proc.5, proc_pid_status.5: Split /proc/PID/status from proc(5)

[thirdparty/man-pages.git] / man5 / proc.5

'\" t
.\" Copyright (C) 1994, 1995, Daniel Quinlan <quinlan@yggdrasil.com>
.\" Copyright (C) 2002-2008, 2017, Michael Kerrisk <mtk.manpages@gmail.com>
.\" and scsi additions from Michael Neuffer (neuffer@mail.uni-mainz.de)
.\" and sysctl additions from Andries Brouwer (aeb@cwi.nl)
.\" and System V IPC (as well as various other) additions from
.\" Michael Kerrisk <mtk.manpages@gmail.com>
.\"
.\" SPDX-License-Identifier: GPL-2.0-or-later
.\"
.\" Modified 1995-05-17 by faith@cs.unc.edu
.\" Minor changes by aeb and Marty Leisner (leisner@sdsp.mc.xerox.com).
.\" Modified 1996-04-13, 1996-07-22 by aeb@cwi.nl
.\" Modified 2001-12-16 by rwhron@earthlink.net
.\" Modified 2002-07-13 by jbelton@shaw.ca
.\" Modified 2002-07-22, 2003-05-27, 2004-04-06, 2004-05-25
.\"    by Michael Kerrisk <mtk.manpages@gmail.com>
.\" 2004-11-17, mtk -- updated notes on /proc/loadavg
.\" 2004-12-01, mtk, rtsig-max and rtsig-nr went away in Linux 2.6.8
.\" 2004-12-14, mtk, updated 'statm', and fixed error in order of list
.\" 2005-05-12, mtk, updated 'stat'
.\" 2005-07-13, mtk, added /proc/sys/fs/mqueue/*
.\" 2005-09-16, mtk, Added /proc/sys/fs/suid_dumpable
.\" 2005-09-19, mtk, added /proc/zoneinfo
.\" 2005-03-01, mtk, moved /proc/sys/fs/mqueue/* material to mq_overview.7.
.\" 2008-06-05, mtk, Added /proc/[pid]/oom_score, /proc/[pid]/oom_adj,
.\"     /proc/[pid]/limits, /proc/[pid]/mountinfo, /proc/[pid]/mountstats,
.\"     and /proc/[pid]/fdinfo/*.
.\" 2008-06-19, mtk, Documented /proc/[pid]/status.
.\" 2008-07-15, mtk, added /proc/config.gz
.\"
.\" FIXME cross check against Documentation/filesystems/proc.txt
.\" to see what information could be imported from that file
.\" into this file.
.\"
.TH proc 5 (date) "Linux man-pages (unreleased)"
.SH NAME
proc \- process information, system information, and sysctl pseudo-filesystem
.SH DESCRIPTION
The
.B proc
filesystem is a pseudo-filesystem which provides an interface to
kernel data structures.
It is commonly mounted at
.IR /proc .
Typically, it is mounted automatically by the system,
but it can also be mounted manually using a command such as:
.PP
.in +4n
.EX
mount \-t proc proc /proc
.EE
.in
.PP
Most of the files in the
.B proc
filesystem are read-only,
but some files are writable, allowing kernel variables to be changed.
.\"
.SS Mount options
The
.B proc
filesystem supports the following mount options:
.TP
.BR hidepid "=\fIn\fP (since Linux 3.3)"
.\" commit 0499680a42141d86417a8fbaa8c8db806bea1201
This option controls who can access the information in
.IR /proc/ pid
directories.
The argument,
.IR n ,
is one of the following values:
.RS
.TP 4
0
Everybody may access all
.IR /proc/ pid
directories.
This is the traditional behavior,
and the default if this mount option is not specified.
.TP
1
Users may not access files and subdirectories inside any
.IR /proc/ pid
directories but their own (the
.IR /proc/ pid
directories themselves remain visible).
Sensitive files such as
.IR /proc/ pid /cmdline
and
.IR /proc/ pid /status
are now protected against other users.
This makes it impossible to learn whether any user is running a
specific program
(so long as the program doesn't otherwise reveal itself by its behavior).
.\" As an additional bonus, since
.\" .IR /proc/[pid]/cmdline
.\" is inaccessible for other users,
.\" poorly written programs passing sensitive information via
.\" program arguments are now protected against local eavesdroppers.
.TP
2
As for mode 1, but in addition the
.IR /proc/ pid
directories belonging to other users become invisible.
This means that
.IR /proc/ pid
entries can no longer be used to discover the PIDs on the system.
This doesn't hide the fact that a process with a specific PID value exists
(it can be learned by other means, for example, by "kill \-0 $PID"),
but it hides a process's UID and GID,
which could otherwise be learned by employing
.BR stat (2)
on a
.IR /proc/ pid
directory.
This greatly complicates an attacker's task of gathering
information about running processes (e.g., discovering whether
some daemon is running with elevated privileges,
whether another user is running some sensitive program,
whether other users are running any program at all, and so on).
.RE
.TP
.BR gid "=\fIgid\fP (since Linux 3.3)"
.\" commit 0499680a42141d86417a8fbaa8c8db806bea1201
Specifies the ID of a group whose members are authorized to
learn process information otherwise prohibited by
.B hidepid
(i.e., users in this group behave as though
.I /proc
was mounted with
.IR hidepid=0 ).
This group should be used instead of approaches such as putting
nonroot users into the
.BR sudoers (5)
file.
.\"
.SS Overview
Underneath
.IR /proc ,
there are the following general groups of files and subdirectories:
.TP
.IR /proc/ "pid subdirectories"
Each one of these subdirectories contains files and subdirectories
exposing information about the process with the corresponding process ID.
.IP
Underneath each of the
.IR /proc/ pid
directories, a
.I task
subdirectory contains subdirectories of the form
.IR task/ tid,
which contain corresponding information about each of the threads
in the process, where
.I tid
is the kernel thread ID of the thread.
.IP
The
.IR /proc/ pid
subdirectories are visible when iterating through
.I /proc
with
.BR getdents (2)
(and thus are visible when one uses
.BR ls (1)
to view the contents of
.IR /proc ).
.TP
.IR /proc/ "tid subdirectories"
Each one of these subdirectories contains files and subdirectories
exposing information about the thread with the corresponding thread ID.
The contents of these directories are the same as the corresponding
.IR /proc/ pid /task/ tid
directories.
.IP
The
.IR /proc/ tid
subdirectories are
.I not
visible when iterating through
.I /proc
with
.BR getdents (2)
(and thus are
.I not
visible when one uses
.BR ls (1)
to view the contents of
.IR /proc ).
.TP
.I /proc/self
When a process accesses this magic symbolic link,
it resolves to the process's own
.IR /proc/ pid
directory.
.TP
.I /proc/thread\-self
When a thread accesses this magic symbolic link,
it resolves to the process's own
.IR /proc/self/task/ tid
directory.
.TP
.I /proc/[a\-z]*
Various other files and subdirectories under
.I /proc
expose system-wide information.
.PP
All of the above are described in more detail below.
.\"
.SS Files and directories
The following list provides details of many of the files and directories
under the
.I /proc
hierarchy.
