.\" to see what information could be imported from that file
.\" into this file.
.\"
-.TH PROC 5 2017-09-15 "Linux" "Linux Programmer's Manual"
+.TH PROC 5 2019-03-06 "Linux" "Linux Programmer's Manual"
.SH NAME
proc \- process information pseudo-filesystem
.SH DESCRIPTION
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
+.I /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
+.I /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
+.I /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
+.I /proc/[pid]
+directory.
+.TP
+.I /proc/thread-self
+When a thread accesses this magic symbolic link,
+it resolves to the process's own
+.I /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 describes many of the files and directories under the
+The following list provides details of many of the files and directories
+under the
.I /proc
hierarchy.
.TP
See
.BR sched (7).
.TP
-.IR /proc/[pid]/auxv " (since 2.6.0-test7)"
+.IR /proc/[pid]/auxv " (since 2.6.0)"
+.\" Precisely: Linux 2.6.0-test7
This contains the contents of the ELF interpreter information passed
to the process at exec time.
The format is one \fIunsigned long\fP ID
In the latter case, there is nothing in this file:
that is, a read on this file will return 0 characters.
The command-line arguments appear in this file as a set of
-strings separated by null bytes (\(aq\\0\(aq),
+strings separated by null bytes (\(aq\e0\(aq),
with a further null byte after the last string.
.TP
.IR /proc/[pid]/comm " (since Linux 2.6.33)"
This file contains the initial environment that was set
when the currently executing program was started via
.BR execve (2).
-The entries are separated by null bytes (\(aq\\0\(aq),
+The entries are separated by null bytes (\(aq\e0\(aq),
and there may be a null byte at the end.
Thus, to print out the environment of process 1, you would do:
.IP
.in +4n
.EX
-.RB "$" " strings /proc/1/environ"
+.RB "$" " cat /proc/1/environ | tr \(aq\e000\(aq \(aq\en\(aq"
.EE
.in
.IP
.IP
For details on these fields, see
.BR fanotify_mark (2).
+.IP
+For timerfd file descriptors (see
+.BR timerfd (2)),
+we see (since Linux 3.17)
+.\" commit af9c4957cf212ad9cf0bee34c95cb11de5426e85
+the following fields:
+.IP
+.in +4n
+.EX
+pos: 0
+flags: 02004002
+mnt_id: 13
+clockid: 0
+ticks: 0
+settime flags: 03
+it_value: (7695568592, 640020877)
+it_interval: (0, 0)
+.EE
+.in
+.RS
+.TP
+.I clockid
+This is the numeric value of the clock ID
+(corresponding to one of the
+.B CLOCK_*
+constants defined via
+.IR <time.h> )
+that is used to mark the progress of the timer (in this example, 0 is
+.BR CLOCK_REALTIME ).
+.TP
+.I ticks
+This is the number of timer expirations that have occurred,
+(i.e., the value that
+.BR read (2)
+on it would return).
+.TP
+.I settime flags
+This field lists the flags with which the timerfd was last armed (see
+.BR timerfd_settime (2)),
+in octal
+(in this example, both
+.B TFD_TIMER_ABSTIME
+and
+.B TFD_TIMER_CANCEL_ON_SET
+are set).
+.TP
+.I it_value
+This field contains the amount of time until the timer will next expire,
+expressed in seconds and nanoseconds.
+This is always expressed as a relative value,
+regardless of whether the timer was created using the
+.B TFD_TIMER_ABSTIME
+flag.
+.TP
+.I it_interval
+This field contains the interval of the timer,
+in seconds and nanoseconds.
+(The
+.I it_value
+and
+.I it_interval
+fields contain the values that
+.BR timerfd_gettime (2)
+on this file descriptor would return.)
+.RE
.TP
.IR /proc/[pid]/gid_map " (since Linux 3.5)"
See
.IR [stack]
The initial process's (also known as the main thread's) stack.
.TP
-.IR [stack:<tid>] " (since Linux 3.4)"
-.\" commit b76437579d1344b612cf1851ae610c636cec7db0
+.IR [stack:<tid>] " (from Linux 3.4 to 4.4)"
+.\" commit b76437579d1344b612cf1851ae610c636cec7db0 (added)
+.\" commit 65376df582174ffcec9e6471bf5b0dd79ba05e4a (removed)
A thread's stack (where the
.IR <tid>
is a thread ID).
It corresponds to the
.IR /proc/[pid]/task/[tid]/
path.
+This field was removed in Linux 4.5, since providing this information
+for a process with large numbers of threads is expensive.
.TP
.IR [vdso]
The virtual dynamically linked shared object.
.BR strace (1),
or similar.
.IP
+.I pathname
+is shown unescaped except for newline characters, which are replaced
+with an octal escape sequence.
+As a result, it is not possible to determine whether the original
+pathname contained a newline character or the literal
+.I \ee012
+character sequence.
+.IP
+If the mapping is file-backed and the file has been deleted, the string
+" (deleted)" is appended to the pathname.
+Note that this is ambiguous too.
