NAME¶
machinectl - Control the systemd machine manager
SYNOPSIS¶
machinectl [OPTIONS...] {COMMAND} [NAME...]
DESCRIPTION¶
machinectl may be used to introspect and control the state
    of the systemd(1) virtual machine and container registration manager
    systemd-machined.service(8).
machinectl may be used to execute operations on machines
    and images. Machines in this sense are considered running instances of:
•Virtual Machines (VMs) that virtualize hardware
  to run full operating system (OS) instances (including their kernels) in a
  virtualized environment on top of the host OS.
•Containers that share the hardware and OS kernel
  with the host OS, in order to run OS userspace instances on top the host
  OS.
•The host system itself.
Machines are identified by names that follow the same rules as
    UNIX and DNS hostnames. For details, see below.
Machines are instantiated from disk or file system images that
    frequently — but not necessarily — carry the
    same name as machines running from them. Images in this sense may be:
•Directory trees containing an OS, including the
  top-level directories /usr/, /etc/, and so on.
•btrfs subvolumes containing OS trees, similar to
  regular directory trees.
•Binary "raw" disk image files
  containing MBR or GPT partition tables and Linux file systems.
•Similarly, block devices containing MBR or GPT
  partition tables and file systems.
•The file system tree of the host OS itself.
COMMANDS¶
The following commands are understood:
Machine Commands¶
list
List currently running (online) virtual machines and
  containers. To enumerate machine images that can be started, use
  list-images (see below). Note that this command hides the special
  ".host" machine by default. Use the --all switch to show
  it.
status NAME...
Show runtime status information about one or more virtual
  machines and containers, followed by the most recent log data from the
  journal. This function is intended to generate human-readable output. If you
  are looking for computer-parsable output, use show instead. Note that
  the log data shown is reported by the virtual machine or container manager,
  and frequently contains console output of the machine, but not necessarily
  journal contents of the machine itself.
show [NAME...]
Show properties of one or more registered virtual
  machines or containers or the manager itself. If no argument is specified,
  properties of the manager will be shown. If a NAME is specified, properties of
  this virtual machine or container are shown. By default, empty properties are
  suppressed. Use --all to show those too. To select specific properties
  to show, use --property=. This command is intended to be used whenever
  computer-parsable output is required, and does not print the control group
  tree or journal entries. Use status if you are looking for formatted
  human-readable output.
start NAME...
Start a container as a system service, using
  
