SYSUSERS.D(5) sysusers.d SYSUSERS.D(5)
NAME
sysusers.d - Declarative allocation of system users and groups
SYNOPSIS
/etc/sysusers.d/*.conf
/run/sysusers.d/*.conf
/usr/lib/sysusers.d/*.conf
#Type Name ID GECOS Home directory Shell
u user_name uid "User Description" /path/to/shell
u user_name uid:gid - -
u user_name /file/owned/by/user - -
g group_name gid "Group Description"
g group_name /file/owned/by/group -
m user_name group_name
r - lowest-highest
DESCRIPTION
systemd-sysusers uses the files from sysusers.d directory to create
system users and groups and to add users to 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 (i.e.
regular, "human") 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 DIRECTORIES AND PRECEDENCE
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.
Files in /etc/sysusers.d override files with the same name in
/usr/lib/sysusers.d and /run/sysusers.d. Files in /run/sysusers.d
override files with the same name in /usr/lib/sysusers.d. Packages
should install their configuration files in /usr/lib/sysusers.d. Files
in /etc/sysusers.d 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 path, the entry in the file with
the lexicographically earliest name will be applied. All later entries
for the same user and group names will be logged as warnings.
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
/etc/sysusers.d/ bearing the same filename.
CONFIGURATION FILE FORMAT
The file format is one line per user or group containing name, ID,
GECOS field description, home directory, and login shell:
#Type Name ID GECOS Home directory Shell
u httpd 404 "HTTP User"
u _authd /usr/bin/authd "Authorization user"
u postgres - "Postgresql Database" /var/lib/pgsql /libexec/postgresdb
g input - -
m _authd input
u root 0 "Superuser" /root /bin/zsh
r - 500-900
Empty lines and lines beginning with the "#" character are ignored, and
may be used for commenting.
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 unless the ID field specifies it. 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 creates 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. The specified name
must consist only of the characters a-z, A-Z, 0-9, "_" and "-", except
for the first character which must be one of a-z, A-Z or "_" (i.e.
numbers and "-" are not permitted as first character). The user/group
name must have at least one character, and at most 31.
For further details about the syntax of user/group names, see
User/Group Name Syntax[1].
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
(this is strongly recommended unless it is strictly necessary to use a
specific UID or GID). 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). The
syntaxes "uid:gid" and "uid:groupname" are supported to allow creating
users with specific primary groups. The given group must be created
explicitly, or it must already exist. Specifying "-" for the UID in
these syntaxes is also supported.
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
"-").
Home Directory
The home directory for a new system user. If omitted, defaults to the
root directory.
Only applies to lines of type u and should otherwise be left unset (or
"-"). It is recommended to omit this, unless software strictly requires
a home directory to be set.
Shell
The login shell of the user. If not specified, this will be set to
/usr/sbin/nologin, except if the UID of the user is 0, in which case
/bin/sh will be used.
Only applies to lines of type u and should otherwise be left unset (or
"-"). It is recommended to omit this, unless a shell different
/usr/sbin/nologin must be used.
SPECIFIERS
Specifiers can be used in the "Name", "ID", "GECOS", "Home directory",
and "Shell" fields. An unknown or unresolvable specifier is treated as
invalid configuration. The following expansions are understood:
Table 1. Specifiers available
+----------+-----------------+---------------------+
|Specifier | Meaning | Details |
+----------+-----------------+---------------------+
|"%b" | Boot ID | The boot ID of the |
| | | running system, |
| | | formatted as |
| | | string. See |
| | | random(4) for more |
| | | information. |
+----------+-----------------+---------------------+
|"%H" | Host name | The hostname of the |
| | | running system. |
+----------+-----------------+---------------------+
|"%m" | Machine ID | The machine ID of |
| | | the running system, |
| | | formatted as |
| | | string. See |
| | | machine-id(5) for |
| | | more information. |
+----------+-----------------+---------------------+
|"%T" | Directory for | This is either /tmp |
| | temporary files | or the path |
| | | "$TMPDIR", "$TEMP" |
| | | or "$TMP" are set |
| | | to. |
+----------+-----------------+---------------------+
|"%v" | Kernel release | Identical to uname |
| | | -r output. |
+----------+-----------------+---------------------+
|"%V" | Directory for | This is either |
| | larger and | /var/tmp or the |
| | persistent | path "$TMPDIR", |
| | temporary files | "$TEMP" or "$TMP" |
| | | are set to. |
+----------+-----------------+---------------------+
|"%%" | Escaped "%" | Single percent |
| | | sign. |
+----------+-----------------+---------------------+
IDEMPOTENCE
Note that systemd-sysusers will do nothing if the specified users or
groups already exist or the users are members of specified groups, 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)
NOTES
1. User/Group Name Syntax
https://systemd.io/USER_NAMES
systemd 245 SYSUSERS.D(5)