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Diffstat (limited to 'man/systemd.exec.xml')
| -rw-r--r-- | man/systemd.exec.xml | 36 |
1 files changed, 32 insertions, 4 deletions
diff --git a/man/systemd.exec.xml b/man/systemd.exec.xml index 41ae6e76de..58ba582911 100644 --- a/man/systemd.exec.xml +++ b/man/systemd.exec.xml @@ -143,10 +143,38 @@ <term><varname>User=</varname></term> <term><varname>Group=</varname></term> - <listitem><para>Sets the Unix user or group that the processes - are executed as, respectively. Takes a single user or group - name or ID as argument. If no group is set, the default group - of the user is chosen. These do not affect commands prefixed with <literal>+</literal>.</para></listitem> + <listitem><para>Set the UNIX user or group that the processes are executed as, respectively. Takes a single + user or group name, or numeric ID as argument. If no group is set, the default group of the user is used. This + setting does not affect commands whose command line is prefixed with <literal>+</literal>.</para></listitem> + </varlistentry> + + <varlistentry> + <term><varname>DynamicUser=</varname></term> + + <listitem><para>Takes a boolean parameter. If set, a UNIX user and group pair is allocated dynamically when the + unit is started, and released as soon as it is stopped. The user and group will not be added to + <filename>/etc/passwd</filename> or <filename>/etc/group</filename>, but are managed transiently during + runtime. The <citerefentry><refentrytitle>nss-systemd</refentrytitle><manvolnum>8</manvolnum></citerefentry> + glibc NSS module provides integration of these dynamic users/groups into the system's user and group + databases. The user and group name to use may be configured via <varname>User=</varname> and + <varname>Group=</varname> (see above). If these options are not used and dynamic user/group allocation is + enabled for a unit, the name of the dynamic user/group is implicitly derived from the unit name. If the unit + name without the type suffix qualifies as valid user name it is used directly, otherwise a name incorporating a + hash of it is used. If a statically allocated user or group of the configured name already exists, it is used + and no dynamic user/group is allocated. Dynamic users/groups are allocated from the UID/GID range + 61184…65519. It is recommended to avoid this range for regular system or login users. At any point in time + each UID/GID from this range is only assigned to zero or one dynamically allocated users/groups in + use. However, UID/GIDs are recycled after a unit is terminated. Care should be taken that any processes running + as part of a unit for which dynamic users/groups are enabled do not leave files or directories owned by these + users/groups around, as a different unit might get the same UID/GID assigned later on, and thus gain access to + these files or directories. If <varname>DynamicUser=</varname> is enabled, <varname>PrivateTmp=</varname> is + implied. This ensures that the lifetime of temporary files created by the executed processes is bound to the + runtime of the service, and hence the lifetime of the dynamic user/group. Since <filename>/tmp</filename> and + <filename>/var/tmp</filename> are usually the only world-writable directories on a system this ensures that a + unit making use of dynamic user/group allocation cannot leave files around after unit termination. Use + <varname>RuntimeDirectory=</varname> (see below) in order to assign a writable runtime directory to a service, + owned by the dynamic user/group and removed automatically when the unit is terminated. Defaults to + off.</para></listitem> </varlistentry> <varlistentry> |