+.IP
Under Linux 2.0, there is no field giving pathname.
.TP
.I /proc/[pid]/mem
to the process's root directory.
.TP
(6)
-mount options: per-mount options.
+mount options: per-mount options (see
+.BR mount (2)).
.TP
(7)
optional fields: zero or more fields of the form "tag[:value]"; see below.
mount source: filesystem-specific information or "none".
.TP
(11)
-super options: per-superblock options.
+super options: per-superblock options (see
+.BR mount (2)).
.RE
.IP
Currently, the possible optional fields are
55 (since Linux 3.11)
PTE is soft-dirty
(see the kernel source file
-.IR Documentation/vm/soft-dirty.txt ).
+.IR Documentation/admin-guide/mm/soft-dirty.rst ).
.TP
54\(en0
If the page is present in RAM (bit 63), then these bits
VmPMD: 12 kB
VmSwap: 0 kB
HugetlbPages: 0 kB # 4.4
+CoreDumping: 0 # 4.15
Threads: 1
SigQ: 0/3067
SigPnd: 0000000000000000
CapAmb: 0000000000000000
NoNewPrivs: 0
Seccomp: 0
+Speculation_Store_Bypass: vulnerable
Cpus_allowed: 00000001
Cpus_allowed_list: 0
Mems_allowed: 1
.IR Groups :
Supplementary group list.
.IP *
-.I NStgid :
+.IR NStgid :
Thread group ID (i.e., PID) in each of the PID namespaces of which
.I [pid]
is a member.
.\" commit e4bc33245124db69b74a6d853ac76c2976f472d5
(Since Linux 4.1.)
.IP *
-.IR NSpid:
+.IR NSpid :
Thread ID in each of the PID namespaces of which
.I [pid]
is a member.
.IP *
.IR VmPMD :
.\" commit dc6c9a35b66b520cf67e05d8ca60ebecad3b0479
-Size of second-level page tables (since Linux 4.0).
+Size of second-level page tables (added in Linux 4.0; removed in Linux 4.15).
.IP *
.IR VmSwap :
.\" commit b084d4353ff99d824d3bc5a5c2c22c70b1fba722
shmem swap usage is not included (since Linux 2.6.34).
.IP *
.IR HugetlbPages :
-Size of hugetlb memory portions.
+Size of hugetlb memory portions
.\" commit 5d317b2b6536592a9b51fe65faed43d65ca9158e
(since Linux 4.4).
.IP *
+.IR CoreDumping :
+Contains the value 1 if the process is currently dumping core,
+and 0 if it is not
+.\" commit c643401218be0f4ab3522e0c0a63016596d6e9ca
+(since Linux 4.15).
+This information can be used by a monitoring process to avoid killing
+a process that is currently dumping core,
+which could result in a corrupted core dump file.
+.IP *
.IR Threads :
Number of threads in process containing this thread.
.IP *
.BR CONFIG_SECCOMP
kernel configuration option enabled.
.IP *
+.IR Speculation_Store_Bypass :
+.\" commit fae1fa0fc6cca8beee3ab8ed71d54f9a78fa3f64
+Speculation flaw mitigation state
+(since Linux 4.17, see
+.BR prctl (2)).
+.IP *
.IR Cpus_allowed :
Mask of CPUs on which this process may run
(since Linux 2.6.24, see
check; see
.BR ptrace (2).
.TP
-.IR /proc/[pid]/task " (since Linux 2.6.0-test6)"
+.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
.I /proc/[pid]
or they might not exist in
.I /proc/[pid]
at all.
+.IP
.\" The following was still true as at kernel 2.6.13
In a multithreaded process, the contents of the
.I /proc/[pid]/task
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
+.I /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
.IP
For further details on the meanings of these bits,
see the kernel source file
-.IR Documentation/vm/pagemap.txt .
+.IR Documentation/admin-guide/mm/pagemap.rst .
Before kernel 2.6.29,
.\" commit ad3bdefe877afb47480418fdb05ecd42842de65e
.\" commit e07a4b9217d1e97d2f3a62b6b070efdc61212110
.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
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 .
+.IR Documentation/vm/overcommit-accounting.rst .
.TP
.IR Committed_AS " %lu"
The amount of memory presently allocated on the system.
.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.
in certain conditions.
.RE
.TP
-.IR irq " (since Linux 2.6.0-test4)"
+.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-test4)"
+.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)"
.BR sysctl (2)
system call.
.IP
-String values may be terminated by either \(aq\\0\(aq or \(aq\\n\(aq.
+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\\t\(aq, or \(aq\\n\(aq.
+\(aq\ \(aq, \(aq\et\(aq, or \(aq\en\(aq.
Using other separators leads to the error
.BR EINVAL .
.TP
CommitLimit = overcommit_kbytes + total_swap
.IP
See also the description of
-.IR /proc/sys/vm/admiin_reserve_kbytes
+.IR /proc/sys/vm/admin_reserve_kbytes
and
.IR /proc/sys/vm/user_reserve_kbytes .
.TP
tty drivers and line disciplines.
