Linux systems.</para>
<para>When used in conjunction with <varname>DynamicUser=</varname> the user/group name specified is
- dynamically allocated at the time the service is started, and released at the time the service is stopped —
- unless it is already allocated statically (see below). If <varname>DynamicUser=</varname> is not used the
- specified user and group must have been created statically in the user database no later than the moment the
- service is started, for example using the
- <citerefentry><refentrytitle>sysusers.d</refentrytitle><manvolnum>5</manvolnum></citerefentry> facility, which
- is applied at boot or package install time.</para>
+ dynamically allocated at the time the service is started, and released at the time the service is
+ stopped — unless it is already allocated statically (see below). If <varname>DynamicUser=</varname>
+ is not used the specified user and group must have been created statically in the user database no
+ later than the moment the service is started, for example using the
+ <citerefentry><refentrytitle>sysusers.d</refentrytitle><manvolnum>5</manvolnum></citerefentry>
+ facility, which is applied at boot or package install time. If the user does not exist by then
+ program invocation will fail.</para>
<para>If the <varname>User=</varname> setting is used the supplementary group list is initialized
from the specified user's default group list, as defined in the system's user and group
<term><varname>LimitRTTIME=</varname></term>
<listitem><para>Set soft and hard limits on various resources for executed processes. See
- <citerefentry><refentrytitle>setrlimit</refentrytitle><manvolnum>2</manvolnum></citerefentry> for details on
- the resource limit concept. Resource limits may be specified in two formats: either as single value to set a
- specific soft and hard limit to the same value, or as colon-separated pair <option>soft:hard</option> to set
- both limits individually (e.g. <literal>LimitAS=4G:16G</literal>). Use the string <option>infinity</option> to
- configure no limit on a specific resource. The multiplicative suffixes K, M, G, T, P and E (to the base 1024)
- may be used for resource limits measured in bytes (e.g. LimitAS=16G). For the limits referring to time values,
- the usual time units ms, s, min, h and so on may be used (see
+ <citerefentry><refentrytitle>setrlimit</refentrytitle><manvolnum>2</manvolnum></citerefentry> for
+ details on the resource limit concept. Resource limits may be specified in two formats: either as
+ single value to set a specific soft and hard limit to the same value, or as colon-separated pair
+ <option>soft:hard</option> to set both limits individually (e.g. <literal>LimitAS=4G:16G</literal>).
+ Use the string <option>infinity</option> to configure no limit on a specific resource. The
+ multiplicative suffixes K, M, G, T, P and E (to the base 1024) may be used for resource limits
+ measured in bytes (e.g. <literal>LimitAS=16G</literal>). For the limits referring to time values, the
+ usual time units ms, s, min, h and so on may be used (see
<citerefentry><refentrytitle>systemd.time</refentrytitle><manvolnum>7</manvolnum></citerefentry> for
- details). Note that if no time unit is specified for <varname>LimitCPU=</varname> the default unit of seconds
- is implied, while for <varname>LimitRTTIME=</varname> the default unit of microseconds is implied. Also, note
- that the effective granularity of the limits might influence their enforcement. For example, time limits
- specified for <varname>LimitCPU=</varname> will be rounded up implicitly to multiples of 1s. For
- <varname>LimitNICE=</varname> the value may be specified in two syntaxes: if prefixed with <literal>+</literal>
- or <literal>-</literal>, the value is understood as regular Linux nice value in the range -20..19. If not
- prefixed like this the value is understood as raw resource limit parameter in the range 0..40 (with 0 being
- equivalent to 1).</para>
-
- <para>Note that most process resource limits configured with these options are per-process, and processes may
- fork in order to acquire a new set of resources that are accounted independently of the original process, and
- may thus escape limits set. Also note that <varname>LimitRSS=</varname> is not implemented on Linux, and
- setting it has no effect. Often it is advisable to prefer the resource controls listed in
+ details). Note that if no time unit is specified for <varname>LimitCPU=</varname> the default unit of
+ seconds is implied, while for <varname>LimitRTTIME=</varname> the default unit of microseconds is
+ implied. Also, note that the effective granularity of the limits might influence their
+ enforcement. For example, time limits specified for <varname>LimitCPU=</varname> will be rounded up
+ implicitly to multiples of 1s. For <varname>LimitNICE=</varname> the value may be specified in two
+ syntaxes: if prefixed with <literal>+</literal> or <literal>-</literal>, the value is understood as
+ regular Linux nice value in the range -20..19. If not prefixed like this the value is understood as
+ raw resource limit parameter in the range 0..40 (with 0 being equivalent to 1).</para>
+
+ <para>Note that most process resource limits configured with these options are per-process, and
+ processes may fork in order to acquire a new set of resources that are accounted independently of the
+ original process, and may thus escape limits set. Also note that <varname>LimitRSS=</varname> is not
+ implemented on Linux, and setting it has no effect. Often it is advisable to prefer the resource
+ controls listed in
<citerefentry><refentrytitle>systemd.resource-control</refentrytitle><manvolnum>5</manvolnum></citerefentry>
- over these per-process limits, as they apply to services as a whole, may be altered dynamically at runtime, and
- are generally more expressive. For example, <varname>MemoryLimit=</varname> is a more powerful (and working)
- replacement for <varname>LimitRSS=</varname>.</para>
-
- <para>For system units these resource limits may be chosen freely. For user units however (i.e. units run by a
- per-user instance of
- <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>), these limits are
- bound by (possibly more restrictive) per-user limits enforced by the OS.</para>
+ over these per-process limits, as they apply to services as a whole, may be altered dynamically at
+ runtime, and are generally more expressive. For example, <varname>MemoryMax=</varname> is a more
+ powerful (and working) replacement for <varname>LimitRSS=</varname>.</para>
<para>Resource limits not configured explicitly for a unit default to the value configured in the various
<varname>DefaultLimitCPU=</varname>, <varname>DefaultLimitFSIZE=</varname>, … options available in
<citerefentry><refentrytitle>systemd-system.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, and –
if not configured there – the kernel or per-user defaults, as defined by the OS (the latter only for user
- services, see above).</para>
+ services, see below).</para>
+
+ <para>For system units these resource limits may be chosen freely. When these settings are configured
+ in a user service (i.e. a service run by the per-user instance of the service manager) they cannot be
+ used to raise the limits above those set for the user manager itself when it was first invoked, as
+ the user's service manager generally lacks the privileges to do so. In user context these
+ configuration options are hence only useful to lower the limits passed in or to raise the soft limit
+ to the maximum of the hard limit as configured for the user. To raise the user's limits further, the
+ available configuration mechanisms differ between operating systems, but typically require
+ privileges. In most cases it is possible to configure higher per-user resource limits via PAM or by
+ setting limits on the system service encapsulating the user's service manager, i.e. the user's
+ instance of <filename>user@.service</filename>. After making such changes, make sure to restart the
+ user's service manager.</para>
<table>
<title>Resource limit directives, their equivalent <command>ulimit</command> shell commands and the unit used</title>
projects / thirdparty / systemd.git / blobdiff