port usage
621 irq Masks for irq to cpu affinity (2.4)(smp?)
622 isapnp ISA PnP (Plug&Play) Info (2.4)
623 kcore Kernel core image (can be ELF or A.OUT(deprecated in 2.4))
625 ksyms Kernel symbol table
626 loadavg Load average of last 1, 5 & 15 minutes
630 modules List of loaded modules
631 mounts Mounted filesystems
632 net Networking info (see text)
633 pagetypeinfo Additional page allocator information (see text) (2.5)
634 partitions Table of partitions known to the system
635 pci Deprecated info of PCI bus (new way -> /proc/bus/pci/,
636 decoupled by lspci (2.4)
638 scsi SCSI info (see text)
639 slabinfo Slab pool info
640 softirqs softirq usage
641 stat Overall statistics
642 swaps Swap space utilization
644 sysvipc Info of SysVIPC Resources (msg, sem, shm) (2.4)
645 tty Info of tty drivers
646 uptime Wall clock since boot, combined idle time of all cpus
647 version Kernel version
648 video bttv info of video resources (2.4)
649 vmallocinfo Show vmalloced areas
650 ..............................................................................
652 You can, for example, check which interrupts are currently in use and what
653 they are used for by looking in the file /proc/interrupts:
655 > cat /proc/interrupts
657 0: 8728810 XT-PIC timer
658 1: 895 XT-PIC keyboard
660 3: 531695 XT-PIC aha152x
661 4: 2014133 XT-PIC serial
662 5: 44401 XT-PIC pcnet_cs
665 12: 182918 XT-PIC PS/2 Mouse
667 14: 1232265 XT-PIC ide0
671 In 2.4.* a couple of lines where added to this file LOC & ERR (this time is the
672 output of a SMP machine):
674 > cat /proc/interrupts
677 0: 1243498 1214548 IO-APIC-edge timer
678 1: 8949 8958 IO-APIC-edge keyboard
679 2: 0 0 XT-PIC cascade
680 5: 11286 10161 IO-APIC-edge soundblaster
681 8: 1 0 IO-APIC-edge rtc
682 9: 27422 27407 IO-APIC-edge 3c503
683 12: 113645 113873 IO-APIC-edge PS/2 Mouse
685 14: 22491 24012 IO-APIC-edge ide0
686 15: 2183 2415 IO-APIC-edge ide1
687 17: 30564 30414 IO-APIC-level eth0
688 18: 177 164 IO-APIC-level bttv
693 NMI is incremented in this case because every timer interrupt generates a NMI
694 (Non Maskable Interrupt) which is used by the NMI Watchdog to detect lockups.
696 LOC is the local interrupt counter of the internal APIC of every CPU.
698 ERR is incremented in the case of errors in the IO-APIC bus (the bus that
699 connects the CPUs in a SMP system. This means that an error has been detected,
700 the IO-APIC automatically retry the transmission, so it should not be a big
701 problem, but you should read the SMP-FAQ.
703 In 2.6.2* /proc/interrupts was expanded again. This time the goal was for
704 /proc/interrupts to display every IRQ vector in use by the system, not
705 just those considered 'most important'. The new vectors are:
707 THR -- interrupt raised when a machine check threshold counter
708 (typically counting ECC corrected errors of memory or cache) exceeds
709 a configurable threshold. Only available on some systems.
711 TRM -- a thermal event interrupt occurs when a temperature threshold
712 has been exceeded for the CPU. This interrupt may also be generated
713 when the temperature drops back to normal.
715 SPU -- a spurious interrupt is some interrupt that was raised then lowered
716 by some IO device before it could be fully processed by the APIC. Hence
717 the APIC sees the interrupt but does not know what device it came from.
718 For this case the APIC will generate the interrupt with a IRQ vector
719 of 0xff. This might also be generated by chipset bugs.
721 RES, CAL, TLB -- rescheduling, call and TLB flush interrupts are
722 sent from one CPU to another per the needs of the OS. Typically,
723 their statistics are used by kernel developers and interested users to
724 determine the occurrence of interrupts of the given type.
726 The above IRQ vectors are displayed only when relevant. For example,
727 the threshold vector does not exist on x86_64 platforms. Others are
728 suppressed when the system is a uniprocessor. As of this writing, only
729 i386 and x86_64 platforms support the new IRQ vector displays.
731 Of some interest is the introduction of the /proc/irq directory to 2.4.
732 It could be used to set IRQ to CPU affinity, this means that you can "hook" an
733 IRQ to only one CPU, or to exclude a CPU of handling IRQs. The contents of the
734 irq subdir is one subdir for each IRQ, and two files; default_smp_affinity and
739 0 10 12 14 16 18 2 4 6 8 prof_cpu_mask
740 1 11 13 15 17 19 3 5 7 9 default_smp_affinity
744 smp_affinity is a bitmask, in which you can specify which CPUs can handle the
745 IRQ, you can set it by doing:
747 > echo 1 > /proc/irq/10/smp_affinity
749 This means that only the first CPU will handle the IRQ, but you can also echo
750 5 which means that only the first and third CPU can handle the IRQ.
752 The contents of each smp_affinity file is the same by default:
754 > cat /proc/irq/0/smp_affinity
757 There is an alternate interface, smp_affinity_list which allows specifying
758 a cpu range instead of a bitmask:
760 > cat /proc/irq/0/smp_affinity_list
763 The default_smp_affinity mask applies to all non-active IRQs, which are the
764 IRQs which have not yet been allocated/activated, and hence which lack a
765 /proc/irq/[0-9]* directory.
767 The node file on an SMP system shows the node to which the device using the IRQ
768 reports itself as being attached. This hardware locality information does not
769 include information about any possible driver locality preference.
771 prof_cpu_mask specifies which CPUs are to be profiled by the system wide
772 profiler. Default value is ffffffff (all cpus if there are only 32 of them).
774 The way IRQs are routed is handled by the IO-APIC, and it's Round Robin
775 between all the CPUs which are allowed to handle it. As usual the kernel has
776 more info than you and does a better job than you, so the defaults are the
777 best choice for almost everyone. [Note this applies only to those IO-APIC's
778 that support "Round Robin" interrupt distribution.]
780 There are three more important subdirectories in /proc: net, scsi, and sys.
781 The general rule is that the contents, or even the existence of these
782 directories, depend on your kernel configuration. If SCSI is not enabled, the
783 directory scsi may not exist. The same is true with the net, which is there
784 only when networking support is present in the running kernel.
786 The slabinfo file gives information about memory usage at the slab level.
787 Linux uses slab pools for memory management above page level in version 2.2.
788 Commonly used objects have their own slab pool (such as network buffers,
789 directory cache, and so on).