.TP
.IR /proc/ pid
There is a numerical subdirectory for each running process; the
subdirectory is named by the process ID.
Each
.IR /proc/ pid
subdirectory contains the pseudo-files and directories described below.
.IP
The files inside each
.IR /proc/ pid
directory are normally owned by the effective user and
effective group ID of the process.
However, as a security measure, the ownership is made
.I root:root
if the process's "dumpable" attribute is set to a value other than 1.
.IP
Before Linux 4.11,
.\" commit 68eb94f16227336a5773b83ecfa8290f1d6b78ce
.I root:root
meant the "global" root user ID and group ID
(i.e., UID 0 and GID 0 in the initial user namespace).
Since Linux 4.11,
if the process is in a noninitial user namespace that has a
valid mapping for user (group) ID 0 inside the namespace, then
the user (group) ownership of the files under
.IR /proc/ pid
is instead made the same as the root user (group) ID of the namespace.
This means that inside a container,
things work as expected for the container "root" user.
.IP
The process's "dumpable" attribute may change for the following reasons:
.RS
.IP \[bu] 3
The attribute was explicitly set via the
.BR prctl (2)
.B PR_SET_DUMPABLE
operation.
.IP \[bu]
The attribute was reset to the value in the file
.I /proc/sys/fs/suid_dumpable
(described below), for the reasons described in
.BR prctl (2).
.RE
.IP
Resetting the "dumpable" attribute to 1 reverts the ownership of the
.IR /proc/ pid /*
files to the process's effective UID and GID.
Note, however, that if the effective UID or GID is subsequently modified,
then the "dumpable" attribute may be reset, as described in
.BR prctl (2).
Therefore, it may be desirable to reset the "dumpable" attribute
.I after
making any desired changes to the process's effective UID or GID.
.\" FIXME Describe /proc/[pid]/sessionid
.\"	  commit 1e0bd7550ea9cf474b1ad4c6ff5729a507f75fdc
.\"       CONFIG_AUDITSYSCALL
.\"       Added in Linux 2.6.25; read-only; only readable by real UID
.\"
.\" FIXME Describe /proc/[pid]/sched
.\"       Added in Linux 2.6.23
.\"       CONFIG_SCHED_DEBUG, and additional fields if CONFIG_SCHEDSTATS
.\"       Displays various scheduling parameters
.\"       This file can be written, to reset stats
.\"       The set of fields exposed by this file have changed
.\"	  significantly over time.
.\"       commit 43ae34cb4cd650d1eb4460a8253a8e747ba052ac
.\"
.\" FIXME Describe /proc/[pid]/schedstats and
.\"       /proc/[pid]/task/[tid]/schedstats
.\"       Added in Linux 2.6.9
.\"       CONFIG_SCHEDSTATS
.TP
.IR /proc/ pid /syscall " (since Linux 2.6.27)"
.\" commit ebcb67341fee34061430f3367f2e507e52ee051b
This file exposes the system call number and argument registers for the
system call currently being executed by the process,
followed by the values of the stack pointer and program counter registers.
The values of all six argument registers are exposed,
although most system calls use fewer registers.
.IP
If the process is blocked, but not in a system call,
then the file displays \-1 in place of the system call number,
followed by just the values of the stack pointer and program counter.
If process is not blocked, then the file contains just the string "running".
.IP
This file is present only if the kernel was configured with
.BR CONFIG_HAVE_ARCH_TRACEHOOK .
.IP
Permission to access this file is governed by a ptrace access mode
.B PTRACE_MODE_ATTACH_FSCREDS
check; see
.BR ptrace (2).
.TP
.IR /proc/ pid /task " (since Linux 2.6.0)"
.\" Precisely: Linux 2.6.0-test6
This is a directory that contains one subdirectory
for each thread in the process.
The name of each subdirectory is the numerical thread ID
.RI ( tid )
of the thread (see
.BR gettid (2)).
.IP
Within each of these subdirectories, there is a set of
files with the same names and contents as under the
.IR /proc/ pid
directories.
For attributes that are shared by all threads, the contents for
each of the files under the
.IR task/ tid
subdirectories will be the same as in the corresponding
file in the parent
.IR /proc/ pid
directory
(e.g., in a multithreaded process, all of the
.IR task/ tid /cwd
files will have the same value as the
.IR /proc/ pid /cwd
file in the parent directory, since all of the threads in a process
share a working directory).
For attributes that are distinct for each thread,
the corresponding files under
.IR task/ tid
may have different values (e.g., various fields in each of the
.IR task/ tid /status
files may be different for each thread),
.\" in particular: "children" :/
or they might not exist in
.IR /proc/ pid
at all.
.IP
.\" The following was still true as at kernel 2.6.13
In a multithreaded process, the contents of the
.IR /proc/ pid /task
directory are not available if the main thread has already terminated
(typically by calling
.BR pthread_exit (3)).
.TP
.IR /proc/ pid /task/ tid /children " (since Linux 3.5)"
.\" commit 818411616baf46ceba0cff6f05af3a9b294734f7
A space-separated list of child tasks of this task.
Each child task is represented by its TID.
.IP
.\" see comments in get_children_pid() in fs/proc/array.c
This option is intended for use by the checkpoint-restore (CRIU) system,
and reliably provides a list of children only if all of the child processes
are stopped or frozen.
It does not work properly if children of the target task exit while
the file is being read!
Exiting children may cause non-exiting children to be omitted from the list.
This makes this interface even more unreliable than classic PID-based
approaches if the inspected task and its children aren't frozen,
and most code should probably not use this interface.
.IP
Until Linux 4.2, the presence of this file was governed by the
.B CONFIG_CHECKPOINT_RESTORE
kernel configuration option.
Since Linux 4.2,
.\" commit 2e13ba54a2682eea24918b87ad3edf70c2cf085b
it is governed by the
.B CONFIG_PROC_CHILDREN
option.
.TP
.IR /proc/ pid /timers " (since Linux 3.10)"
.\" commit 5ed67f05f66c41e39880a6d61358438a25f9fee5
.\" commit 48f6a7a511ef8823fdff39afee0320092d43a8a0
A list of the POSIX timers for this process.
Each timer is listed with a line that starts with the string "ID:".
For example:
.IP
.in +4n
.EX
ID: 1
signal: 60/00007fff86e452a8
notify: signal/pid.2634
ClockID: 0
ID: 0
signal: 60/00007fff86e452a8
notify: signal/pid.2634
ClockID: 1
.EE
.in
.IP
The lines shown for each timer have the following meanings:
.RS
.TP
.I ID
The ID for this timer.
This is not the same as the timer ID returned by
.BR timer_create (2);
rather, it is the same kernel-internal ID that is available via the
.I si_timerid
field of the
.I siginfo_t
structure (see
.BR sigaction (2)).
.TP
.I signal
This is the signal number that this timer uses to deliver notifications
followed by a slash, and then the
.I sigev_value
value supplied to the signal handler.
Valid only for timers that notify via a signal.
.TP
.I notify
The part before the slash specifies the mechanism
that this timer uses to deliver notifications,
and is one of "thread", "signal", or "none".
