#language en
~-[[DebianWiki/EditorGuide#translation|Translation(s)]]: English - [[fr/Limits|Français]] - [[it/Limits|Italiano]]-~
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Unix operating system can enforce "Limits" the resources a process/user can consume.

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== pam_limits ==

In Debian, {{{pam_limits}}} enforce the limits when a session is opened. The limits are defined in {{{/etc/security/limits.conf}}}, see [[DebianMan:5/limits.conf|limits.conf(5)]] and {{{/etc/pam.d/*}}}.

Note that {{{pam_limits}}} is not used in {{{/etc/pam.d/common-session}}} and {{{/etc/pam.d/common-session-noninteractive}}}, so it won't be active for daemons (it is in PAM configuration for atd, cron, login, sshd, su, sudo, ...). For example, {{{apache2}}} limits are configured in {{{/etc/apache2/envvars}}} (see DebianBug:615632).

== ulimit ==
Any user can change it's own ''soft'' limit, between "zero", and the hard limit (typically enforced by pam_limit). For instance, [[DebianMan:1/bash|bash(1)]] has {{{ulimit}}} :

{{{
## Show the current Hard limit for "memlock"
$ ulimit -H -l
64

## Show the current Soft limit for "memlock"
$ ulimit -S -l
64

## Set the current Soft "memlock" limit to 48KiB
$ ulimit -S -l 48

## That's ok !
$ ulimit -S -l
48

## The hard limit is still 64K
$ ulimit -H -l

## And it isn't possible to change it
$ ulimit -H -l 128
bash: ulimit: max locked memory: cannot modify limit: Operation not permitted
}}}

List all hard limits:
{{{
$ ulimit -H -a
core file size          (blocks, -c) unlimited
data seg size           (kbytes, -d) unlimited
scheduling priority             (-e) 0
file size               (blocks, -f) unlimited
pending signals                 (-i) 16382
max locked memory       (kbytes, -l) 64
max memory size         (kbytes, -m) unlimited
open files                      (-n) 1024
pipe size            (512 bytes, -p) 8
POSIX message queues     (bytes, -q) 819200
real-time priority              (-r) 0
stack size              (kbytes, -s) unlimited
cpu time               (seconds, -t) unlimited
max user processes              (-u) unlimited
virtual memory          (kbytes, -v) unlimited
file locks                      (-x) unlimited
}}}

== Documentations ==
 * [[DebianMan:5/limits.conf|limits.conf(5)]]
 * [[DebianMan:1/bash|bash(1)]]

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== See also ==
 * DebianPkg:quota - implementation of the disk quota system

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