791 ..............................................................................
793 > cat /proc/buddyinfo
795 Node 0, zone DMA 0 4 5 4 4 3 ...
796 Node 0, zone Normal 1 0 0 1 101 8 ...
797 Node 0, zone HighMem 2 0 0 1 1 0 ...
799 External fragmentation is a problem under some workloads, and buddyinfo is a
800 useful tool for helping diagnose these problems. Buddyinfo will give you a
801 clue as to how big an area you can safely allocate, or why a previous
804 Each column represents the number of pages of a certain order which are
805 available. In this case, there are 0 chunks of 2^0*PAGE_SIZE available in
806 ZONE_DMA, 4 chunks of 2^1*PAGE_SIZE in ZONE_DMA, 101 chunks of 2^4*PAGE_SIZE
807 available in ZONE_NORMAL, etc...
809 More information relevant to external fragmentation can be found in
812 > cat /proc/pagetypeinfo
816 Free pages count per migrate type at order 0 1 2 3 4 5 6 7 8 9 10
817 Node 0, zone DMA, type Unmovable 0 0 0 1 1 1 1 1 1 1 0
818 Node 0, zone DMA, type Reclaimable 0 0 0 0 0 0 0 0 0 0 0
819 Node 0, zone DMA, type Movable 1 1 2 1 2 1 1 0 1 0 2
820 Node 0, zone DMA, type Reserve 0 0 0 0 0 0 0 0 0 1 0
821 Node 0, zone DMA, type Isolate 0 0 0 0 0 0 0 0 0 0 0
822 Node 0, zone DMA32, type Unmovable 103 54 77 1 1 1 11 8 7 1 9
823 Node 0, zone DMA32, type Reclaimable 0 0 2 1 0 0 0 0 1 0 0
824 Node 0, zone DMA32, type Movable 169 152 113 91 77 54 39 13 6 1 452
825 Node 0, zone DMA32, type Reserve 1 2 2 2 2 0 1 1 1 1 0
826 Node 0, zone DMA32, type Isolate 0 0 0 0 0 0 0 0 0 0 0
828 Number of blocks type Unmovable Reclaimable Movable Reserve Isolate
829 Node 0, zone DMA 2 0 5 1 0
830 Node 0, zone DMA32 41 6 967 2 0
832 Fragmentation avoidance in the kernel works by grouping pages of different
833 migrate types into the same contiguous regions of memory called page blocks.
834 A page block is typically the size of the default hugepage size e.g. 2MB on
835 X86-64. By keeping pages grouped based on their ability to move, the kernel
836 can reclaim pages within a page block to satisfy a high-order allocation.
838 The pagetypinfo begins with information on the size of a page block. It
839 then gives the same type of information as buddyinfo except broken down
840 by migrate-type and finishes with details on how many page blocks of each
843 If min_free_kbytes has been tuned correctly (recommendations made by hugeadm
844 from libhugetlbfs https://github.com/libhugetlbfs/libhugetlbfs/), one can
845 make an estimate of the likely number of huge pages that can be allocated
846 at a given point in time. All the "Movable" blocks should be allocatable
847 unless memory has been mlock()'d. Some of the Reclaimable blocks should
848 also be allocatable although a lot of filesystem metadata may have to be
849 reclaimed to achieve this.
851 ..............................................................................
855 Provides information about distribution and utilization of memory. This
856 varies by architecture and compile options. The following is from a
857 16GB PIII, which has highmem enabled. You may not have all of these fields.
861 MemTotal: 16344972 kB
863 MemAvailable: 14836172 kB
869 HighTotal: 15597528 kB
870 HighFree: 13629632 kB
880 KReclaimable: 168048 kB
882 SReclaimable: 159856 kB
883 SUnreclaim: 124508 kB
888 CommitLimit: 7669796 kB
889 Committed_AS: 100056 kB
890 VmallocTotal: 112216 kB
892 VmallocChunk: 111088 kB
894 HardwareCorrupted: 0 kB
895 AnonHugePages: 49152 kB
900 MemTotal: Total usable ram (i.e. physical ram minus a few reserved
901 bits and the kernel binary code)
902 MemFree: The sum of LowFree+HighFree
903 MemAvailable: An estimate of how much memory is available for starting new
904 applications, without swapping. Calculated from MemFree,
905 SReclaimable, the size of the file LRU lists, and the low
906 watermarks in each zone.
907 The estimate takes into account that the system needs some
908 page cache to function well, and that not all reclaimable
909 slab will be reclaimable, due to items being in use. The
910 impact of those factors will vary from system to system.
911 Buffers: Relatively temporary storage for raw disk blocks
912 shouldn't get tremendously large (20MB or so)
913 Cached: in-memory cache for files read from the disk (the
914 pagecache). Doesn't include SwapCached
915 SwapCached: Memory that once was swapped out, is swapped back in but
916 still also is in the swapfile (if memory is needed it
917 doesn't need to be swapped out AGAIN because it is already
918 in the swapfile. This saves I/O)
919 Active: Memory that has been used more recently and usually not
920 reclaimed unless absolutely necessary.
921 Inactive: Memory which has been less recently used. It is more
922 eligible to be reclaimed for other purposes
924 HighFree: Highmem is all memory above ~860MB of physical memory
925 Highmem areas are for use by userspace programs, or
926 for the pagecache. The kernel must use tricks to access
927 this memory, making it slower to access than lowmem.
929 LowFree: Lowmem is memory which can be used for everything that
930 highmem can be used for, but it is also available for the
931 kernel's use for its own data structures. Among many
932 other things, it is where everything from the Slab is
933 allocated. Bad things happen when you're out of lowmem.
934 SwapTotal: total amount of swap space available
935 SwapFree: Memory which has been evicted from RAM, and is temporarily
937 Dirty: Memory which is waiting to get written back to the disk
938 Writeback: Memory which is actively being written back to the disk
939 AnonPages: Non-file backed pages mapped into userspace page tables
940 HardwareCorrupted: The amount of RAM/memory in KB, the kernel identifies as
942 AnonHugePages: Non-file backed huge pages mapped into userspace page tables
943 Mapped: files which have been mmaped, such as libraries
944 Shmem: Total memory used by shared memory (shmem) and tmpfs
945 ShmemHugePages: Memory used by shared memory (shmem) and tmpfs allocated
947 ShmemPmdMapped: Shared memory mapped into userspace with huge pages
948 KReclaimable: Kernel allocations that the kernel will attempt to reclaim
949 under memory pressure. Includes SReclaimable (below), and other
950 direct allocations with a shrinker.