Immediately following the slash is either the string "tid" for timers
with
.B SIGEV_THREAD_ID
notification, or "pid" for timers that notify by other mechanisms.
Following the "." is the PID of the process
(or the kernel thread ID of the thread)  that will be delivered
a signal if the timer delivers notifications via a signal.
.TP
.I ClockID
This field identifies the clock that the timer uses for measuring time.
For most clocks, this is a number that matches one of the user-space
.B CLOCK_*
constants exposed via
.IR <time.h> .
.B CLOCK_PROCESS_CPUTIME_ID
timers display with a value of \-6
in this field.
.B CLOCK_THREAD_CPUTIME_ID
timers display with a value of \-2
in this field.
.RE
.IP
This file is available only when the kernel was configured with
.BR CONFIG_CHECKPOINT_RESTORE .
.TP
.IR /proc/ pid /timerslack_ns " (since Linux 4.6)"
.\" commit da8b44d5a9f8bf26da637b7336508ca534d6b319
.\" commit 5de23d435e88996b1efe0e2cebe242074ce67c9e
This file exposes the process's "current" timer slack value,
expressed in nanoseconds.
The file is writable,
allowing the process's timer slack value to be changed.
Writing 0 to this file resets the "current" timer slack to the
"default" timer slack value.
For further details, see the discussion of
.B PR_SET_TIMERSLACK
in
.BR prctl (2).
.IP
Initially,
permission to access this file was governed by a ptrace access mode
.B PTRACE_MODE_ATTACH_FSCREDS
check (see
.BR ptrace (2)).
However, this was subsequently deemed too strict a requirement
(and had the side effect that requiring a process to have the
.B CAP_SYS_PTRACE
capability would also allow it to view and change any process's memory).
Therefore, since Linux 4.9,
.\" commit 7abbaf94049914f074306d960b0f968ffe52e59f
only the (weaker)
.B CAP_SYS_NICE
capability is required to access this file.
.TP
.IR /proc/ pid /wchan " (since Linux 2.6.0)"
The symbolic name corresponding to the location
in the kernel where the process is sleeping.
.IP
Permission to access this file is governed by a ptrace access mode
.B PTRACE_MODE_READ_FSCREDS
check; see
.BR ptrace (2).
.TP
.IR /proc/ tid
There  is a numerical subdirectory for each running thread
that is not a thread group leader
(i.e., a thread whose thread ID is not the same as its process ID);
the subdirectory is named by the thread ID.
Each one of these subdirectories contains files and subdirectories
exposing information about the thread with the thread ID
.IR tid .
The contents of these directories are the same as the corresponding
.IR /proc/ pid /task/ tid
directories.
.IP
The
.IR /proc/ tid
subdirectories are
.I not
visible when iterating through
.I /proc
with
.BR getdents (2)
(and thus are
.I not
visible when one uses
.BR ls (1)
to view the contents of
.IR /proc ).
However, the pathnames of these directories are visible to
(i.e., usable as arguments in)
system calls that operate on pathnames.
.TP
.I /proc/apm
Advanced power management version and battery information when
.B CONFIG_APM
is defined at kernel compilation time.
.TP
.I /proc/buddyinfo
This file contains information which is used for diagnosing memory
fragmentation issues.
Each line starts with the identification of the node and the name
of the zone which together identify a memory region.
This is then
followed by the count of available chunks of a certain order in
which these zones are split.
The size in bytes of a certain order is given by the formula:
.IP
.in +4n
.EX
(2\[ha]order)\ *\ PAGE_SIZE
.EE
.in
.IP
The binary buddy allocator algorithm inside the kernel will split
one chunk into two chunks of a smaller order (thus with half the
size) or combine two contiguous chunks into one larger chunk of
a higher order (thus with double the size) to satisfy allocation
requests and to counter memory fragmentation.
The order matches the column number, when starting to count at zero.
.IP
For example on an x86-64 system:
.RS -12
.EX
Node 0, zone     DMA     1    1    1    0    2    1    1    0    1    1    3
Node 0, zone   DMA32    65   47    4   81   52   28   13   10    5    1  404
Node 0, zone  Normal   216   55  189  101   84   38   37   27    5    3  587
.EE
.RE
.IP
In this example, there is one node containing three zones and there
are 11 different chunk sizes.
If the page size is 4 kilobytes, then the first zone called
.I DMA
(on x86 the first 16 megabyte of memory) has 1 chunk of 4 kilobytes
(order 0) available and has 3 chunks of 4 megabytes (order 10) available.
.IP
If the memory is heavily fragmented, the counters for higher
order chunks will be zero and allocation of large contiguous areas
will fail.
.IP
Further information about the zones can be found in
.IR /proc/zoneinfo .
.TP
.I /proc/bus
Contains subdirectories for installed buses.
.TP
.I /proc/bus/pccard
Subdirectory for PCMCIA devices when
.B CONFIG_PCMCIA
is set at kernel compilation time.
.TP
.I /proc/bus/pccard/drivers
.TP
.I /proc/bus/pci
Contains various bus subdirectories and pseudo-files containing
information about PCI buses, installed devices, and device
drivers.
Some of these files are not ASCII.
.TP
.I /proc/bus/pci/devices
Information about PCI devices.
They may be accessed through
.BR lspci (8)
and
.BR setpci (8).
.TP
.IR /proc/cgroups " (since Linux 2.6.24)"
See
.BR cgroups (7).
.TP
.I /proc/cmdline
Arguments passed to the Linux kernel at boot time.
Often done via a boot manager such as
.BR lilo (8)
or
.BR grub (8).
Any arguments embedded in the kernel image or initramfs via
.B CONFIG_BOOT_CONFIG
will also be displayed.
.TP
.IR /proc/config.gz " (since Linux 2.6)"
This file exposes the configuration options that were used
to build the currently running kernel,
in the same format as they would be shown in the
.I .config
file that resulted when configuring the kernel (using
.IR "make xconfig" ,
.IR "make config" ,
or similar).
The file contents are compressed; view or search them using
.BR zcat (1)
and
.BR zgrep (1).
As long as no changes have been made to the following file,
the contents of
.I /proc/config.gz
are the same as those provided by:
.IP
.in +4n
.EX
cat /lib/modules/$(uname \-r)/build/.config
.EE
.in
.IP
.I /proc/config.gz
is provided only if the kernel is configured with
.BR CONFIG_IKCONFIG_PROC .
.TP
.I /proc/crypto
A list of the ciphers provided by the kernel crypto API.
For details, see the kernel
.I "Linux Kernel Crypto API"
documentation available under the kernel source directory
.I Documentation/crypto/
.\" commit 3b72c814a8e8cd638e1ba0da4dfce501e9dff5af
(or
.I Documentation/DocBook
before Linux 4.10;
the documentation can be built using a command such as
.I make htmldocs
in the root directory of the kernel source tree).
.TP
.I /proc/cpuinfo
This is a collection of CPU and system architecture dependent items,
for each supported architecture a different list.
Two common entries are \fIprocessor\fP which gives CPU number and
\fIbogomips\fP; a system constant that is calculated
during kernel initialization.
SMP machines have information for
each CPU.
The
.BR lscpu (1)
command gathers its information from this file.
