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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