.TP
.I /proc/uptime
-This file contains two numbers: the uptime of the system (seconds),
-and the amount of time spent in idle process (seconds).
+This file contains two numbers (values in seconds): the uptime of the
+system (including time spent in suspend) and the amount of time spent
+in the idle process.
.TP
.I /proc/version
This string identifies the kernel version that is currently running.
.IR compact_stall " (since Linux 2.6.35)"
.\" commit 56de7263fcf3eb10c8dcdf8d59a9cec831795f3f
See the kernel source file
-.IR Documentation/vm/transhuge.txt .
+.IR Documentation/admin-guide/mm/transhuge.rst .
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.IR compact_fail " (since Linux 2.6.35)"
.\" commit 56de7263fcf3eb10c8dcdf8d59a9cec831795f3f
See the kernel source file
-.IR Documentation/vm/transhuge.txt .
+.IR Documentation/admin-guide/mm/transhuge.rst .
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.IR compact_success " (since Linux 2.6.35)"
.\" commit 56de7263fcf3eb10c8dcdf8d59a9cec831795f3f
See the kernel source file
-.IR Documentation/vm/transhuge.txt .
+.IR Documentation/admin-guide/mm/transhuge.rst .
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.IR thp_fault_alloc " (since Linux 2.6.39)"
.\" commit 81ab4201fb7d91d6b0cd9ad5b4b16776e4bed145
See the kernel source file
-.IR Documentation/vm/transhuge.txt .
+.IR Documentation/admin-guide/mm/transhuge.rst .
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.IR thp_fault_fallback " (since Linux 2.6.39)"
.\" commit 81ab4201fb7d91d6b0cd9ad5b4b16776e4bed145
See the kernel source file
-.IR Documentation/vm/transhuge.txt .
+.IR Documentation/admin-guide/mm/transhuge.rst .
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.IR thp_collapse_alloc " (since Linux 2.6.39)"
.\" commit 81ab4201fb7d91d6b0cd9ad5b4b16776e4bed145
See the kernel source file
-.IR Documentation/vm/transhuge.txt .
+.IR Documentation/admin-guide/mm/transhuge.rst .
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.IR thp_collapse_alloc_failed " (since Linux 2.6.39)"
.\" commit 81ab4201fb7d91d6b0cd9ad5b4b16776e4bed145
See the kernel source file
-.IR Documentation/vm/transhuge.txt .
+.IR Documentation/admin-guide/mm/transhuge.rst .
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.IR thp_split " (since Linux 2.6.39)"
.\" commit 81ab4201fb7d91d6b0cd9ad5b4b16776e4bed145
See the kernel source file
-.IR Documentation/vm/transhuge.txt .
+.IR Documentation/admin-guide/mm/transhuge.rst .
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.IR thp_zero_page_alloc " (since Linux 3.8)"
.\" commit d8a8e1f0da3d29d7268b3300c96a059d63901b76
See the kernel source file
-.IR Documentation/vm/transhuge.txt .
+.IR Documentation/admin-guide/mm/transhuge.rst .
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
.IR thp_zero_page_alloc_failed " (since Linux 3.8)"
.\" commit d8a8e1f0da3d29d7268b3300c96a059d63901b76
See the kernel source file
-.IR Documentation/vm/transhuge.txt .
+.IR Documentation/admin-guide/mm/transhuge.rst .
.\" Present only if the kernel was configured with
.\" .BR CONFIG_VM_EVENT_COUNTERS
.\" and
This is useful for analyzing virtual memory behavior.
.\" FIXME more should be said about /proc/zoneinfo
.SH NOTES
-Many strings (i.e., the environment and command line) are in
-the internal format, with subfields terminated by null bytes (\(aq\\0\(aq),
-so you
-may find that things are more readable if you use \fIod \-c\fP or \fItr
-"\\000" "\\n"\fP to read them.
-Alternatively, \fIecho \`cat <file>\`\fP works well.
+Many files contain strings (e.g., the environment and command line)
+that are in the internal format,
+with subfields terminated by null bytes (\(aq\e0\(aq).
+When inspecting such files, you may find that the results are more readable
+if you use a command of the following form to display them:
+.PP
+.in +4n
+.EX
+.RB "$" " cat \fIfile\fP | tr \(aq\e000\(aq \(aq\en\(aq"
+.EE
+.in
.PP
This manual page is incomplete, possibly inaccurate, and is the kind
of thing that needs to be updated very often.
.BR dmesg (1),
.BR find (1),
.BR free (1),
+.BR htop (1),
.BR init (1),
.BR ps (1),
+.BR pstree (1),
.BR tr (1),
.BR uptime (1),
.BR chroot (2),
.BR sysctl (8)
.PP
The Linux kernel source files:
-.IR Documentation/filesystems/proc.txt
+.IR Documentation/filesystems/proc.txt ,
.IR Documentation/sysctl/fs.txt ,
.IR Documentation/sysctl/kernel.txt ,
.IR Documentation/sysctl/net.txt ,
projects / thirdparty / man-pages.git / blobdiff