.TP
.I /proc/devices
Text listing of major numbers and device groups.
This can be used by MAKEDEV scripts for consistency with the kernel.
.TP
.IR /proc/diskstats " (since Linux 2.5.69)"
This file contains disk I/O statistics for each disk device.
See the Linux kernel source file
.I Documentation/admin\-guide/iostats.rst
(or
.I Documentation/iostats.txt
before Linux 5.3)
for further information.
.TP
.I /proc/dma
This is a list of the registered \fIISA\fP DMA (direct memory access)
channels in use.
.TP
.I /proc/driver
Empty subdirectory.
.TP
.I /proc/execdomains
Used to list ABI personalities before Linux 4.1;
now contains a constant string for userspace compatibility.
.TP
.I /proc/fb
Frame buffer information when
.B CONFIG_FB
is defined during kernel compilation.
.TP
.I /proc/filesystems
A text listing of the filesystems which are supported by the kernel,
namely filesystems which were compiled into the kernel or whose kernel
modules are currently loaded.
(See also
.BR filesystems (5).)
If a filesystem is marked with "nodev",
this means that it does not require a block device to be mounted
(e.g., virtual filesystem, network filesystem).
.IP
Incidentally, this file may be used by
.BR mount (8)
when no filesystem is specified and it didn't manage to determine the
filesystem type.
Then filesystems contained in this file are tried
(excepted those that are marked with "nodev").
.TP
.I /proc/fs
.\" FIXME Much more needs to be said about /proc/fs
.\"
Contains subdirectories that in turn contain files
with information about (certain) mounted filesystems.
.TP
.I /proc/ide
This directory
exists on systems with the IDE bus.
There are directories for each IDE channel and attached device.
Files include:
.IP
.in +4n
.EX
cache              buffer size in KB
capacity           number of sectors
driver             driver version
geometry           physical and logical geometry
identify           in hexadecimal
media              media type
model              manufacturer\[aq]s model number
settings           drive settings
smart_thresholds   IDE disk management thresholds (in hex)
smart_values       IDE disk management values (in hex)
.EE
.in
.IP
The
.BR hdparm (8)
utility provides access to this information in a friendly format.
.TP
.I /proc/interrupts
This is used to record the number of interrupts per CPU per IO device.
Since Linux 2.6.24,
for the i386 and x86-64 architectures, at least, this also includes
interrupts internal to the system (that is, not associated with a device
as such), such as NMI (nonmaskable interrupt), LOC (local timer interrupt),
and for SMP systems, TLB (TLB flush interrupt), RES (rescheduling
interrupt), CAL (remote function call interrupt), and possibly others.
Very easy to read formatting, done in ASCII.
.TP
.I /proc/iomem
I/O memory map in Linux 2.4.
.TP
.I /proc/ioports
This is a list of currently registered Input-Output port regions that
are in use.
.TP
.IR /proc/kallsyms " (since Linux 2.5.71)"
This holds the kernel exported symbol definitions used by the
.BR modules (X)
tools to dynamically link and bind loadable modules.
In Linux 2.5.47 and earlier, a similar file with slightly different syntax
was named
.IR ksyms .
.TP
.I /proc/kcore
This file represents the physical memory of the system and is stored
in the ELF core file format.
With this pseudo-file, and an unstripped
kernel
.RI ( /usr/src/linux/vmlinux )
binary, GDB can be used to
examine the current state of any kernel data structures.
.IP
The total length of the file is the size of physical memory (RAM) plus
4\ KiB.
.TP
.IR /proc/keys " (since Linux 2.6.10)"
See
.BR keyrings (7).
.TP
.IR /proc/key\-users " (since Linux 2.6.10)"
See
.BR keyrings (7).
.TP
.I /proc/kmsg
This file can be used instead of the
.BR syslog (2)
system call to read kernel messages.
A process must have superuser
privileges to read this file, and only one process should read this
file.
This file should not be read if a syslog process is running
which uses the
.BR syslog (2)
system call facility to log kernel messages.
.IP
Information in this file is retrieved with the
.BR dmesg (1)
program.
.TP
.IR /proc/kpagecgroup " (since Linux 4.3)"
.\" commit 80ae2fdceba8313b0433f899bdd9c6c463291a17
This file contains a 64-bit inode number of
the memory cgroup each page is charged to,
indexed by page frame number (see the discussion of
.IR /proc/ pid /pagemap ).
.IP
The
.I /proc/kpagecgroup
file is present only if the
.B CONFIG_MEMCG
kernel configuration option is enabled.
.TP
.IR /proc/kpagecount " (since Linux 2.6.25)"
This file contains a 64-bit count of the number of
times each physical page frame is mapped,
indexed by page frame number (see the discussion of
.IR /proc/ pid /pagemap ).
.IP
The
.I /proc/kpagecount
file is present only if the
.B CONFIG_PROC_PAGE_MONITOR
kernel configuration option is enabled.
.TP
.IR /proc/kpageflags " (since Linux 2.6.25)"
This file contains 64-bit masks corresponding to each physical page frame;
it is indexed by page frame number (see the discussion of
.IR /proc/ pid /pagemap ).
The bits are as follows:
.RS
.IP
.TS
r l l l.
0	-	KPF_LOCKED
1	-	KPF_ERROR
2	-	KPF_REFERENCED
3	-	KPF_UPTODATE
4	-	KPF_DIRTY
5	-	KPF_LRU
6	-	KPF_ACTIVE
7	-	KPF_SLAB
8	-	KPF_WRITEBACK
9	-	KPF_RECLAIM
10	-	KPF_BUDDY
11	-	KPF_MMAP	(since Linux 2.6.31)
12	-	KPF_ANON	(since Linux 2.6.31)
13	-	KPF_SWAPCACHE	(since Linux 2.6.31)
14	-	KPF_SWAPBACKED	(since Linux 2.6.31)
15	-	KPF_COMPOUND_HEAD	(since Linux 2.6.31)
16	-	KPF_COMPOUND_TAIL	(since Linux 2.6.31)
17	-	KPF_HUGE	(since Linux 2.6.31)
18	-	KPF_UNEVICTABLE	(since Linux 2.6.31)
19	-	KPF_HWPOISON	(since Linux 2.6.31)
20	-	KPF_NOPAGE	(since Linux 2.6.31)
21	-	KPF_KSM	(since Linux 2.6.32)
22	-	KPF_THP	(since Linux 3.4)
23	-	KPF_BALLOON	(since Linux 3.18)
.\" KPF_BALLOON: commit 09316c09dde33aae14f34489d9e3d243ec0d5938
24	-	KPF_ZERO_PAGE	(since Linux 4.0)
.\" KPF_ZERO_PAGE: commit 56873f43abdcd574b25105867a990f067747b2f4
25	-	KPF_IDLE	(since Linux 4.3)
.\" KPF_IDLE: commit f074a8f49eb87cde95ac9d040ad5e7ea4f029738
26	-	KPF_PGTABLE	(since Linux 4.18)
.\" KPF_PGTABLE: commit 1d40a5ea01d53251c23c7be541d3f4a656cfc537
.TE
.RE
.IP
For further details on the meanings of these bits,
see the kernel source file
.IR Documentation/admin\-guide/mm/pagemap.rst .
