path: root/man/man5/limits.5

'\" t
.\"     Title: limits
.\"    Author: Luca Berra
.\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
.\"      Date: 01/23/2020
.\"    Manual: File Formats and Conversions
.\"    Source: shadow-utils 4.8.1
.\"  Language: English
.\"
.TH "LIMITS" "5" "01/23/2020" "shadow\-utils 4\&.8\&.1" "File Formats and Conversions"
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.\" http://lists.gnu.org/archive/html/groff/2009-02/msg00013.html
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.ie \n(.g .ds Aq \(aq
.el       .ds Aq '
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.nh
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.ad l
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.SH "NAME"
limits \- resource limits definition
.SH "DESCRIPTION"
.PP
The
\fIlimits\fR
file (/etc/limits
by default or LIMITS_FILE defined
config\&.h) describes the resource limits you wish to impose\&. It should be owned by root and readable by root account only\&.
.PP
By default no quota is imposed on \*(Aqroot\*(Aq\&. In fact, there is no way to impose limits via this procedure to root\-equiv accounts (accounts with UID 0)\&.
.PP
Each line describes a limit for a user in the form:
.PP
\fIuser LIMITS_STRING\fR
.PP
or in the form:
.PP
\fI@group LIMITS_STRING\fR
.PP
The
\fILIMITS_STRING\fR
is a string of a concatenated list of resource limits\&. Each limit consists of a letter identifier followed by a numerical limit\&.
.PP
The valid identifiers are:
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
A: max address space (KB)
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
C: max core file size (KB)
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
D: max data size (KB)
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
F: maximum file size (KB)
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
K: file creation mask, set by
\fBumask\fR(2)\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
I: max nice value (0\&.\&.39 which translates to 20\&.\&.\-19)
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
L: max number of logins for this user
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
M: max locked\-in\-memory address space (KB)
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
N: max number of open files
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
O: max real time priority
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
P: process priority, set by
\fBsetpriority\fR(2)\&.
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
R: max resident set size (KB)
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
S: max stack size (KB)
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
T: max CPU time (MIN)
.RE
.sp
.RS 4
.ie n \{\
\h'-04'\(bu\h'+03'\c
.\}
.el \{\
.sp -1
.IP \(bu 2.3
.\}
U: max number of processes
.RE
.PP
For example,
\fIL2D2048N5\fR
is a valid
\fILIMITS_STRING\fR\&. For reading convenience, the following entries are equivalent:
.sp
.if n \{\
.RS 4
.\}
.nf
      username L2D2048N5
      username L2 D2048 N5
    
.fi
.if n \{\
.RE
.\}
.PP
Be aware that after
\fIusername\fR
the rest of the line is considered a limit string, thus comments are not allowed\&. An invalid limits string will be rejected (not considered) by the
\fBlogin\fR
program\&.
.PP
The default entry is denoted by username "\fI*\fR"\&. If you have multiple
\fIdefault\fR
entries in your
\fILIMITS_FILE\fR, then the last one will be used as the default entry\&.
.PP
The limits specified in the form "\fI@group\fR" apply to the members of the specified
\fIgroup\fR\&.
.PP
If more than one line with limits for a user exist, only the first line for this user will be considered\&.
.PP
If no lines are specified for a user, the last
\fI@group\fR
line matching a group whose the user is a member of will be considered, or the last line with default limits if no groups contain the user\&.
.PP
To completely disable limits for a user, a single dash "\fI\-\fR" will do\&.
.PP
To disable a limit for a user, a single dash "\fI\-\fR" can be used instead of the numerical value for this limit\&.
.PP
Also, please note that all limit settings are set PER LOGIN\&. They are not global, nor are they permanent\&. Perhaps global limits will come, but for now this will have to do ;)
.SH "FILES"
.PP
/etc/limits
.RS 4
.RE
.SH "SEE ALSO"
.PP
\fBlogin\fR(1),
\fBsetpriority\fR(2),
\fBsetrlimit\fR(2)\&.