951 Slab: in-kernel data structures cache
952 SReclaimable: Part of Slab, that might be reclaimed, such as caches
953 SUnreclaim: Part of Slab, that cannot be reclaimed on memory pressure
954 PageTables: amount of memory dedicated to the lowest level of page
956 NFS_Unstable: NFS pages sent to the server, but not yet committed to stable
958 Bounce: Memory used for block device "bounce buffers"
959 WritebackTmp: Memory used by FUSE for temporary writeback buffers
960 CommitLimit: Based on the overcommit ratio ('vm.overcommit_ratio'),
961 this is the total amount of memory currently available to
962 be allocated on the system. This limit is only adhered to
963 if strict overcommit accounting is enabled (mode 2 in
964 'vm.overcommit_memory').
965 The CommitLimit is calculated with the following formula:
966 CommitLimit = ([total RAM pages] - [total huge TLB pages]) *
967 overcommit_ratio / 100 + [total swap pages]
968 For example, on a system with 1G of physical RAM and 7G
969 of swap with a `vm.overcommit_ratio` of 30 it would
970 yield a CommitLimit of 7.3G.
971 For more details, see the memory overcommit documentation
972 in vm/overcommit-accounting.
973 Committed_AS: The amount of memory presently allocated on the system.
974 The committed memory is a sum of all of the memory which
975 has been allocated by processes, even if it has not been
976 "used" by them as of yet. A process which malloc()'s 1G
977 of memory, but only touches 300M of it will show up as
978 using 1G. This 1G is memory which has been "committed" to
979 by the VM and can be used at any time by the allocating
980 application. With strict overcommit enabled on the system
981 (mode 2 in 'vm.overcommit_memory'),allocations which would
982 exceed the CommitLimit (detailed above) will not be permitted.
983 This is useful if one needs to guarantee that processes will
984 not fail due to lack of memory once that memory has been
985 successfully allocated.
986 VmallocTotal: total size of vmalloc memory area
987 VmallocUsed: amount of vmalloc area which is used
988 VmallocChunk: largest contiguous block of vmalloc area which is free
989 Percpu: Memory allocated to the percpu allocator used to back percpu
990 allocations. This stat excludes the cost of metadata.
992 ..............................................................................
996 Provides information about vmalloced/vmaped areas. One line per area,
997 containing the virtual address range of the area, size in bytes,
998 caller information of the creator, and optional information depending
999 on the kind of area :
1001 pages=nr number of pages
1002 phys=addr if a physical address was specified
1003 ioremap I/O mapping (ioremap() and friends)
1004 vmalloc vmalloc() area
1006 user VM_USERMAP area
1007 vpages buffer for pages pointers was vmalloced (huge area)
1008 N<node>=nr (Only on NUMA kernels)
1009 Number of pages allocated on memory node <node>
1011 > cat /proc/vmallocinfo
1012 0xffffc20000000000-0xffffc20000201000 2101248 alloc_large_system_hash+0x204 ...
1013 /0x2c0 pages=512 vmalloc N0=128 N1=128 N2=128 N3=128
1014 0xffffc20000201000-0xffffc20000302000 1052672 alloc_large_system_hash+0x204 ...
1015 /0x2c0 pages=256 vmalloc N0=64 N1=64 N2=64 N3=64
1016 0xffffc20000302000-0xffffc20000304000 8192 acpi_tb_verify_table+0x21/0x4f...
1017 phys=7fee8000 ioremap
1018 0xffffc20000304000-0xffffc20000307000 12288 acpi_tb_verify_table+0x21/0x4f...
1019 phys=7fee7000 ioremap
1020 0xffffc2000031d000-0xffffc2000031f000 8192 init_vdso_vars+0x112/0x210
1021 0xffffc2000031f000-0xffffc2000032b000 49152 cramfs_uncompress_init+0x2e ...
1022 /0x80 pages=11 vmalloc N0=3 N1=3 N2=2 N3=3
1023 0xffffc2000033a000-0xffffc2000033d000 12288 sys_swapon+0x640/0xac0 ...
1024 pages=2 vmalloc N1=2
1025 0xffffc20000347000-0xffffc2000034c000 20480 xt_alloc_table_info+0xfe ...
1026 /0x130 [x_tables] pages=4 vmalloc N0=4
1027 0xffffffffa0000000-0xffffffffa000f000 61440 sys_init_module+0xc27/0x1d00 ...
1028 pages=14 vmalloc N2=14
1029 0xffffffffa000f000-0xffffffffa0014000 20480 sys_init_module+0xc27/0x1d00 ...
1030 pages=4 vmalloc N1=4
1031 0xffffffffa0014000-0xffffffffa0017000 12288 sys_init_module+0xc27/0x1d00 ...
1032 pages=2 vmalloc N1=2
1033 0xffffffffa0017000-0xffffffffa0022000 45056 sys_init_module+0xc27/0x1d00 ...
1034 pages=10 vmalloc N0=10
1036 ..............................................................................
1040 Provides counts of softirq handlers serviced since boot time, for each cpu.
1042 > cat /proc/softirqs
1045 TIMER: 27166 27120 27097 27034
1050 SCHED: 27035 26983 26971 26746
1052 RCU: 1678 1769 2178 2250
1055 1.3 IDE devices in /proc/ide
1056 ----------------------------
1058 The subdirectory /proc/ide contains information about all IDE devices of which
1059 the kernel is aware. There is one subdirectory for each IDE controller, the
1060 file drivers and a link for each IDE device, pointing to the device directory
1061 in the controller specific subtree.
1063 The file drivers contains general information about the drivers used for the
1066 > cat /proc/ide/drivers
1067 ide-cdrom version 4.53
1068 ide-disk version 1.08
1070 More detailed information can be found in the controller specific
1071 subdirectories. These are named ide0, ide1 and so on. Each of these
1072 directories contains the files shown in table 1-6.
1075 Table 1-6: IDE controller info in /proc/ide/ide?
1076 ..............................................................................
1078 channel IDE channel (0 or 1)
1079 config Configuration (only for PCI/IDE bridge)
1081 model Type/Chipset of IDE controller
1082 ..............................................................................
1084 Each device connected to a controller has a separate subdirectory in the
1085 controllers directory. The files listed in table 1-7 are contained in these
1089 Table 1-7: IDE device information
1090 ..............................................................................
1093 capacity Capacity of the medium (in 512Byte blocks)
1094 driver driver and version
1095 geometry physical and logical geometry
1096 identify device identify block
1098 model device identifier
1099 settings device setup
1100 smart_thresholds IDE disk management thresholds
1101 smart_values IDE disk management values
1102 ..............................................................................