Before Linux 2.6.29,
.\" commit ad3bdefe877afb47480418fdb05ecd42842de65e
.\" commit e07a4b9217d1e97d2f3a62b6b070efdc61212110
.BR KPF_WRITEBACK ,
.BR KPF_RECLAIM ,
.BR KPF_BUDDY ,
and
.B KPF_LOCKED
did not report correctly.
.IP
The
.I /proc/kpageflags
file is present only if the
.B CONFIG_PROC_PAGE_MONITOR
kernel configuration option is enabled.
.TP
.IR /proc/ksyms " (Linux 1.1.23\[en]2.5.47)"
See
.IR /proc/kallsyms .
.TP
.I /proc/loadavg
The first three fields in this file are load average figures
giving the number of jobs in the run queue (state R)
or waiting for disk I/O (state D) averaged over 1, 5, and 15 minutes.
They are the same as the load average numbers given by
.BR uptime (1)
and other programs.
The fourth field consists of two numbers separated by a slash (/).
The first of these is the number of currently runnable kernel
scheduling entities (processes, threads).
The value after the slash is the number of kernel scheduling entities
that currently exist on the system.
The fifth field is the PID of the process that was most
recently created on the system.
.TP
.I /proc/locks
This file shows current file locks
.RB ( flock "(2) and " fcntl (2))
and leases
.RB ( fcntl (2)).
.IP
An example of the content shown in this file is the following:
.IP
.in +4n
.EX
1: POSIX  ADVISORY  READ  5433 08:01:7864448 128 128
2: FLOCK  ADVISORY  WRITE 2001 08:01:7864554 0 EOF
3: FLOCK  ADVISORY  WRITE 1568 00:2f:32388 0 EOF
4: POSIX  ADVISORY  WRITE 699 00:16:28457 0 EOF
5: POSIX  ADVISORY  WRITE 764 00:16:21448 0 0
6: POSIX  ADVISORY  READ  3548 08:01:7867240 1 1
7: POSIX  ADVISORY  READ  3548 08:01:7865567 1826 2335
8: OFDLCK ADVISORY  WRITE \-1 08:01:8713209 128 191
.EE
.in
.IP
The fields shown in each line are as follows:
.RS
.IP [1] 5
The ordinal position of the lock in the list.
.IP [2]
The lock type.
Values that may appear here include:
.RS
.TP
.B FLOCK
This is a BSD file lock created using
.BR flock (2).
.TP
.B OFDLCK
This is an open file description (OFD) lock created using
.BR fcntl (2).
.TP
.B POSIX
This is a POSIX byte-range lock created using
.BR fcntl (2).
.RE
.IP [3]
Among the strings that can appear here are the following:
.RS
.TP
.B ADVISORY
This is an advisory lock.
.TP
.B MANDATORY
This is a mandatory lock.
.RE
.IP [4]
The type of lock.
Values that can appear here are:
.RS
.TP
.B READ
This is a POSIX or OFD read lock, or a BSD shared lock.
.TP
.B WRITE
This is a POSIX or OFD write lock, or a BSD exclusive lock.
.RE
.IP [5]
The PID of the process that owns the lock.
.IP
Because OFD locks are not owned by a single process
(since multiple processes may have file descriptors that
refer to the same open file description),
the value \-1 is displayed in this field for OFD locks.
(Before Linux 4.14,
.\" commit 9d5b86ac13c573795525ecac6ed2db39ab23e2a8
a bug meant that the PID of the process that
initially acquired the lock was displayed instead of the value \-1.)
.IP [6]
Three colon-separated subfields that identify the major and minor device
ID of the device containing the filesystem where the locked file resides,
followed by the inode number of the locked file.
.IP [7]
The byte offset of the first byte of the lock.
For BSD locks, this value is always 0.
.IP [8]
The byte offset of the last byte of the lock.
.B EOF
in this field means that the lock extends to the end of the file.
For BSD locks, the value shown is always
.IR EOF .
.RE
.IP
Since Linux 4.9,
.\" commit d67fd44f697dff293d7cdc29af929241b669affe
the list of locks shown in
.I /proc/locks
is filtered to show just the locks for the processes in the PID
namespace (see
.BR pid_namespaces (7))
for which the
.I /proc
filesystem was mounted.
(In the initial PID namespace,
there is no filtering of the records shown in this file.)
.IP
The
.BR lslocks (8)
command provides a bit more information about each lock.
.TP
.IR /proc/malloc " (only up to and including Linux 2.2)"
.\" It looks like this only ever did something back in 1.0 days
This file is present only if
.B CONFIG_DEBUG_MALLOC
was defined during compilation.
.TP
.I /proc/meminfo
This file reports statistics about memory usage on the system.
It is used by
.BR free (1)
to report the amount of free and used memory (both physical and swap)
on the system as well as the shared memory and buffers used by the
kernel.
Each line of the file consists of a parameter name, followed by a colon,
the value of the parameter, and an option unit of measurement (e.g., "kB").
The list below describes the parameter names and
the format specifier required to read the field value.
Except as noted below,
all of the fields have been present since at least Linux 2.6.0.
Some fields are displayed only if the kernel was configured
with various options; those dependencies are noted in the list.
.RS
.TP
.IR MemTotal " %lu"
Total usable RAM (i.e., physical RAM minus a few reserved
bits and the kernel binary code).
.TP
.IR MemFree " %lu"
The sum of
.IR LowFree + HighFree .
.TP
.IR MemAvailable " %lu (since Linux 3.14)"
An estimate of how much memory is available for starting new
applications, without swapping.
.TP
.IR Buffers " %lu"
Relatively temporary storage for raw disk blocks that
shouldn't get tremendously large (20 MB or so).
.TP
.IR Cached " %lu"
In-memory cache for files read from the disk (the page cache).
Doesn't include
.IR SwapCached .
.TP
.IR SwapCached " %lu"
Memory that once was swapped out, is swapped back in but
still also is in the swap file.
(If memory pressure is high, these pages
don't need to be swapped out again because they are already
in the swap file.
This saves I/O.)
.TP
.IR Active " %lu"
Memory that has been used more recently and usually not
reclaimed unless absolutely necessary.
.TP
.IR Inactive " %lu"
Memory which has been less recently used.
It is more eligible to be reclaimed for other purposes.
.TP
.IR Active(anon) " %lu (since Linux 2.6.28)"
[To be documented.]
.TP
.IR Inactive(anon) " %lu (since Linux 2.6.28)"
[To be documented.]
.TP
.IR Active(file) " %lu (since Linux 2.6.28)"
[To be documented.]
.TP
.IR Inactive(file) " %lu (since Linux 2.6.28)"
[To be documented.]
.TP
.IR Unevictable " %lu (since Linux 2.6.28)"
(From Linux 2.6.28 to Linux 2.6.30,
\fBCONFIG_UNEVICTABLE_LRU\fP was required.)
[To be documented.]
.TP
.IR Mlocked " %lu (since Linux 2.6.28)"
(From Linux 2.6.28 to Linux 2.6.30,
\fBCONFIG_UNEVICTABLE_LRU\fP was required.)
