sysusers.d(5)

NAME

   sysusers.d - Declarative allocation of system users and groups

SYNOPSIS

   /usr/lib/sysusers.d/*.conf

DESCRIPTION

   systemd-sysusers uses the files from sysusers.d directory to create
   system users and groups at package installation or boot time. This tool
   may be used to allocate system users and groups only, it is not useful
   for creating non-system users and groups, as it accesses /etc/passwd
   and /etc/group directly, bypassing any more complex user databases, for
   example any database involving NIS or LDAP.

CONFIGURATION FORMAT

   Each configuration file shall be named in the style of package.conf or
   package-part.conf. The second variant should be used when it is
   desirable to make it easy to override just this part of configuration.

   The file format is one line per user or group containing name, ID,
   GECOS field description and home directory:

       # Type Name ID GECOS
       u httpd 440 "HTTP User"
       u authd /usr/bin/authd "Authorization user"
       g input - -
       m authd input
       u root 0 "Superuser" /root

   Type
   The type consists of a single letter. The following line types are
   understood:

   u
       Create a system user and group of the specified name should they
       not exist yet. The user's primary group will be set to the group
       bearing the same name. The user's shell will be set to
       /sbin/nologin, the home directory to the specified home directory,
       or / if none is given. The account will be created disabled, so
       that logins are not allowed.

   g
       Create a system group of the specified name should it not exist
       yet. Note that u implicitly create a matching group. The group will
       be created with no password set.

   m
       Add a user to a group. If the user or group do not exist yet, they
       will be implicitly created.

   r
       Add a range of numeric UIDs/GIDs to the pool to allocate new UIDs
       and GIDs from. If no line of this type is specified, the range of
       UIDs/GIDs is set to some compiled-in default. Note that both UIDs
       and GIDs are allocated from the same pool, in order to ensure that
       users and groups of the same name are likely to carry the same
       numeric UID and GID.

   Name
   The name field specifies the user or group name. It should be shorter
   than 31 characters and avoid any non-ASCII characters, and not begin
   with a numeric character. It is strongly recommended to pick user and
   group names that are unlikely to clash with normal users created by the
   administrator. A good scheme to guarantee this is by prefixing all
   system and group names with the underscore, and avoiding too generic
   names.

   For m lines, this field should contain the user name to add to a group.

   For lines of type r, this field should be set to "-".

   ID
   For u and g, the numeric 32-bit UID or GID of the user/group. Do not
   use IDs 65535 or 4294967295, as they have special placeholder meanings.
   Specify "-" for automatic UID/GID allocation for the user or group.
   Alternatively, specify an absolute path in the file system. In this
   case, the UID/GID is read from the path's owner/group. This is useful
   to create users whose UID/GID match the owners of pre-existing files
   (such as SUID or SGID binaries).

   For m lines, this field should contain the group name to add to a user
   to.

   For lines of type r, this field should be set to a UID/GID range in the
   format "FROM-TO", where both values are formatted as decimal ASCII
   numbers. Alternatively, a single UID/GID may be specified formatted as
   decimal ASCII numbers.

   GECOS
   A short, descriptive string for users to be created, enclosed in
   quotation marks. Note that this field may not contain colons.

   Only applies to lines of type u and should otherwise be left unset, or
   be set to "-".

   Home Directory
   The home directory for a new system user. If omitted, defaults to the
   root directory. It is recommended to not unnecessarily specify home
   directories for system users, unless software strictly requires one to
   be set.

   Only applies to lines of type u and should otherwise be left unset, or
   be set to "-".

CONFIGURATION DIRECTORIES AND PRECEDENCE

   Configuration files are read from directories in /etc/, /run/, and
   /lib/, in order of precedence. Each configuration file in these
   configuration directories shall be named in the style of filename.conf.
   Files in /etc/ override files with the same name in /run/ and /lib/.
   Files in /run/ override files with the same name in /lib/.

   Packages should install their configuration files in /lib/. Files in
   /etc/ are reserved for the local administrator, who may use this logic
   to override the configuration files installed by vendor packages. All
   configuration files are sorted by their filename in lexicographic
   order, regardless of which of the directories they reside in. If
   multiple files specify the same option, the entry in the file with the
   lexicographically latest name will take precedence. It is recommended
   to prefix all filenames with a two-digit number and a dash, to simplify
   the ordering of the files.

   If the administrator wants to disable a configuration file supplied by
   the vendor, the recommended way is to place a symlink to /dev/null in
   the configuration directory in /etc/, with the same filename as the
   vendor configuration file. If the vendor configuration file is included
   in the initrd image, the image has to be regenerated.

IDEMPOTENCE

   Note that systemd-sysusers will do nothing if the specified users or
   groups already exist, so normally, there is no reason to override
   sysusers.d vendor configuration, except to block certain users or
   groups from being created.

SEE ALSO

   systemd(1), systemd-sysusers(8)

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