The following options are understood:

--root=root

Takes a directory path as an argument. All paths will be prefixed with the given alternate root path, including config search paths.

Added in version 215.

--image=image

Takes a path to a disk image file or block device node. If specified all operations are applied to file system in the indicated disk image. This is similar to --root= but operates on file systems stored in disk images or block devices. The disk image should either contain just a file system or a set of file systems within a GPT partition table, following the Discoverable Partitions Specification[1]. For further information on supported disk images, see systemd-nspawn(1)s switch of the same name.

Added in version 247.

--image-policy=policy

Takes an image policy string as argument, as per systemd.image-policy(7). The policy is enforced when operating on the disk image specified via --image=, see above. If not specified defaults to the "*" policy, i.e. all recognized file systems in the image are used.

--replace=PATH

When this option is given, one or more positional arguments must be specified. All configuration files found in the directories listed in sysusers.d(5) will be read, and the configuration given on the command line will be handled instead of and with the same priority as the configuration file PATH.

This option is intended to be used when package installation scripts are running and files belonging to that package are not yet available on disk, so their contents must be given on the command line, but the admin configuration might already exist and should be given higher priority.

Example 1. RPM installation script for radvd

.RS 4

echo u radvd - "radvd daemon" | \
          systemd-sysusers --replace=/usr/lib/sysusers.d/radvd.conf -

.RE

This will create the radvd user as if /usr/lib/sysusers.d/radvd.conf was already on disk. An admin might override the configuration specified on the command line by placing /etc/sysusers.d/radvd.conf or even /etc/sysusers.d/00-overrides.conf.

Note that this is the expanded form, and when used in a package, this would be written using a macro with "radvd" and a file containing the configuration line as arguments.

Added in version 238.

--dry-run

Process the configuration and figure out what entries would be created, but dont actually write anything.

Added in version 250.

--inline

Treat each positional argument as a separate configuration line instead of a file name.

Added in version 238.

--cat-config

Copy the contents of config files to standard output. Before each file, the filename is printed as a comment.

--tldr

Copy the contents of config files to standard output. Only the "interesting" parts of the configuration files are printed, comments and empty lines are skipped. Before each file, the filename is printed as a comment.

--no-pager

Do not pipe output into a pager.

-h, --help

Print a short help text and exit.

--version

Print a short version string and exit.

systemd-sysusers supports the service credentials logic as implemented by ImportCredential=/LoadCredential=/SetCredential= (see systemd.exec(1) for details). The following credentials are used when passed in:

passwd.hashed-password.user

A UNIX hashed password string to use for the specified user, when creating an entry for it. This is particularly useful for the "root" user as it allows provisioning the default root password to use via a unit file drop-in or from a container manager passing in this credential. Note that setting this credential has no effect if the specified user account already exists. This credential is hence primarily useful in first boot scenarios or systems that are fully stateless and come up with an empty /etc/ on every boot.

Added in version 249.

passwd.plaintext-password.user

Similar to "passwd.hashed-password.user" but expect a literal, plaintext password, which is then automatically hashed before used for the user account. If both the hashed and the plaintext credential are specified for the same user the former takes precedence. Its generally recommended to specify the hashed version; however in test environments with weaker requirements on security it might be easier to pass passwords in plaintext instead.

Added in version 249.

passwd.shell.user

Specifies the shell binary to use for the specified account when creating it.

Added in version 249.

sysusers.extra

The contents of this credential may contain additional lines to operate on. The credential contents should follow the same format as any other sysusers.d/ drop-in. If this credential is passed it is processed after all of the drop-in files read from the file system.

Added in version 252.

Note that by default the systemd-sysusers.service unit file is set up to inherit the "passwd.hashed-password.root", "passwd.plaintext-password.root", "passwd.shell.root" and "sysusers.extra" credentials from the service manager. Thus, when invoking a container with an unpopulated /etc/ for the first time it is possible to configure the root users password to be "systemd" like this:

.RS 4

# systemd-nspawn --image=... --set-credential=passwd.hashed-password.root:$y$j9T$yAuRJu1o5HioZAGDYPU5d.$F64ni6J2y2nNQve90M/p0ZP0ECP/qqzipNyaY9fjGpC ...

.RE

Note again that the data specified in this credential is consulted only when creating an account for the first time, it may not be used for changing the password or shell of an account that already exists.

Use mkpasswd(1) for generating UNIX password hashes from the command line.

On success, 0 is returned, a non-zero failure code otherwise.

1.

Discoverable Partitions Specification

https://uapi-group.org/specifications/specs/discoverable_partitions_specification

2.

Users, Groups, UIDs and GIDs on systemd systems

https://systemd.io/UIDS-GIDS