[To be documented.]
.TP
.IR HighTotal " %lu"
(Starting with Linux 2.6.19, \fBCONFIG_HIGHMEM\fP is required.)
Total amount of highmem.
Highmem is all memory above \[ti]860 MB of physical memory.
Highmem areas are for use by user-space programs,
or for the page cache.
The kernel must use tricks to access
this memory, making it slower to access than lowmem.
.TP
.IR HighFree " %lu"
(Starting with Linux 2.6.19, \fBCONFIG_HIGHMEM\fP is required.)
Amount of free highmem.
.TP
.IR LowTotal " %lu"
(Starting with Linux 2.6.19, \fBCONFIG_HIGHMEM\fP is required.)
Total amount of lowmem.
Lowmem is memory which can be used for everything that
highmem can be used for, but it is also available for the
kernel's use for its own data structures.
Among many other things,
it is where everything from
.I Slab
is allocated.
Bad things happen when you're out of lowmem.
.TP
.IR LowFree " %lu"
(Starting with Linux 2.6.19, \fBCONFIG_HIGHMEM\fP is required.)
Amount of free lowmem.
.TP
.IR MmapCopy " %lu (since Linux 2.6.29)"
.RB ( CONFIG_MMU
is required.)
[To be documented.]
.TP
.IR SwapTotal " %lu"
Total amount of swap space available.
.TP
.IR SwapFree " %lu"
Amount of swap space that is currently unused.
.TP
.IR Dirty " %lu"
Memory which is waiting to get written back to the disk.
.TP
.IR Writeback " %lu"
Memory which is actively being written back to the disk.
.TP
.IR AnonPages " %lu (since Linux 2.6.18)"
Non-file backed pages mapped into user-space page tables.
.TP
.IR Mapped " %lu"
Files which have been mapped into memory (with
.BR mmap (2)),
such as libraries.
.TP
.IR Shmem " %lu (since Linux 2.6.32)"
Amount of memory consumed in
.BR tmpfs (5)
filesystems.
.TP
.IR KReclaimable " %lu (since Linux 4.20)"
Kernel allocations that the kernel will attempt to reclaim
under memory pressure.
Includes
.I SReclaimable
(below), and other direct allocations with a shrinker.
.TP
.IR Slab " %lu"
In-kernel data structures cache.
(See
.BR slabinfo (5).)
.TP
.IR SReclaimable " %lu (since Linux 2.6.19)"
Part of
.IR Slab ,
that might be reclaimed, such as caches.
.TP
.IR SUnreclaim " %lu (since Linux 2.6.19)"
Part of
.IR Slab ,
that cannot be reclaimed on memory pressure.
.TP
.IR KernelStack " %lu (since Linux 2.6.32)"
Amount of memory allocated to kernel stacks.
.TP
.IR PageTables " %lu (since Linux 2.6.18)"
Amount of memory dedicated to the lowest level of page tables.
.TP
.IR Quicklists " %lu (since Linux 2.6.27)"
(\fBCONFIG_QUICKLIST\fP is required.)
[To be documented.]
.TP
.IR NFS_Unstable " %lu (since Linux 2.6.18)"
NFS pages sent to the server, but not yet committed to stable storage.
.TP
.IR Bounce " %lu (since Linux 2.6.18)"
Memory used for block device "bounce buffers".
.TP
.IR WritebackTmp " %lu (since Linux 2.6.26)"
Memory used by FUSE for temporary writeback buffers.
.TP
.IR CommitLimit " %lu (since Linux 2.6.10)"
This is the total amount of memory currently available to
be allocated on the system, expressed in kilobytes.
This limit is adhered to
only if strict overcommit accounting is enabled (mode 2 in
.IR /proc/sys/vm/overcommit_memory ).
The limit is calculated according to the formula described under
.IR /proc/sys/vm/overcommit_memory .
For further details, see the kernel source file
.IR Documentation/vm/overcommit\-accounting.rst .
.TP
.IR Committed_AS " %lu"
The amount of memory presently allocated on the system.
The committed memory is a sum of all of the memory which
has been allocated by processes, even if it has not been
"used" by them as of yet.
A process which allocates 1 GB of memory (using
.BR malloc (3)
or similar), but touches only 300 MB of that memory will show up
as using only 300 MB of memory even if it has the address space
allocated for the entire 1 GB.
.IP
This 1 GB is memory which has been "committed" to by the VM
and can be used at any time by the allocating application.
With strict overcommit enabled on the system (mode 2 in
.IR /proc/sys/vm/overcommit_memory ),
allocations which would exceed the
.I CommitLimit
will not be permitted.
This is useful if one needs to guarantee that processes will not
fail due to lack of memory once that memory has been successfully allocated.
.TP
.IR VmallocTotal " %lu"
Total size of vmalloc memory area.
.TP
.IR VmallocUsed " %lu"
Amount of vmalloc area which is used.
Since Linux 4.4,
.\" commit a5ad88ce8c7fae7ddc72ee49a11a75aa837788e0
this field is no longer calculated, and is hard coded as 0.
See
.IR /proc/vmallocinfo .
.TP
.IR VmallocChunk " %lu"
Largest contiguous block of vmalloc area which is free.
Since Linux 4.4,
.\" commit a5ad88ce8c7fae7ddc72ee49a11a75aa837788e0
this field is no longer calculated and is hard coded as 0.
See
.IR /proc/vmallocinfo .
.TP
.IR HardwareCorrupted " %lu (since Linux 2.6.32)"
(\fBCONFIG_MEMORY_FAILURE\fP is required.)
[To be documented.]
.TP
.IR LazyFree " %lu (since Linux 4.12)"
Shows the amount of memory marked by
.BR madvise (2)
.BR MADV_FREE .
.TP
.IR AnonHugePages " %lu (since Linux 2.6.38)"
(\fBCONFIG_TRANSPARENT_HUGEPAGE\fP is required.)
Non-file backed huge pages mapped into user-space page tables.
.TP
.IR ShmemHugePages " %lu (since Linux 4.8)"
(\fBCONFIG_TRANSPARENT_HUGEPAGE\fP is required.)
Memory used by shared memory (shmem) and
.BR tmpfs (5)
allocated with huge pages.
.TP
.IR ShmemPmdMapped " %lu (since Linux 4.8)"
(\fBCONFIG_TRANSPARENT_HUGEPAGE\fP is required.)
Shared memory mapped into user space with huge pages.
.TP
.IR CmaTotal " %lu (since Linux 3.1)"
Total CMA (Contiguous Memory Allocator) pages.
(\fBCONFIG_CMA\fP is required.)
.TP
.IR CmaFree " %lu (since Linux 3.1)"
Free CMA (Contiguous Memory Allocator) pages.
(\fBCONFIG_CMA\fP is required.)
.TP
.IR HugePages_Total " %lu"
(\fBCONFIG_HUGETLB_PAGE\fP is required.)
The size of the pool of huge pages.
.TP
.IR HugePages_Free " %lu"
(\fBCONFIG_HUGETLB_PAGE\fP is required.)
The number of huge pages in the pool that are not yet allocated.