1104 The most interesting file is settings. This file contains a nice overview of
1105 the drive parameters:
1107 # cat /proc/ide/ide0/hda/settings
1108 name value min max mode
1109 ---- ----- --- --- ----
1110 bios_cyl 526 0 65535 rw
1111 bios_head 255 0 255 rw
1112 bios_sect 63 0 63 rw
1113 breada_readahead 4 0 127 rw
1115 file_readahead 72 0 2097151 rw
1117 keepsettings 0 0 1 rw
1118 max_kb_per_request 122 1 127 rw
1122 pio_mode write-only 0 255 w
1128 1.4 Networking info in /proc/net
1129 --------------------------------
1131 The subdirectory /proc/net follows the usual pattern. Table 1-8 shows the
1132 additional values you get for IP version 6 if you configure the kernel to
1133 support this. Table 1-9 lists the files and their meaning.
1136 Table 1-8: IPv6 info in /proc/net
1137 ..............................................................................
1139 udp6 UDP sockets (IPv6)
1140 tcp6 TCP sockets (IPv6)
1141 raw6 Raw device statistics (IPv6)
1142 igmp6 IP multicast addresses, which this host joined (IPv6)
1143 if_inet6 List of IPv6 interface addresses
1144 ipv6_route Kernel routing table for IPv6
1145 rt6_stats Global IPv6 routing tables statistics
1146 sockstat6 Socket statistics (IPv6)
1147 snmp6 Snmp data (IPv6)
1148 ..............................................................................
1151 Table 1-9: Network info in /proc/net
1152 ..............................................................................
1154 arp Kernel ARP table
1155 dev network devices with statistics
1156 dev_mcast the Layer2 multicast groups a device is listening too
1157 (interface index, label, number of references, number of bound
1159 dev_stat network device status
1160 ip_fwchains Firewall chain linkage
1161 ip_fwnames Firewall chain names
1162 ip_masq Directory containing the masquerading tables
1163 ip_masquerade Major masquerading table
1164 netstat Network statistics
1165 raw raw device statistics
1166 route Kernel routing table
1167 rpc Directory containing rpc info
1168 rt_cache Routing cache
1170 sockstat Socket statistics
1173 unix UNIX domain sockets
1174 wireless Wireless interface data (Wavelan etc)
1175 igmp IP multicast addresses, which this host joined
1176 psched Global packet scheduler parameters.
1177 netlink List of PF_NETLINK sockets
1178 ip_mr_vifs List of multicast virtual interfaces
1179 ip_mr_cache List of multicast routing cache
1180 ..............................................................................
1182 You can use this information to see which network devices are available in
1183 your system and how much traffic was routed over those devices:
1186 Inter-|Receive |[...
1187 face |bytes packets errs drop fifo frame compressed multicast|[...
1188 lo: 908188 5596 0 0 0 0 0 0 [...
1189 ppp0:15475140 20721 410 0 0 410 0 0 [...
1190 eth0: 614530 7085 0 0 0 0 0 1 [...
1193 ...] bytes packets errs drop fifo colls carrier compressed
1194 ...] 908188 5596 0 0 0 0 0 0
1195 ...] 1375103 17405 0 0 0 0 0 0
1196 ...] 1703981 5535 0 0 0 3 0 0
1198 In addition, each Channel Bond interface has its own directory. For
1199 example, the bond0 device will have a directory called /proc/net/bond0/.
1200 It will contain information that is specific to that bond, such as the
1201 current slaves of the bond, the link status of the slaves, and how
1202 many times the slaves link has failed.
1207 If you have a SCSI host adapter in your system, you'll find a subdirectory
1208 named after the driver for this adapter in /proc/scsi. You'll also see a list
1209 of all recognized SCSI devices in /proc/scsi:
1211 >cat /proc/scsi/scsi
1213 Host: scsi0 Channel: 00 Id: 00 Lun: 00
1214 Vendor: IBM Model: DGHS09U Rev: 03E0
1215 Type: Direct-Access ANSI SCSI revision: 03
1216 Host: scsi0 Channel: 00 Id: 06 Lun: 00
1217 Vendor: PIONEER Model: CD-ROM DR-U06S Rev: 1.04
1218 Type: CD-ROM ANSI SCSI revision: 02
1221 The directory named after the driver has one file for each adapter found in
1222 the system. These files contain information about the controller, including
1223 the used IRQ and the IO address range. The amount of information shown is
1224 dependent on the adapter you use. The example shows the output for an Adaptec
1225 AHA-2940 SCSI adapter:
1227 > cat /proc/scsi/aic7xxx/0
1229 Adaptec AIC7xxx driver version: 5.1.19/3.2.4
1231 TCQ Enabled By Default : Disabled
1232 AIC7XXX_PROC_STATS : Disabled
1233 AIC7XXX_RESET_DELAY : 5
1234 Adapter Configuration:
1235 SCSI Adapter: Adaptec AHA-294X Ultra SCSI host adapter
1236 Ultra Wide Controller
1237 PCI MMAPed I/O Base: 0xeb001000
1238 Adapter SEEPROM Config: SEEPROM found and used.
1239 Adaptec SCSI BIOS: Enabled
1241 SCBs: Active 0, Max Active 2,
1242 Allocated 15, HW 16, Page 255
1244 BIOS Control Word: 0x18b6
1245 Adapter Control Word: 0x005b
1246 Extended Translation: Enabled
1247 Disconnect Enable Flags: 0xffff
1248 Ultra Enable Flags: 0x0001
1249 Tag Queue Enable Flags: 0x0000
1250 Ordered Queue Tag Flags: 0x0000
1251 Default Tag Queue Depth: 8
1252 Tagged Queue By Device array for aic7xxx host instance 0:
1253 {255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255}
1254 Actual queue depth per device for aic7xxx host instance 0:
1255 {1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1}
1258 Device using Wide/Sync transfers at 40.0 MByte/sec, offset 8
1259 Transinfo settings: current(12/8/1/0), goal(12/8/1/0), user(12/15/1/0)
1260 Total transfers 160151 (74577 reads and 85574 writes)
1262 Device using Narrow/Sync transfers at 5.0 MByte/sec, offset 15
1263 Transinfo settings: current(50/15/0/0), goal(50/15/0/0), user(50/15/0/0)
1264 Total transfers 0 (0 reads and 0 writes)
1267 1.6 Parallel port info in /proc/parport
1268 ---------------------------------------
1270 The directory /proc/parport contains information about the parallel ports of
1271 your system. It has one subdirectory for each port, named after the port
1274 These directories contain the four files shown in Table 1-10.
1277 Table 1-10: Files in /proc/parport
1278 ..............................................................................
1280 autoprobe Any IEEE-1284 device ID information that has been acquired.
1281 devices list of the device drivers using that port. A + will appear by the
1282 name of the device currently using the port (it might not appear
1284 hardware Parallel port's base address, IRQ line and DMA channel.