systemd-nspawn(1). This starts systemd-nspawn@.service, instantiated
  for the specified machine name, similar to the effect of 
systemctl
  start on the service name. 
systemd-nspawn looks for a container
  image by the specified name in /var/lib/machines/ (and other search paths, see
  below) and runs it. Use 
list-images (see below) for listing available
  container images to start.
Note that systemd-machined.service(8) also interfaces with
    a variety of other container and VM managers, systemd-nspawn is just
    one implementation of it. Most of the commands available in
    machinectl may be used on containers or VMs controlled by other
    managers, not just systemd-nspawn. Starting VMs and container images
    on those managers requires manager-specific tools.
To interactively start a container on the command line with full
    access to the container's console, please invoke systemd-nspawn
    directly. To stop a running container use machinectl poweroff.
login [NAME]
Open an interactive terminal login session in a container
  or on the local host. If an argument is supplied, it refers to the container
  machine to connect to. If none is specified, or the container name is
  specified as the empty string, or the special machine name ".host"
  (see below) is specified, the connection is made to the local host instead.
  This will create a TTY connection to a specific container or the local host
  and asks for the execution of a getty on it. Note that this is only supported
  for containers running 
systemd(1) as init system.
This command will open a full login prompt on the container or the
    local host, which then asks for username and password. Use shell (see
    below) or systemd-run(1) with the --machine= switch to
    directly invoke a single command, either interactively or in the
  background.
shell [[NAME@]NAME [PATH
    [ARGUMENTS...]]]
Open an interactive shell session in a container or on
  the local host. The first argument refers to the container machine to connect
  to. If none is specified, or the machine name is specified as the empty
  string, or the special machine name ".host" (see below) is
  specified, the connection is made to the local host instead. This works
  similarly to 
login, but immediately invokes a user process. This
  command runs the specified executable with the specified arguments, or the
  default shell for the user if none is specified, or /bin/sh if no default
  shell is found. By default, 
--uid=, or by prefixing the machine name
  with a username and an "@" character, a different user may be
  selected. Use 
--setenv= to set environment variables for the executed
  process.
Note that machinectl shell does not propagate the exit
    code/status of the invoked shell process. Use systemd-run instead if
    that information is required (see below).
Using the shell command without arguments (thus invoking
    the executed shell or command on the local host), is in many ways similar to
    a su(1) session, but, unlike su, completely isolates the new
    session from the originating session, so that it shares no process or
    session properties and is in a clean well-defined state. It will be tracked
    in a new utmp, login, audit, security, and keyring sessions, and will not
    inherit any environment variables or resource limits, among other
    properties.
Note that systemd-run(1) with its --machine= switch
    may be used in place of the machinectl shell command, and allows
    non-interactive operation, more detailed and low-level configuration of the
    invoked unit, as well as access to runtime and exit code/status information
    of the invoked shell process. In particular, use systemd-run's
    --wait switch to propagate exit status information of the invoked
    process. Use systemd-run's --pty switch to acquire an
    interactive shell, similarly to machinectl shell. In general,
    systemd-run is preferable for scripting purposes. However, note that
    systemd-run might require higher privileges than machinectl
    shell.
enable NAME..., disable NAME...
Enable or disable a container as a system service to
  start at system boot, using 
systemd-nspawn(1). This enables or disables
  systemd-nspawn@.service, instantiated for the specified machine name,
  similarly to the effect of 
systemctl enable or 
systemctl disable
  on the service name.
This command implicitly reloads the system manager configuration
    after completing the operation. Note that this command does not implicitly
    start or power off the containers that are being operated on. If this is
    desired, combine the command with the --now switch.
poweroff NAME...
Power off one or more containers. This will trigger a
  reboot by sending SIGRTMIN+4 to the container's init process, which causes
  systemd-compatible init systems to shut down cleanly. Use 
stop as alias
  for 
poweroff. This operation does not work on containers that do not
  run a 
systemd(1)-compatible init system, such as sysvinit. Use
  
terminate (see below) to immediately terminate a container or VM,
  without cleanly shutting it down.
reboot NAME...
Reboot one or more containers. This will trigger a reboot
  by sending SIGINT to the container's init process, which is roughly equivalent
  to pressing Ctrl+Alt+Del on a non-containerized system, and is compatible with
  containers running any system manager.
terminate NAME...
Immediately terminates a virtual machine or container,
  without cleanly shutting it down. This kills all processes of the virtual
  machine or container and deallocates all resources attached to that instance.
  Use poweroff to issue a clean shutdown request.
kill NAME...
Send a signal to one or more processes of the virtual
  machine or container. This means processes as seen by the host, not the
  processes inside the virtual machine or container. Use --kill-whom= to
  select which process to kill. Use --signal= to select the signal to
  send.
bind NAME PATH [PATH]
Bind mounts a file or directory from the host into the
  specified container. The first path argument is the source file or directory
  on the host, the second path argument is the destination file or directory in
  the container. When the latter is omitted, the destination path in the
  container is the same as the source path on the host. When combined with the
  
--read-only switch, a ready-only bind mount is created. When combined
  with the 
--mkdir switch, the destination path is first created before
  the mount is applied. Note that this option is currently only supported for
  
