c9253e931d
- update for getrlimit(2) manpage; - support for setting RLIMIT_SWAP in login class; - addition to the limits(1) and sh and csh limit-setting builtins; - tuning(7) documentation on the sysctls controlling overcommit. In collaboration with: pho Reviewed by: alc Approved by: re (kensmith)
204 lines
6.2 KiB
Groff
204 lines
6.2 KiB
Groff
.\" Copyright (c) 1980, 1991, 1993
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.\" The Regents of the University of California. All rights reserved.
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.\" SUCH DAMAGE.
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.\"
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.\" @(#)getrlimit.2 8.1 (Berkeley) 6/4/93
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.\" $FreeBSD$
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.\"
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.Dd August 20, 2008
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.Dt GETRLIMIT 2
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.Os
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.Sh NAME
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.Nm getrlimit ,
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.Nm setrlimit
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.Nd control maximum system resource consumption
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.Sh LIBRARY
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.Lb libc
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.Sh SYNOPSIS
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.In sys/types.h
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.In sys/time.h
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.In sys/resource.h
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.Ft int
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.Fn getrlimit "int resource" "struct rlimit *rlp"
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.Ft int
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.Fn setrlimit "int resource" "const struct rlimit *rlp"
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.Sh DESCRIPTION
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Limits on the consumption of system resources by the current process
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and each process it creates may be obtained with the
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.Fn getrlimit
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system call, and set with the
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.Fn setrlimit
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system call.
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.Pp
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The
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.Fa resource
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argument is one of the following:
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.Bl -tag -width RLIMIT_FSIZEAA
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.It Dv RLIMIT_AS
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The maximum amount (in bytes) of virtual memory the process is
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allowed to map.
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.It Dv RLIMIT_CORE
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The largest size (in bytes)
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.Xr core 5
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file that may be created.
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.It Dv RLIMIT_CPU
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The maximum amount of cpu time (in seconds) to be used by
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each process.
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.It Dv RLIMIT_DATA
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The maximum size (in bytes) of the data segment for a process;
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this defines how far a program may extend its break with the
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.Xr sbrk 2
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function.
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.It Dv RLIMIT_FSIZE
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The largest size (in bytes) file that may be created.
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.It Dv RLIMIT_MEMLOCK
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The maximum size (in bytes) which a process may lock into memory
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using the
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.Xr mlock 2
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system call.
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.It Dv RLIMIT_NOFILE
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The maximum number of open files for this process.
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.It Dv RLIMIT_NPROC
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The maximum number of simultaneous processes for this user id.
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.It Dv RLIMIT_RSS
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The maximum size (in bytes) to which a process's resident set size may
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grow.
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This imposes a limit on the amount of physical memory to be given to
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a process; if memory is tight, the system will prefer to take memory
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from processes that are exceeding their declared resident set size.
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.It Dv RLIMIT_SBSIZE
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The maximum size (in bytes) of socket buffer usage for this user.
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This limits the amount of network memory, and hence the amount of
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mbufs, that this user may hold at any time.
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.It Dv RLIMIT_STACK
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The maximum size (in bytes) of the stack segment for a process;
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this defines how far a program's stack segment may be extended.
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Stack extension is performed automatically by the system.
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.It Dv RLIMIT_SWAP
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The maximum size (in bytes) of the swap space that may be reserved or
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used by all of this user id's processes.
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This limit is enforced only if bit 1 of the
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.Va vm.overcommit
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sysctl is set.
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Please see
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.Xr tuning 7
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for a complete description of this sysctl.
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.It Dv RLIMIT_NPTS
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The maximum number of pseudo-terminals created by this user id.
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.El
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.Pp
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A resource limit is specified as a soft limit and a hard limit.
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When a
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soft limit is exceeded a process may receive a signal (for example, if
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the cpu time or file size is exceeded), but it will be allowed to
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continue execution until it reaches the hard limit (or modifies
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its resource limit).
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The
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.Vt rlimit
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structure is used to specify the hard and soft limits on a resource,
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.Bd -literal -offset indent
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struct rlimit {
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rlim_t rlim_cur; /* current (soft) limit */
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rlim_t rlim_max; /* maximum value for rlim_cur */
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};
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.Ed
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.Pp
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Only the super-user may raise the maximum limits.
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Other users
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may only alter
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.Fa rlim_cur
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within the range from 0 to
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.Fa rlim_max
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or (irreversibly) lower
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.Fa rlim_max .
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.Pp
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An
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.Dq infinite
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value for a limit is defined as
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.Dv RLIM_INFINITY .
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.Pp
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Because this information is stored in the per-process information,
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this system call must be executed directly by the shell if it
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is to affect all future processes created by the shell;
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.Ic limit
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is thus a built-in command to
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.Xr csh 1 .
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.Pp
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The system refuses to extend the data or stack space when the limits
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would be exceeded in the normal way: a
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.Xr brk 2
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function fails if the data space limit is reached.
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When the stack limit is reached, the process receives
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a segmentation fault
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.Pq Dv SIGSEGV ;
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if this signal is not
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caught by a handler using the signal stack, this signal
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will kill the process.
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.Pp
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A file I/O operation that would create a file larger that the process'
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soft limit will cause the write to fail and a signal
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.Dv SIGXFSZ
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to be
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generated; this normally terminates the process, but may be caught.
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When
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the soft cpu time limit is exceeded, a signal
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.Dv SIGXCPU
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is sent to the
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offending process.
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.Sh RETURN VALUES
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.Rv -std
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.Sh ERRORS
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The
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.Fn getrlimit
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and
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.Fn setrlimit
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system calls
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will fail if:
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.Bl -tag -width Er
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.It Bq Er EFAULT
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The address specified for
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.Fa rlp
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is invalid.
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.It Bq Er EPERM
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The limit specified to
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.Fn setrlimit
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would have
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raised the maximum limit value, and the caller is not the super-user.
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.El
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.Sh SEE ALSO
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.Xr csh 1 ,
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.Xr quota 1 ,
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.Xr quotactl 2 ,
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.Xr sigaltstack 2 ,
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.Xr sigvec 2 ,
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.Xr sysctl 3 ,
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.Xr ulimit 3
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.Sh HISTORY
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The
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.Fn getrlimit
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system call appeared in
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.Bx 4.2 .
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