1285 irq IRQ that parport is using for that port. This is in a separate
1286 file to allow you to alter it by writing a new value in (IRQ
1288 ..............................................................................
1290 1.7 TTY info in /proc/tty
1291 -------------------------
1293 Information about the available and actually used tty's can be found in the
1294 directory /proc/tty.You'll find entries for drivers and line disciplines in
1295 this directory, as shown in Table 1-11.
1298 Table 1-11: Files in /proc/tty
1299 ..............................................................................
1301 drivers list of drivers and their usage
1302 ldiscs registered line disciplines
1303 driver/serial usage statistic and status of single tty lines
1304 ..............................................................................
1306 To see which tty's are currently in use, you can simply look into the file
1309 > cat /proc/tty/drivers
1310 pty_slave /dev/pts 136 0-255 pty:slave
1311 pty_master /dev/ptm 128 0-255 pty:master
1312 pty_slave /dev/ttyp 3 0-255 pty:slave
1313 pty_master /dev/pty 2 0-255 pty:master
1314 serial /dev/cua 5 64-67 serial:callout
1315 serial /dev/ttyS 4 64-67 serial
1316 /dev/tty0 /dev/tty0 4 0 system:vtmaster
1317 /dev/ptmx /dev/ptmx 5 2 system
1318 /dev/console /dev/console 5 1 system:console
1319 /dev/tty /dev/tty 5 0 system:/dev/tty
1320 unknown /dev/tty 4 1-63 console
1323 1.8 Miscellaneous kernel statistics in /proc/stat
1324 -------------------------------------------------
1326 Various pieces of information about kernel activity are available in the
1327 /proc/stat file. All of the numbers reported in this file are aggregates
1328 since the system first booted. For a quick look, simply cat the file:
1331 cpu 2255 34 2290 22625563 6290 127 456 0 0 0
1332 cpu0 1132 34 1441 11311718 3675 127 438 0 0 0
1333 cpu1 1123 0 849 11313845 2614 0 18 0 0 0
1334 intr 114930548 113199788 3 0 5 263 0 4 [... lots more numbers ...]
1340 softirq 183433 0 21755 12 39 1137 231 21459 2263
1342 The very first "cpu" line aggregates the numbers in all of the other "cpuN"
1343 lines. These numbers identify the amount of time the CPU has spent performing
1344 different kinds of work. Time units are in USER_HZ (typically hundredths of a
1345 second). The meanings of the columns are as follows, from left to right:
1347 - user: normal processes executing in user mode
1348 - nice: niced processes executing in user mode
1349 - system: processes executing in kernel mode
1350 - idle: twiddling thumbs
1351 - iowait: In a word, iowait stands for waiting for I/O to complete. But there
1352 are several problems:
1353 1. Cpu will not wait for I/O to complete, iowait is the time that a task is
1354 waiting for I/O to complete. When cpu goes into idle state for
1355 outstanding task io, another task will be scheduled on this CPU.
1356 2. In a multi-core CPU, the task waiting for I/O to complete is not running
1357 on any CPU, so the iowait of each CPU is difficult to calculate.
1358 3. The value of iowait field in /proc/stat will decrease in certain
1360 So, the iowait is not reliable by reading from /proc/stat.
1361 - irq: servicing interrupts
1362 - softirq: servicing softirqs
1363 - steal: involuntary wait
1364 - guest: running a normal guest
1365 - guest_nice: running a niced guest
1367 The "intr" line gives counts of interrupts serviced since boot time, for each
1368 of the possible system interrupts. The first column is the total of all
1369 interrupts serviced including unnumbered architecture specific interrupts;
1370 each subsequent column is the total for that particular numbered interrupt.
1371 Unnumbered interrupts are not shown, only summed into the total.
1373 The "ctxt" line gives the total number of context switches across all CPUs.
1375 The "btime" line gives the time at which the system booted, in seconds since
1378 The "processes" line gives the number of processes and threads created, which
1379 includes (but is not limited to) those created by calls to the fork() and
1380 clone() system calls.
1382 The "procs_running" line gives the total number of threads that are
1383 running or ready to run (i.e., the total number of runnable threads).
1385 The "procs_blocked" line gives the number of processes currently blocked,
1386 waiting for I/O to complete.
1388 The "softirq" line gives counts of softirqs serviced since boot time, for each
1389 of the possible system softirqs. The first column is the total of all
1390 softirqs serviced; each subsequent column is the total for that particular
1394 1.9 Ext4 file system parameters
1395 -------------------------------
1397 Information about mounted ext4 file systems can be found in
1398 /proc/fs/ext4. Each mounted filesystem will have a directory in
1399 /proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
1400 /proc/fs/ext4/dm-0). The files in each per-device directory are shown
1401 in Table 1-12, below.
1403 Table 1-12: Files in /proc/fs/ext4/<devname>
1404 ..............................................................................
1406 mb_groups details of multiblock allocator buddy cache of free blocks
1407 ..............................................................................
1411 Shows registered system console lines.
1413 To see which character device lines are currently used for the system console
1414 /dev/console, you may simply look into the file /proc/consoles:
1416 > cat /proc/consoles
1422 device name of the device
1423 operations R = can do read operations
1424 W = can do write operations
1426 flags E = it is enabled
1427 C = it is preferred console
1428 B = it is primary boot console
1429 p = it is used for printk buffer
1430 b = it is not a TTY but a Braille device
1431 a = it is safe to use when cpu is offline
1432 major:minor major and minor number of the device separated by a colon
1434 ------------------------------------------------------------------------------
1436 ------------------------------------------------------------------------------
1437 The /proc file system serves information about the running system. It not only
1438 allows access to process data but also allows you to request the kernel status
1439 by reading files in the hierarchy.
1441 The directory structure of /proc reflects the types of information and makes
1442 it easy, if not obvious, where to look for specific data.
1443 ------------------------------------------------------------------------------
1445 ------------------------------------------------------------------------------
1446 CHAPTER 2: MODIFYING SYSTEM PARAMETERS
1447 ------------------------------------------------------------------------------
1449 ------------------------------------------------------------------------------
1451 ------------------------------------------------------------------------------
1452 * Modifying kernel parameters by writing into files found in /proc/sys
1453 * Exploring the files which modify certain parameters
1454 * Review of the /proc/sys file tree
1455 ------------------------------------------------------------------------------
1458 A very interesting part of /proc is the directory /proc/sys. This is not only
1459 a source of information, it also allows you to change parameters within the
1460 kernel. Be very careful when attempting this. You can optimize your system,
1461 but you can also cause it to crash. Never alter kernel parameters on a
1462 production system. Set up a development machine and test to make sure that
1463 everything works the way you want it to. You may have no alternative but to
1464 reboot the machine once an error has been made.
