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
.I /proc/[pid]
There is a numerical subdirectory for each running process; the
subdirectory is named by the process ID.
-.IP
Each
.I /proc/[pid]
-subdirectory contains the
-pseudo-files and directories described below.
-These files are normally owned by the effective user and
+subdirectory contains the pseudo-files and directories described below.
+.IP
+The files inside each
+.I /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
.IR root:root
if the process's "dumpable" attribute is set to a value other than 1.
-This attribute may change for the following reasons:
+.IP
+Before Linux 4.11,
+.\" commit 68eb94f16227336a5773b83ecfa8290f1d6b78ce
+.IR 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
+.I /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 * 3
The attribute was explicitly set via the
.IP
Resetting the "dumpable" attribute to 1 reverts the ownership of the
.IR /proc/[pid]/*
-files to the process's real UID and real GID.
+files to the process's effective UID and GID.
.TP
.I /proc/[pid]/attr
.\" https://lwn.net/Articles/28222/
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
.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 \\\012
+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
parent ID: the ID of the parent mount
(or of self for the root of this mount namespace's mount tree).
.IP
+If a new mount is stacked on top of a previous existing mount
+(so that it hides the existing mount) at pathname P,
+then the parent of the new mount is the previous mount at that location.
+Thus, when looking at all the mounts stacked at a particular location,
+the top-most mount is the one that is not the parent
+of any other mount at the same location.
+(Note, however, that this top-most mount will be accessible only if
+the longest path subprefix of P that is a mount point
+is not itself hidden by a stacked mount.)
+.IP
If the parent mount point lies outside the process's root directory (see
.BR chroot (2)),
the ID shown here won't have a corresponding record in
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
or
.IR /proc/[pid]/oom_adj
will change the other with its scaled value.
+.IP
+The
+.BR choom (1)
+program provides a command-line interface for adjusting the
+.I oom_score_adj
+value of a running process or a newly executed command.
.TP
.IR /proc/[pid]/pagemap " (since Linux 2.6.25)"
This file shows the mapping of each of the process's virtual pages
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.
The leftmost entry shows the value with respect to the PID namespace
-of the reading process,
+of the process that mounted this procfs (or the root namespace
+if mounted by the kernel),
followed by the value in successively nested inner namespaces.
.\" 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 VmLck :
Locked memory size (see
-.BR mlock (3)).
+.BR mlock (2)).
.IP *
.IR VmPin :
Pinned memory size
.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
for which the
.I /proc
filesystem was mounted.
-(In the the initial PID namespace,
+(In the initial PID namespace,
there is no filtering of the records shown in this file.)
.IP
The
.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.
the internal state of the socket.
.TP
.IR Path :
-the bound path (if any) of the socket.
+the bound pathname (if any) of the socket.
Sockets in the abstract namespace are included in the list,
and are shown with a
.I Path
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)"
.TP
.I /proc/sys/kernel/hotplug
This file
-contains the path for the hotplug policy agent.
+contains the pathname for the hotplug policy agent.
The default value in this file is
.IR /sbin/hotplug .
.TP
Enabled if nonzero.
.TP
.I /proc/sys/kernel/modprobe
-This file contains the path for the kernel module loader.
+This file contains the pathname for the kernel module loader.
The default value is
.IR /sbin/modprobe .
The file is present only if the kernel is built with the
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
If enabled in the kernel
.RB ( CONFIG_TIMER_STATS ),
but not used,
-it has almost zero runtime overhead and a relatively small
+it has almost zero run-time overhead and a relatively small
data-structure overhead.
-Even if collection is enabled at runtime, overhead is low:
+Even if collection is enabled at run time, overhead is low:
all the locking is per-CPU and lookup is hashed.
.IP
The
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\\0\(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),
projects / thirdparty / man-pages.git / blobdiff