LIMITS.CONF(5) Linux-PAM Manual LIMITS.CONF(5)
limits.conf - configuration file for the pam_limits module
The syntax of the lines is as follows:
<domain> <type> <item> <value>
The fields listed above should be filled as follows:
o a username
o a groupname, with @group syntax. This should not be confused with netgroups.
o the wildcard *, for default entry.
o the wildcard %, for maxlogins limit only, can also be used with %group syntax.
NOTE: group and wildcard limits are not applied to the root user. To set a limit for
the root user, this field must contain the literal username root.
for enforcing hard resource limits. These limits are set by the superuser and
enforced by the Kernel. The user cannot raise his requirement of system resources
above such values.
for enforcing soft resource limits. These limits are ones that the user can move
up or down within the permitted range by any pre-existing hard limits. The values
specified with this token can be thought of as default values, for normal system
for enforcing both soft and hard resource limits together.
Note, if you specify a type of '-' but neglect to supply the item and value fields
then the module will never enforce any limits on the specified user/group etc. .
limits the core file size (KB)
maximum data size (KB)
maximum filesize (KB)
maximum locked-in-memory address space (KB)
maximum number of open files
maximum resident set size (KB) (Ignored in Linux 2.4.30 and higher)
maximum stack size (KB)
maximum CPU time (minutes)
maximum number of processes
address space limit (KB)
maximum number of logins for this user except for this with uid=0
maximum number of logins on system
the priority to run user process with (negative values boost process priority)
maximum locked files (Linux 2.4 and higher)
maximum number of pending signals (Linux 2.6 and higher)
maximum memory used by POSIX message queues (bytes) (Linux 2.6 and higher)
maximum nice priority allowed to raise to (Linux 2.6.12 and higher) values:
maximum realtime priority allowed for non-privileged processes (Linux 2.6.12 and
the directory to chroot the user to
All items support the values -1, unlimited or infinity indicating no limit, except for
priority and nice.
If a hard limit or soft limit of a resource is set to a valid value, but outside of the
supported range of the local system, the system may reject the new limit or unexpected
behavior may occur. If the control value required is used, the module will reject the
login if a limit could not be set.
In general, individual limits have priority over group limits, so if you impose no limits
for admin group, but one of the members in this group have a limits line, the user will
have its limits set according to this line.
Also, please note that all limit settings are set per login. They are not global, nor are
they permanent; existing only for the duration of the session.
In the limits configuration file, the '#' character introduces a comment - after which the
rest of the line is ignored.
The pam_limits module does report configuration problems found in its configuration file
and errors via syslog(3).
These are some example lines which might be specified in /etc/security/limits.conf.
* soft core 0
root hard core 100000
* hard rss 10000
@student hard nproc 20
@faculty soft nproc 20
@faculty hard nproc 50
ftp hard nproc 0
@student - maxlogins 4
pam_limits(8), pam.d(5), pam(7), getrlimit(2) getrlimit(3p)
pam_limits was initially written by Cristian Gafton <email@example.com>
Linux-PAM Manual 05/31/2011 LIMITS.CONF(5)