1466 To change a value, simply echo the new value into the file. An example is
1467 given below in the section on the file system data. You need to be root to do
1468 this. You can create your own boot script to perform this every time your
1471 The files in /proc/sys can be used to fine tune and monitor miscellaneous and
1472 general things in the operation of the Linux kernel. Since some of the files
1473 can inadvertently disrupt your system, it is advisable to read both
1474 documentation and source before actually making adjustments. In any case, be
1475 very careful when writing to any of these files. The entries in /proc may
1476 change slightly between the 2.1.* and the 2.2 kernel, so if there is any doubt
1477 review the kernel documentation in the directory /usr/src/linux/Documentation.
1478 This chapter is heavily based on the documentation included in the pre 2.2
1479 kernels, and became part of it in version 2.2.1 of the Linux kernel.
1481 Please see: Documentation/sysctl/ directory for descriptions of these
1484 ------------------------------------------------------------------------------
1486 ------------------------------------------------------------------------------
1487 Certain aspects of kernel behavior can be modified at runtime, without the
1488 need to recompile the kernel, or even to reboot the system. The files in the
1489 /proc/sys tree can not only be read, but also modified. You can use the echo
1490 command to write value into these files, thereby changing the default settings
1492 ------------------------------------------------------------------------------
1494 ------------------------------------------------------------------------------
1495 CHAPTER 3: PER-PROCESS PARAMETERS
1496 ------------------------------------------------------------------------------
1498 3.1 /proc/<pid>/oom_adj & /proc/<pid>/oom_score_adj- Adjust the oom-killer score
1499 --------------------------------------------------------------------------------
1501 These file can be used to adjust the badness heuristic used to select which
1502 process gets killed in out of memory conditions.
1504 The badness heuristic assigns a value to each candidate task ranging from 0
1505 (never kill) to 1000 (always kill) to determine which process is targeted. The
1506 units are roughly a proportion along that range of allowed memory the process
1507 may allocate from based on an estimation of its current memory and swap use.
1508 For example, if a task is using all allowed memory, its badness score will be
1509 1000. If it is using half of its allowed memory, its score will be 500.
1511 There is an additional factor included in the badness score: the current memory
1512 and swap usage is discounted by 3% for root processes.
1514 The amount of "allowed" memory depends on the context in which the oom killer
1515 was called. If it is due to the memory assigned to the allocating task's cpuset
1516 being exhausted, the allowed memory represents the set of mems assigned to that
1517 cpuset. If it is due to a mempolicy's node(s) being exhausted, the allowed
1518 memory represents the set of mempolicy nodes. If it is due to a memory
1519 limit (or swap limit) being reached, the allowed memory is that configured
1520 limit. Finally, if it is due to the entire system being out of memory, the
1521 allowed memory represents all allocatable resources.
1523 The value of /proc/<pid>/oom_score_adj is added to the badness score before it
1524 is used to determine which task to kill. Acceptable values range from -1000
1525 (OOM_SCORE_ADJ_MIN) to +1000 (OOM_SCORE_ADJ_MAX). This allows userspace to
1526 polarize the preference for oom killing either by always preferring a certain
1527 task or completely disabling it. The lowest possible value, -1000, is
1528 equivalent to disabling oom killing entirely for that task since it will always
1529 report a badness score of 0.
1531 Consequently, it is very simple for userspace to define the amount of memory to
1532 consider for each task. Setting a /proc/<pid>/oom_score_adj value of +500, for
1533 example, is roughly equivalent to allowing the remainder of tasks sharing the
1534 same system, cpuset, mempolicy, or memory controller resources to use at least
1535 50% more memory. A value of -500, on the other hand, would be roughly
1536 equivalent to discounting 50% of the task's allowed memory from being considered
1537 as scoring against the task.
1539 For backwards compatibility with previous kernels, /proc/<pid>/oom_adj may also
1540 be used to tune the badness score. Its acceptable values range from -16
1541 (OOM_ADJUST_MIN) to +15 (OOM_ADJUST_MAX) and a special value of -17
1542 (OOM_DISABLE) to disable oom killing entirely for that task. Its value is
1543 scaled linearly with /proc/<pid>/oom_score_adj.
1545 The value of /proc/<pid>/oom_score_adj may be reduced no lower than the last
1546 value set by a CAP_SYS_RESOURCE process. To reduce the value any lower
1547 requires CAP_SYS_RESOURCE.
1549 Caveat: when a parent task is selected, the oom killer will sacrifice any first
1550 generation children with separate address spaces instead, if possible. This
1551 avoids servers and important system daemons from being killed and loses the
1552 minimal amount of work.
1555 3.2 /proc/<pid>/oom_score - Display current oom-killer score
1556 -------------------------------------------------------------
1558 This file can be used to check the current score used by the oom-killer is for
1559 any given <pid>. Use it together with /proc/<pid>/oom_score_adj to tune which
1560 process should be killed in an out-of-memory situation.
1563 3.3 /proc/<pid>/io - Display the IO accounting fields
1564 -------------------------------------------------------
1566 This file contains IO statistics for each running process
1571 test:/tmp # dd if=/dev/zero of=/tmp/test.dat &
1574 test:/tmp # cat /proc/3828/io
1580 write_bytes: 323932160
1581 cancelled_write_bytes: 0
1590 I/O counter: chars read
1591 The number of bytes which this task has caused to be read from storage. This
1592 is simply the sum of bytes which this process passed to read() and pread().
1593 It includes things like tty IO and it is unaffected by whether or not actual
1594 physical disk IO was required (the read might have been satisfied from
1601 I/O counter: chars written
1602 The number of bytes which this task has caused, or shall cause to be written
1603 to disk. Similar caveats apply here as with rchar.
1609 I/O counter: read syscalls
1610 Attempt to count the number of read I/O operations, i.e. syscalls like read()
1617 I/O counter: write syscalls
1618 Attempt to count the number of write I/O operations, i.e. syscalls like
1619 write() and pwrite().
1625 I/O counter: bytes read
1626 Attempt to count the number of bytes which this process really did cause to
1627 be fetched from the storage layer. Done at the submit_bio() level, so it is
1628 accurate for block-backed filesystems. <please add status regarding NFS and
1629 CIFS at a later time>
1635 I/O counter: bytes written
1636 Attempt to count the number of bytes which this process caused to be sent to
1637 the storage layer. This is done at page-dirtying time.
1640 cancelled_write_bytes
1641 ---------------------
1643 The big inaccuracy here is truncate. If a process writes 1MB to a file and
1644 then deletes the file, it will in fact perform no writeout. But it will have
1645 been accounted as having caused 1MB of write.