systemd-nspawn(1) containers, and only if user namespacing
  (
--private-users) is not used. This command supports bind mounting
  directories, regular files, device nodes, 
AF_UNIX socket nodes, as well
  as FIFOs.
copy-to NAME PATH [PATH]
    --force
Copies files or directories from the host system into a
  running container. Takes a container name, followed by the source path on the
  host and the destination path in the container. If the destination path is
  omitted, the same as the source path is used.
If host and container share the same user and group namespace,
    file ownership by numeric user ID and group ID is preserved for the copy,
    otherwise all files and directories in the copy will be owned by the root
    user and group (UID/GID 0).
copy-from NAME PATH [PATH]
    --force
Copies files or directories from a container into the
  host system. Takes a container name, followed by the source path in the
  container and the destination path on the host. If the destination path is
  omitted, the same as the source path is used.
If host and container share the same user and group namespace,
    file ownership by numeric user ID and group ID is preserved for the copy,
    otherwise all files and directories in the copy will be owned by the root
    user and group (UID/GID 0).
Image Commands¶
list-images
Show a list of locally installed container and VM images.
  This enumerates all raw disk images and container directories and subvolumes
  in /var/lib/machines/ (and other search paths, see below). Use start
  (see above) to run a container off one of the listed images. Note that, by
  default, containers whose name begins with a dot (".") are not
  shown. To show these too, specify --all. Note that a special image
  ".host" always implicitly exists and refers to the image the host
  itself is booted from.
image-status [NAME...]
Show terse status information about one or more container
  or VM images. This function is intended to generate human-readable output. Use
  show-image (see below) to generate computer-parsable output
  instead.
show-image [NAME...]
Show properties of one or more registered virtual machine
  or container images, or the manager itself. If no argument is specified,
  properties of the manager will be shown. If a NAME is specified, properties of
  this virtual machine or container image are shown. By default, empty
  properties are suppressed. Use --all to show those too. To select
  specific properties to show, use --property=. This command is intended
  to be used whenever computer-parsable output is required. Use
  image-status if you are looking for formatted human-readable
  output.
edit NAME|FILE
Edit the settings file of the specified machines. For the
  format of the settings file, refer to 
systemd.nspawn(5). If an existing
  settings file of the given machine can't be found, 
edit automatically
  create a new settings file from scratch under /etc/systemd/nspawn/
cat NAME|FILE
Show the settings file of the specified machines.
clone NAME NAME
Clones a container or VM image. The arguments specify the
  name of the image to clone and the name of the newly cloned image. Note that
  plain directory container images are cloned into btrfs subvolume images with
  this command, if the underlying file system supports this. Note that cloning a
  container or VM image is optimized for file systems that support
  copy-on-write, and might not be efficient on others, due to file system
  limitations.
Note that this command leaves hostname, machine ID and all other
    settings that could identify the instance unmodified. The original image and
    the cloned copy will hence share these credentials, and it might be
    necessary to manually change them in the copy.
If combined with the --read-only switch a read-only cloned
    image is created.
rename NAME NAME
Renames a container or VM image. The arguments specify
  the name of the image to rename and the new name of the image.
read-only NAME [BOOL]
Marks or (unmarks) a container or VM image read-only.
  Takes a VM or container image name, followed by a boolean as arguments. If the
  boolean is omitted, positive is implied, i.e. the image is marked
  read-only.
remove NAME...
Removes one or more container or VM images. The special
  image ".host", which refers to the host's own directory tree, may
  not be removed.
set-limit [NAME] BYTES
Sets the maximum size in bytes that a specific container
  or VM image, or all images, may grow up to on disk (disk quota). Takes either
  one or two parameters. The first, optional parameter refers to a container or
  VM image name. If specified, the size limit of the specified image is changed.
  If omitted, the overall size limit of the sum of all images stored locally is
  changed. The final argument specifies the size limit in bytes, possibly
  suffixed by the usual K, M, G, T units. If the size limit shall be disabled,
  specify "-" as size.
Note that per-container size limits are only supported on btrfs
    file systems.
clean
Remove hidden VM or container images (or all). This
  command removes all hidden machine images from /var/lib/machines/, i.e. those
  whose name begins with a dot. Use 
machinectl list-images --all to see a
  list of all machine images, including the hidden ones.
When combined with the --all switch removes all images, not
    just hidden ones. This command effectively empties /var/lib/machines/.
Note that commands such as machinectl pull-tar or
    machinectl pull-raw usually create hidden, read-only, unmodified
    machine images from the downloaded image first, before cloning a writable
    working copy of it, in order to avoid duplicate downloads in case of images
    that are reused multiple times. Use machinectl clean to remove old,
    hidden images created this way.
Image Transfer Commands¶
pull-tar URL [NAME]
Downloads a .tar container image from the specified URL,
  and makes it available under the specified local machine name. The URL must be
  of type "
http://" or "
https://", and must refer to a .tar,
  .tar.gz, .tar.xz or .tar.bz2 archive file. If the local machine name is
  omitted, it is automatically derived from the last component of the URL, with
  its suffix removed.
The image is verified before it is made available, unless
    --verify=no is specified. Verification is done either via an inline
    signed file with the name of the image and the suffix .sha256 or via
    separate SHA256SUMS and SHA256SUMS.gpg files. The signature files need to be
    made available on the same web server, under the same URL as the .tar file.
    With --verify=checksum, only the SHA256 checksum for the file is
    verified, based on the .sha256 suffixed file or the SHA256SUMS file. With
    --verify=signature, the sha checksum file is first verified with the
    inline signature in the .sha256 file or the detached GPG signature file
    SHA256SUMS.gpg. The public key for this verification step needs to be
    available in /usr/lib/systemd/import-pubring.gpg or
    /etc/systemd/import-pubring.gpg.
The container image will be downloaded and stored in a read-only
    subvolume in /var/lib/machines/ that is named after the specified URL and
    its HTTP etag. A writable snapshot is then taken from this subvolume, and
    named after the specified local name. This behavior ensures that creating
    multiple container instances of the same URL is efficient, as multiple
    downloads are not necessary. In order to create only the read-only image,
    and avoid creating its writable snapshot, specify "-" as local
    machine name.
Note that the read-only subvolume is prefixed with .tar-, and is
    thus not shown by list-images, unless --all is passed.
Note that pressing C-c during execution of this command will not
    abort the download. Use cancel-transfer, described below.
pull-raw URL [NAME]
Downloads a .raw container or VM disk image from the
  specified URL, and makes it available under the specified local machine name.
  The URL must be of type "
http://" or "
https://". The
  container image must either be a .qcow2 or raw disk image, optionally
  compressed as .gz, .xz, or .bz2. If the local machine name is omitted, it is
  automatically derived from the last component of the URL, with its suffix
  removed.
Image verification is identical for raw and tar images (see
    above).
If the downloaded image is in .qcow2 format it is converted into a
    raw image file before it is made available.
Downloaded images of this type will be placed as read-only .raw
    file in /var/lib/machines/. A local, writable (reflinked) copy is then made
    under the specified local machine name. To omit creation of the local,
    writable copy pass "-" as local machine name.
Similarly to the behavior of pull-tar, the read-only image
    is prefixed with .raw-, and thus not shown by list-images, unless
    --all is passed.
Note that pressing C-c during execution of this command will not
    abort the download. Use cancel-transfer, described below.
import-tar FILE [NAME], import-raw
    FILE [NAME]
Imports a TAR or RAW container or VM image, and places it
  under the specified name in /var/lib/machines/. When 
import-tar is
  used, the file specified as the first argument should be a tar archive,
  possibly compressed with xz, gzip or bzip2. It will then be unpacked into its
  own subvolume in /var/lib/machines/. When 
import-raw is used, the file
  should be a qcow2 or raw disk image, possibly compressed with xz, gzip or
  bzip2. If the second argument (the resulting image name) is not specified, it
  is automatically derived from the file name. If the filename is passed as
  "-", the image is read from standard input, in which case the second
  argument is mandatory.
Optionally, the --read-only switch may be used to create a
    read-only container or VM image. No cryptographic validation is done when
    importing the images.
Much like image downloads, ongoing imports may be listed with
    list-transfers and aborted with cancel-transfer.
import-fs DIRECTORY [NAME]
Imports a container image stored in a local directory
  into /var/lib/machines/, operates similarly to import-tar or
  import-raw, but the first argument is the source directory. If
  supported, this command will create a btrfs snapshot or subvolume for the new
  image.
export-tar NAME [FILE], export-raw
    NAME [FILE]
Exports a TAR or RAW container or VM image and stores it
  in the specified file. The first parameter should be a VM or container image
  name. The second parameter should be a file path the TAR or RAW image is
  written to. If the path ends in ".gz", the file is compressed with
  gzip, if it ends in ".xz", with xz, and if it ends in
  ".bz2", with bzip2. If the path ends in neither, the file is left
  uncompressed. If the second argument is missing, the image is written to
  standard output. The compression may also be explicitly selected with the
  