.TP
.IR HugePages_Rsvd " %lu (since Linux 2.6.17)"
(\fBCONFIG_HUGETLB_PAGE\fP is required.)
This is the number of huge pages for
which a commitment to allocate from the pool has been made,
but no allocation has yet been made.
These reserved huge pages
guarantee that an application will be able to allocate a
huge page from the pool of huge pages at fault time.
.TP
.IR HugePages_Surp " %lu (since Linux 2.6.24)"
(\fBCONFIG_HUGETLB_PAGE\fP is required.)
This is the number of huge pages in
the pool above the value in
.IR /proc/sys/vm/nr_hugepages .
The maximum number of surplus huge pages is controlled by
.IR /proc/sys/vm/nr_overcommit_hugepages .
.TP
.IR Hugepagesize " %lu"
(\fBCONFIG_HUGETLB_PAGE\fP is required.)
The size of huge pages.
.TP
.IR DirectMap4k " %lu (since Linux 2.6.27)"
Number of bytes of RAM linearly mapped by kernel in 4 kB pages.
(x86.)
.TP
.IR DirectMap4M " %lu (since Linux 2.6.27)"
Number of bytes of RAM linearly mapped by kernel in 4 MB pages.
(x86 with
.B CONFIG_X86_64
or
.B CONFIG_X86_PAE
enabled.)
.TP
.IR DirectMap2M " %lu (since Linux 2.6.27)"
Number of bytes of RAM linearly mapped by kernel in 2 MB pages.
(x86 with neither
.B CONFIG_X86_64
nor
.B CONFIG_X86_PAE
enabled.)
.TP
.IR DirectMap1G " %lu (since Linux 2.6.27)"
(x86 with
.B CONFIG_X86_64
and
.B CONFIG_X86_DIRECT_GBPAGES
enabled.)
.RE
.TP
.I /proc/modules
A text list of the modules that have been loaded by the system.
See also
.BR lsmod (8).
.TP
.I /proc/mtrr
Memory Type Range Registers.
See the Linux kernel source file
.I Documentation/x86/mtrr.rst
(or
.I Documentation/x86/mtrr.txt
.\" commit 7225e75144b9718cbbe1820d9c011c809d5773fd
before Linux 5.2, or
.I Documentation/mtrr.txt
before Linux 2.6.28)
for details.
.TP
.I /proc/partitions
Contains the major and minor numbers of each partition as well as the number
of 1024-byte blocks and the partition name.
.TP
.I /proc/pci
This is a listing of all PCI devices found during kernel initialization
and their configuration.
.IP
This file has been deprecated in favor of a new
.I /proc
interface for PCI
.RI ( /proc/bus/pci ).
It became optional in Linux 2.2 (available with
.B CONFIG_PCI_OLD_PROC
set at kernel compilation).
It became once more nonoptionally enabled in Linux 2.4.
Next, it was deprecated in Linux 2.6 (still available with
.B CONFIG_PCI_LEGACY_PROC
set), and finally removed altogether since Linux 2.6.17.
.\" FIXME Document /proc/sched_debug (since Linux 2.6.23)
.\" See also /proc/[pid]/sched
.TP
.IR /proc/profile " (since Linux 2.4)"
This file is present only if the kernel was booted with the
.I profile=1
command-line option.
It exposes kernel profiling information in a binary format for use by
.BR readprofile (1).
Writing (e.g., an empty string) to this file resets the profiling counters;
on some architectures,
writing a binary integer "profiling multiplier" of size
.I sizeof(int)
sets the profiling interrupt frequency.
.TP
.I /proc/scsi
A directory with the
.I scsi
mid-level pseudo-file and various SCSI low-level
driver directories,
which contain a file for each SCSI host in this system, all of
which give the status of some part of the SCSI IO subsystem.
These files contain ASCII structures and are, therefore, readable with
.BR cat (1).
.IP
You can also write to some of the files to reconfigure the subsystem or
switch certain features on or off.
.TP
.I /proc/scsi/scsi
This is a listing of all SCSI devices known to the kernel.
The listing is similar to the one seen during bootup.
scsi currently supports only the \fIadd\-single\-device\fP command which
allows root to add a hotplugged device to the list of known devices.
.IP
The command
.IP
.in +4n
.EX
echo \[aq]scsi add\-single\-device 1 0 5 0\[aq] > /proc/scsi/scsi
.EE
.in
.IP
will cause
host scsi1 to scan on SCSI channel 0 for a device on ID 5 LUN 0.
If there
is already a device known on this address or the address is invalid, an
error will be returned.
.TP
.IR /proc/scsi/ drivername
\fIdrivername\fP can currently be NCR53c7xx, aha152x, aha1542, aha1740,
aic7xxx, buslogic, eata_dma, eata_pio, fdomain, in2000, pas16, qlogic,
scsi_debug, seagate, t128, u15\-24f, ultrastore, or wd7000.
These directories show up for all drivers that registered at least one
SCSI HBA.
Every directory contains one file per registered host.
Every host-file is named after the number the host was assigned during
initialization.
.IP
Reading these files will usually show driver and host configuration,
statistics, and so on.
.IP
Writing to these files allows different things on different hosts.
For example, with the \fIlatency\fP and \fInolatency\fP commands,
root can switch on and off command latency measurement code in the
eata_dma driver.
With the \fIlockup\fP and \fIunlock\fP commands,
root can control bus lockups simulated by the scsi_debug driver.
.TP
.I /proc/self
This directory refers to the process accessing the
.I /proc
filesystem,
and is identical to the
.I /proc
directory named by the process ID of the same process.
.TP
.I /proc/slabinfo
Information about kernel caches.
See
.BR slabinfo (5)
for details.
.TP
.I /proc/stat
kernel/system statistics.
Varies with architecture.
Common
entries include:
.RS
.TP
.I cpu  10132153 290696 3084719 46828483 16683 0 25195 0 175628 0
.TQ
.I cpu0 1393280 32966 572056 13343292 6130 0 17875 0 23933 0
The amount of time, measured in units of
USER_HZ (1/100ths of a second on most architectures, use
.I sysconf(_SC_CLK_TCK)
to obtain the right value),
.\" 1024 on Alpha and ia64
that the system ("cpu" line) or the specific CPU ("cpu\fIN\fR" line)
spent in various states:
.RS
.TP
.I user
(1) Time spent in user mode.
.TP
.I nice
(2) Time spent in user mode with low priority (nice).
.TP
.I system
(3) Time spent in system mode.
.TP
.I idle
(4) Time spent in the idle task.
.\" FIXME . Actually, the following info about the /proc/stat 'cpu' field
.\"       does not seem to be quite right (at least in Linux 2.6.12 or Linux 3.6):
.\"       the idle time in /proc/uptime does not quite match this value
This value should be USER_HZ times the
second entry in the
.I /proc/uptime
pseudo-file.
.TP
.IR iowait " (since Linux 2.5.41)"
(5) Time waiting for I/O to complete.
This value is not reliable, for the following reasons:
.\" See kernel commit 9c240d757658a3ae9968dd309e674c61f07c7f48
.RS
.IP \[bu] 3
The CPU will not wait for I/O to complete;
iowait is the time that a task is waiting for I/O to complete.