1646 In other words: The number of bytes which this process caused to not happen,
1647 by truncating pagecache. A task can cause "negative" IO too. If this task
1648 truncates some dirty pagecache, some IO which another task has been accounted
1649 for (in its write_bytes) will not be happening. We _could_ just subtract that
1650 from the truncating task's write_bytes, but there is information loss in doing
1657 At its current implementation state, this is a bit racy on 32-bit machines: if
1658 process A reads process B's /proc/pid/io while process B is updating one of
1659 those 64-bit counters, process A could see an intermediate result.
1662 More information about this can be found within the taskstats documentation in
1663 Documentation/accounting.
1665 3.4 /proc/<pid>/coredump_filter - Core dump filtering settings
1666 ---------------------------------------------------------------
1667 When a process is dumped, all anonymous memory is written to a core file as
1668 long as the size of the core file isn't limited. But sometimes we don't want
1669 to dump some memory segments, for example, huge shared memory or DAX.
1670 Conversely, sometimes we want to save file-backed memory segments into a core
1671 file, not only the individual files.
1673 /proc/<pid>/coredump_filter allows you to customize which memory segments
1674 will be dumped when the <pid> process is dumped. coredump_filter is a bitmask
1675 of memory types. If a bit of the bitmask is set, memory segments of the
1676 corresponding memory type are dumped, otherwise they are not dumped.
1678 The following 9 memory types are supported:
1679 - (bit 0) anonymous private memory
1680 - (bit 1) anonymous shared memory
1681 - (bit 2) file-backed private memory
1682 - (bit 3) file-backed shared memory
1683 - (bit 4) ELF header pages in file-backed private memory areas (it is
1684 effective only if the bit 2 is cleared)
1685 - (bit 5) hugetlb private memory
1686 - (bit 6) hugetlb shared memory
1687 - (bit 7) DAX private memory
1688 - (bit 8) DAX shared memory
1690 Note that MMIO pages such as frame buffer are never dumped and vDSO pages
1691 are always dumped regardless of the bitmask status.
1693 Note that bits 0-4 don't affect hugetlb or DAX memory. hugetlb memory is
1694 only affected by bit 5-6, and DAX is only affected by bits 7-8.
1696 The default value of coredump_filter is 0x33; this means all anonymous memory
1697 segments, ELF header pages and hugetlb private memory are dumped.
1699 If you don't want to dump all shared memory segments attached to pid 1234,
1700 write 0x31 to the process's proc file.
1702 $ echo 0x31 > /proc/1234/coredump_filter
1704 When a new process is created, the process inherits the bitmask status from its
1705 parent. It is useful to set up coredump_filter before the program runs.
1708 $ echo 0x7 > /proc/self/coredump_filter
1711 3.5 /proc/<pid>/mountinfo - Information about mounts
1712 --------------------------------------------------------
1714 This file contains lines of the form:
1716 36 35 98:0 /mnt1 /mnt2 rw,noatime master:1 - ext3 /dev/root rw,errors=continue
1717 (1)(2)(3) (4) (5) (6) (7) (8) (9) (10) (11)
1719 (1) mount ID: unique identifier of the mount (may be reused after umount)
1720 (2) parent ID: ID of parent (or of self for the top of the mount tree)
1721 (3) major:minor: value of st_dev for files on filesystem
1722 (4) root: root of the mount within the filesystem
1723 (5) mount point: mount point relative to the process's root
1724 (6) mount options: per mount options
1725 (7) optional fields: zero or more fields of the form "tag[:value]"
1726 (8) separator: marks the end of the optional fields
1727 (9) filesystem type: name of filesystem of the form "type[.subtype]"
1728 (10) mount source: filesystem specific information or "none"
1729 (11) super options: per super block options
1731 Parsers should ignore all unrecognised optional fields. Currently the
1732 possible optional fields are:
1734 shared:X mount is shared in peer group X
1735 master:X mount is slave to peer group X
1736 propagate_from:X mount is slave and receives propagation from peer group X (*)
1737 unbindable mount is unbindable
1739 (*) X is the closest dominant peer group under the process's root. If
1740 X is the immediate master of the mount, or if there's no dominant peer
1741 group under the same root, then only the "master:X" field is present
1742 and not the "propagate_from:X" field.
1744 For more information on mount propagation see:
1746 Documentation/filesystems/sharedsubtree.txt
1749 3.6 /proc/<pid>/comm & /proc/<pid>/task/<tid>/comm
1750 --------------------------------------------------------
1751 These files provide a method to access a tasks comm value. It also allows for
1752 a task to set its own or one of its thread siblings comm value. The comm value
1753 is limited in size compared to the cmdline value, so writing anything longer
1754 then the kernel's TASK_COMM_LEN (currently 16 chars) will result in a truncated
1758 3.7 /proc/<pid>/task/<tid>/children - Information about task children
1759 -------------------------------------------------------------------------
1760 This file provides a fast way to retrieve first level children pids
1761 of a task pointed by <pid>/<tid> pair. The format is a space separated
1764 Note the "first level" here -- if a child has own children they will
1765 not be listed here, one needs to read /proc/<children-pid>/task/<tid>/children
1766 to obtain the descendants.
1768 Since this interface is intended to be fast and cheap it doesn't
1769 guarantee to provide precise results and some children might be
1770 skipped, especially if they've exited right after we printed their
1771 pids, so one need to either stop or freeze processes being inspected
1772 if precise results are needed.
1775 3.8 /proc/<pid>/fdinfo/<fd> - Information about opened file
1776 ---------------------------------------------------------------
1777 This file provides information associated with an opened file. The regular
1778 files have at least three fields -- 'pos', 'flags' and mnt_id. The 'pos'
1779 represents the current offset of the opened file in decimal form [see lseek(2)
1780 for details], 'flags' denotes the octal O_xxx mask the file has been
1781 created with [see open(2) for details] and 'mnt_id' represents mount ID of
1782 the file system containing the opened file [see 3.5 /proc/<pid>/mountinfo
1791 All locks associated with a file descriptor are shown in its fdinfo too.
1793 lock: 1: FLOCK ADVISORY WRITE 359 00:13:11691 0 EOF
1795 The files such as eventfd, fsnotify, signalfd, epoll among the regular pos/flags
1796 pair provide additional information particular to the objects they represent.
1805 where 'eventfd-count' is hex value of a counter.
1812 sigmask: 0000000000000200
1814 where 'sigmask' is hex value of the signal mask associated
1822 tfd: 5 events: 1d data: ffffffffffffffff pos:0 ino:61af sdev:7
1824 where 'tfd' is a target file descriptor number in decimal form,
1825 'events' is events mask being watched and the 'data' is data
1826 associated with a target [see epoll(7) for more details].