--format= switch. This is in particular useful if the second parameter
  is left unspecified.
Much like image downloads and imports, ongoing exports may be
    listed with list-transfers and aborted with
  cancel-transfer.
Note that, currently, only directory and subvolume images may be
    exported as TAR images, and only raw disk images as RAW images.
list-transfers
Shows a list of container or VM image downloads, imports
  and exports that are currently in progress.
cancel-transfer ID...
Aborts a download, import or export of the container or
  VM image with the specified ID. To list ongoing transfers and their IDs, use
  list-transfers.
OPTIONS¶
The following options are understood:
-p, --property=
When showing machine or image properties, limit the
  output to certain properties as specified by the argument. If not specified,
  all set properties are shown. The argument should be a property name, such as
  "Name". If specified more than once, all properties with the
  specified names are shown.
-a, --all
When showing machine or image properties, show all
  properties regardless of whether they are set or not.
When listing VM or container images, do not suppress images
    beginning in a dot character (".").
When cleaning VM or container images, remove all images, not just
    hidden ones.
--value
When printing properties with show, only print the
  value, and skip the property name and "=".
-l, --full
Do not ellipsize process tree entries or table. This
  implies --max-addresses=full.
--kill-whom=
When used with kill, choose which processes to
  kill. Must be one of leader, or all to select whether to kill
  only the leader process of the machine or all processes of the machine. If
  omitted, defaults to all.
-s, --signal=
When used with 
kill, choose which signal to send
  to selected processes. Must be one of the well-known signal specifiers such as
  