When a CPU goes into idle state for outstanding task I/O,
another task will be scheduled on this CPU.
.IP \[bu]
On a multi-core CPU,
the task waiting for I/O to complete is not running on any CPU,
so the iowait of each CPU is difficult to calculate.
.IP \[bu]
The value in this field may
.I decrease
in certain conditions.
.RE
.TP
.IR irq " (since Linux 2.6.0)"
.\" Precisely: Linux 2.6.0-test4
(6) Time servicing interrupts.
.TP
.IR softirq " (since Linux 2.6.0)"
.\" Precisely: Linux 2.6.0-test4
(7) Time servicing softirqs.
.TP
.IR steal " (since Linux 2.6.11)"
(8) Stolen time, which is the time spent in other operating systems when
running in a virtualized environment
.TP
.IR guest " (since Linux 2.6.24)"
(9) Time spent running a virtual CPU for guest
operating systems under the control of the Linux kernel.
.\" See Changelog entry for 5e84cfde51cf303d368fcb48f22059f37b3872de
.TP
.IR guest_nice " (since Linux 2.6.33)"
.\" commit ce0e7b28fb75cb003cfc8d0238613aaf1c55e797
(10) Time spent running a niced guest (virtual CPU for guest
operating systems under the control of the Linux kernel).
.RE
.TP
\fIpage 5741 1808\fP
The number of pages the system paged in and the number that were paged
out (from disk).
.TP
\fIswap 1 0\fP
The number of swap pages that have been brought in and out.
.TP
.\" FIXME . The following is not the full picture for the 'intr' of
.\"       /proc/stat on 2.6:
\fIintr 1462898\fP
This line shows counts of interrupts serviced since boot time,
for each of the possible system interrupts.
The first column is the total of all interrupts serviced
including unnumbered architecture specific interrupts;
each subsequent column is the total for that particular numbered interrupt.
Unnumbered interrupts are not shown, only summed into the total.
.TP
\fIdisk_io: (2,0):(31,30,5764,1,2) (3,0):\fP...
(major,disk_idx):(noinfo, read_io_ops, blks_read, write_io_ops, blks_written)
.br
(Linux 2.4 only)
.TP
\fIctxt 115315\fP
The number of context switches that the system underwent.
.TP
\fIbtime 769041601\fP
boot time, in seconds since the Epoch, 1970-01-01 00:00:00 +0000 (UTC).
.TP
\fIprocesses 86031\fP
Number of forks since boot.
.TP
\fIprocs_running 6\fP
Number of processes in runnable state.
(Linux 2.5.45 onward.)
.TP
\fIprocs_blocked 2\fP
Number of processes blocked waiting for I/O to complete.
(Linux 2.5.45 onward.)
.TP
.I softirq 229245889 94 60001584 13619 5175704 2471304 28 51212741 59130143 0 51240672
.\" commit d3d64df21d3d0de675a0d3ffa7c10514f3644b30
This line shows the number of softirq for all CPUs.
The first column is the total of all softirqs and
each subsequent column is the total for particular softirq.
(Linux 2.6.31 onward.)
.RE
.TP
.I /proc/swaps
Swap areas in use.
See also
.BR swapon (8).
.TP
.I /proc/sys
This directory (present since Linux 1.3.57) contains a number of files
and subdirectories corresponding to kernel variables.
These variables can be read and in some cases modified using
the \fI/proc\fP filesystem, and the (deprecated)
.BR sysctl (2)
system call.
.IP
String values may be terminated by either \[aq]\e0\[aq] or \[aq]\en\[aq].
.IP
Integer and long values may be written either in decimal or in
hexadecimal notation (e.g., 0x3FFF).
When writing multiple integer or long values, these may be separated
by any of the following whitespace characters:
\[aq]\ \[aq], \[aq]\et\[aq], or \[aq]\en\[aq].
Using other separators leads to the error
.BR EINVAL .
.TP
.IR /proc/sys/abi " (since Linux 2.4.10)"
This directory may contain files with application binary information.
.\" On some systems, it is not present.
See the Linux kernel source file
.I Documentation/sysctl/abi.rst
(or
.I Documentation/sysctl/abi.txt
before Linux 5.3)
for more information.
.TP
.I /proc/sys/debug
This directory may be empty.
.TP
.I /proc/sys/dev
This directory contains device-specific information (e.g.,
.IR dev/cdrom/info ).
On
some systems, it may be empty.
.TP
.I /proc/sys/fs
This directory contains the files and subdirectories for kernel variables
related to filesystems.
.TP
.IR /proc/sys/fs/aio\-max\-nr " and " /proc/sys/fs/aio\-nr " (since Linux 2.6.4)"
.I aio\-nr
is the running total of the number of events specified by
.BR io_setup (2)
calls for all currently active AIO contexts.
If
.I aio\-nr
reaches
.IR aio\-max\-nr ,
then
.BR io_setup (2)
will fail with the error
.BR EAGAIN .
Raising
.I aio\-max\-nr
does not result in the preallocation or resizing
of any kernel data structures.
.TP
.I /proc/sys/fs/binfmt_misc
Documentation for files in this directory can be found
in the Linux kernel source in the file
.I Documentation/admin\-guide/binfmt\-misc.rst
(or in
.I Documentation/binfmt_misc.txt
on older kernels).
.TP
.IR /proc/sys/fs/dentry\-state " (since Linux 2.2)"
This file contains information about the status of the
directory cache (dcache).
The file contains six numbers,
.IR nr_dentry ,
.IR nr_unused ,
.I age_limit
(age in seconds),
.I want_pages
(pages requested by system) and two dummy values.
.RS
.IP \[bu] 3
.I nr_dentry
is the number of allocated dentries (dcache entries).
This field is unused in Linux 2.2.
.IP \[bu]
.I nr_unused
is the number of unused dentries.
.IP \[bu]
.I age_limit
.\" looks like this is unused in Linux 2.2 to Linux 2.6
is the age in seconds after which dcache entries
can be reclaimed when memory is short.
.IP \[bu]
.I want_pages
.\" looks like this is unused in Linux 2.2 to Linux 2.6
is nonzero when the kernel has called shrink_dcache_pages() and the
dcache isn't pruned yet.
.RE
.TP
.I /proc/sys/fs/dir\-notify\-enable
This file can be used to disable or enable the
.I dnotify
interface described in
.BR fcntl (2)
on a system-wide basis.
A value of 0 in this file disables the interface,
and a value of 1 enables it.
.TP
.I /proc/sys/fs/dquot\-max
This file shows the maximum number of cached disk quota entries.
On some (2.4) systems, it is not present.
If the number of free cached disk quota entries is very low and
you have some awesome number of simultaneous system users,
you might want to raise the limit.
.TP
.I /proc/sys/fs/dquot\-nr
This file shows the number of allocated disk quota
entries and the number of free disk quota entries.
.TP
.IR /proc/sys/fs/epoll " (since Linux 2.6.28)"
This directory contains the file
.IR max_user_watches ,
which can be used to limit the amount of kernel memory consumed by the
.I epoll
interface.
For further details, see