1828 The 'pos' is current offset of the target file in decimal form
1829 [see lseek(2)], 'ino' and 'sdev' are inode and device numbers
1830 where target file resides, all in hex format.
1834 For inotify files the format is the following
1838 inotify wd:3 ino:9e7e sdev:800013 mask:800afce ignored_mask:0 fhandle-bytes:8 fhandle-type:1 f_handle:7e9e0000640d1b6d
1840 where 'wd' is a watch descriptor in decimal form, ie a target file
1841 descriptor number, 'ino' and 'sdev' are inode and device where the
1842 target file resides and the 'mask' is the mask of events, all in hex
1843 form [see inotify(7) for more details].
1845 If the kernel was built with exportfs support, the path to the target
1846 file is encoded as a file handle. The file handle is provided by three
1847 fields 'fhandle-bytes', 'fhandle-type' and 'f_handle', all in hex
1850 If the kernel is built without exportfs support the file handle won't be
1853 If there is no inotify mark attached yet the 'inotify' line will be omitted.
1855 For fanotify files the format is
1860 fanotify flags:10 event-flags:0
1861 fanotify mnt_id:12 mflags:40 mask:38 ignored_mask:40000003
1862 fanotify ino:4f969 sdev:800013 mflags:0 mask:3b ignored_mask:40000000 fhandle-bytes:8 fhandle-type:1 f_handle:69f90400c275b5b4
1864 where fanotify 'flags' and 'event-flags' are values used in fanotify_init
1865 call, 'mnt_id' is the mount point identifier, 'mflags' is the value of
1866 flags associated with mark which are tracked separately from events
1867 mask. 'ino', 'sdev' are target inode and device, 'mask' is the events
1868 mask and 'ignored_mask' is the mask of events which are to be ignored.
1869 All in hex format. Incorporation of 'mflags', 'mask' and 'ignored_mask'
1870 does provide information about flags and mask used in fanotify_mark
1871 call [see fsnotify manpage for details].
1873 While the first three lines are mandatory and always printed, the rest is
1874 optional and may be omitted if no marks created yet.
1885 it_value: (0, 49406829)
1888 where 'clockid' is the clock type and 'ticks' is the number of the timer expirations
1889 that have occurred [see timerfd_create(2) for details]. 'settime flags' are
1890 flags in octal form been used to setup the timer [see timerfd_settime(2) for
1891 details]. 'it_value' is remaining time until the timer exiration.
1892 'it_interval' is the interval for the timer. Note the timer might be set up
1893 with TIMER_ABSTIME option which will be shown in 'settime flags', but 'it_value'
1894 still exhibits timer's remaining time.
1896 3.9 /proc/<pid>/map_files - Information about memory mapped files
1897 ---------------------------------------------------------------------
1898 This directory contains symbolic links which represent memory mapped files
1899 the process is maintaining. Example output:
1901 | lr-------- 1 root root 64 Jan 27 11:24 333c600000-333c620000 -> /usr/lib64/ld-2.18.so
1902 | lr-------- 1 root root 64 Jan 27 11:24 333c81f000-333c820000 -> /usr/lib64/ld-2.18.so
1903 | lr-------- 1 root root 64 Jan 27 11:24 333c820000-333c821000 -> /usr/lib64/ld-2.18.so
1905 | lr-------- 1 root root 64 Jan 27 11:24 35d0421000-35d0422000 -> /usr/lib64/libselinux.so.1
1906 | lr-------- 1 root root 64 Jan 27 11:24 400000-41a000 -> /usr/bin/ls
1908 The name of a link represents the virtual memory bounds of a mapping, i.e.
1909 vm_area_struct::vm_start-vm_area_struct::vm_end.
1911 The main purpose of the map_files is to retrieve a set of memory mapped
1912 files in a fast way instead of parsing /proc/<pid>/maps or
1913 /proc/<pid>/smaps, both of which contain many more records. At the same
1914 time one can open(2) mappings from the listings of two processes and
1915 comparing their inode numbers to figure out which anonymous memory areas
1916 are actually shared.
1918 3.10 /proc/<pid>/timerslack_ns - Task timerslack value
1919 ---------------------------------------------------------
1920 This file provides the value of the task's timerslack value in nanoseconds.
1921 This value specifies a amount of time that normal timers may be deferred
1922 in order to coalesce timers and avoid unnecessary wakeups.
1924 This allows a task's interactivity vs power consumption trade off to be
1927 Writing 0 to the file will set the tasks timerslack to the default value.
1929 Valid values are from 0 - ULLONG_MAX
1931 An application setting the value must have PTRACE_MODE_ATTACH_FSCREDS level
1932 permissions on the task specified to change its timerslack_ns value.
1934 3.11 /proc/<pid>/patch_state - Livepatch patch operation state
1935 -----------------------------------------------------------------
1936 When CONFIG_LIVEPATCH is enabled, this file displays the value of the
1937 patch state for the task.
1939 A value of '-1' indicates that no patch is in transition.
1941 A value of '0' indicates that a patch is in transition and the task is
1942 unpatched. If the patch is being enabled, then the task hasn't been
1943 patched yet. If the patch is being disabled, then the task has already
1946 A value of '1' indicates that a patch is in transition and the task is
1947 patched. If the patch is being enabled, then the task has already been
1948 patched. If the patch is being disabled, then the task hasn't been
1952 ------------------------------------------------------------------------------
1954 ------------------------------------------------------------------------------
1957 ---------------------
1959 The following mount options are supported:
1961 hidepid= Set /proc/<pid>/ access mode.
1962 gid= Set the group authorized to learn processes information.
1964 hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories
1967 hidepid=1 means users may not access any /proc/<pid>/ directories but their
1968 own. Sensitive files like cmdline, sched*, status are now protected against
1969 other users. This makes it impossible to learn whether any user runs
1970 specific program (given the program doesn't reveal itself by its behaviour).
1971 As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users,
1972 poorly written programs passing sensitive information via program arguments are
1973 now protected against local eavesdroppers.
1975 hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other
1976 users. It doesn't mean that it hides a fact whether a process with a specific
1977 pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"),
1978 but it hides process' uid and gid, which may be learned by stat()'ing
1979 /proc/<pid>/ otherwise. It greatly complicates an intruder's task of gathering
1980 information about running processes, whether some daemon runs with elevated
1981 privileges, whether other user runs some sensitive program, whether other users
1982 run any program at all, etc.
1984 gid= defines a group authorized to learn processes information otherwise
1985 prohibited by hidepid=. If you use some daemon like identd which needs to learn
1986 information about processes information, just add identd to this group.
git.samba.org / sfrench / cifs-2.6.git / blob