SIGTERM, 
SIGINT or 
SIGSTOP. If omitted, defaults to
  
SIGTERM.
The special value "help" will list the known values and
    the program will exit immediately, and the special value "list"
    will list known values along with the numerical signal numbers and the
    program will exit immediately.
--uid=
When used with the shell command, chooses the user
  ID to open the interactive shell session as. If the argument to the
  shell command also specifies a user name, this option is ignored. If
  the name is not specified in either way, "root" will be used by
  default. Note that this switch is not supported for the login command
  (see below).
-E NAME[=VALUE],
    --setenv=NAME[=VALUE]
When used with the 
shell command, sets an
  environment variable for the executed shell. This option may be used more than
  once to set multiple variables. When "=" and 
VALUE are
  omitted, the value of the variable with the same name in the program
  environment will be used.
Note that this option is not supported for the login
    command.
--mkdir
When used with bind, creates the destination file
  or directory before applying the bind mount. Note that even though the name of
  this option suggests that it is suitable only for directories, this option
  also creates the destination file node to mount over if the object to mount is
  not a directory, but a regular file, device node, socket or FIFO.
--read-only
When used with 
bind, creates a read-only bind
  mount.
When used with clone, import-raw or
    import-tar a read-only container or VM image is created.
-n, --lines=
When used with status, controls the number of
  journal lines to show, counting from the most recent ones. Takes a positive
  integer argument. Defaults to 10.
-o, --output=
When used with 
status, controls the formatting of
  the journal entries that are shown. For the available choices, see
  
journalctl(1). Defaults to "short".
--verify=
When downloading a container or VM image, specify whether
  the image shall be verified before it is made available. Takes one of
  "no", "checksum" and "signature". If
  "no", no verification is done. If "checksum" is specified,
  the download is checked for integrity after the transfer is complete, but no
  signatures are verified. If "signature" is specified, the checksum
  is verified and the image's signature is checked against a local keyring of
  trustable vendors. It is strongly recommended to set this option to
  "signature" if the server and protocol support this. Defaults to
  "signature".
--now
When used with enable or disable, the
  containers will also be started or powered off. The start or poweroff
  operation is only carried out when the respective enable or disable operation
  has been successful.
--force
When downloading a container or VM image, and a local
  copy by the specified local machine name already exists, delete it first and
  replace it by the newly downloaded image.
--format=
When used with the export-tar or export-raw
  commands, specifies the compression format to use for the resulting file.
  Takes one of "uncompressed", "xz", "gzip",
  "bzip2". By default, the format is determined automatically from the
  image file name passed.
--max-addresses=
When used with the list-machines command, limits
  the number of IP addresses shown for every machine. Defaults to 1. All
  addresses can be requested with "all". If the limit is 0, the
  address column is not shown. Otherwise, if the machine has more addresses than
  shown, "..." follows the last address.
-q, --quiet
Suppresses additional informational output while
  running.
-H, --host=
Execute the operation remotely. Specify a hostname, or a
  username and hostname separated by "@", to connect to. The hostname
  may optionally be suffixed by a port ssh is listening on, separated by
  ":", and then a container name, separated by "/", which
  connects directly to a specific container on the specified host. This will use
  SSH to talk to the remote machine manager instance. Container names may be
  enumerated with machinectl -H HOST. Put IPv6 addresses in
  brackets.
-M, --machine=
--no-pager
Do not pipe output into a pager.
--no-legend
Do not print the legend, i.e. column headers and the
  footer with hints.
--no-ask-password
Do not query the user for authentication for privileged
  operations.
-h, --help
Print a short help text and exit.
--version
Print a short version string and exit.
MACHINE AND IMAGE NAMES¶
The machinectl tool operates on machines and images whose
    names must be chosen following strict rules. Machine names must be suitable
    for use as hostnames following a conservative subset of DNS and UNIX/Linux
    semantics. Specifically, they must consist of one or more non-empty label
    strings, separated by dots. No leading or trailing dots are allowed. No
    sequences of multiple dots are allowed. The label strings may only consist
    of alphanumeric characters as well as the dash and underscore. The maximum
    length of a machine name is 64 characters.
A special machine with the name ".host" refers to the
    running host system itself. This is useful for execution operations or
    inspecting the host system as well. Note that machinectl list will
    not show this special machine unless the --all switch is
  specified.
Requirements on image names are less strict, however, they must be
    valid UTF-8, must be suitable as file names (hence not be the single or
    double dot, and not include a slash), and may not contain control
    characters. Since many operations search for an image by the name of a
    requested machine, it is recommended to name images in the same strict
    fashion as machines.
A special image with the name ".host" refers to the
    image of the running host system. It hence conceptually maps to the special
    ".host" machine name described above. Note that machinectl
    list-images will not show this special image either, unless --all
    is specified.
FILES AND DIRECTORIES¶
Machine images are preferably stored in /var/lib/machines/, but
    are also searched for in /usr/local/lib/machines/ and /usr/lib/machines/.
    For compatibility reasons, the directory /var/lib/container/ is searched,
    too. Note that images stored below /usr/ are always considered read-only. It
    is possible to symlink machines images from other directories into
    /var/lib/machines/ to make them available for control with
    machinectl.
Note that some image operations are only supported, efficient or
    atomic on btrfs file systems.
Disk images are understood by systemd-nspawn(1) and
    machinectl in three formats:
•A simple directory tree, containing the files and
  directories of the container to boot.
•Subvolumes (on btrfs file systems), which are
  similar to the simple directories, described above. However, they have
  additional benefits, such as efficient cloning and quota reporting.
•"Raw" disk images, i.e. binary images
  of disks with a GPT or MBR partition table. Images of this type are regular
  files with the suffix ".raw".
See systemd-nspawn(1) for more information on image
    formats, in particular its --directory= and --image=
  options.
EXAMPLES¶
Example 1. Download a Ubuntu image and open a
    shell in it
This downloads and verifies the specified .tar image, and then
    uses systemd-nspawn(1) to open a shell in it.
Example 2. Download a Fedora image, set a root
    password in it, start it as a service
This downloads the specified .raw image with verification
    disabled. Then, a shell is opened in it and a root password is set.
    Afterwards the shell is left, and the machine started as system service.
    With the last command a login prompt into the container is requested.
Example 3. Exports a container image as tar
    file
# machinectl export-tar fedora myfedora.tar.xz
 
Exports the container "fedora" as an xz-compressed tar
    file myfedora.tar.xz into the current directory.
Example 4. Create a new shell session
# machinectl shell --uid=lennart
 
This creates a new shell session on the local host for the user ID
    "lennart", in a su(1)-like fashion.
EXIT STATUS¶
On success, 0 is returned, a non-zero failure code otherwise.
ENVIRONMENT¶
$SYSTEMD_LOG_LEVEL
The maximum log level of emitted messages (messages with
  a higher log level, i.e. less important ones, will be suppressed). Either one
  of (in order of decreasing importance) 
emerg, 
alert,
  
crit, 
err, 
warning, 
notice, 
info,
  
debug, or an integer in the range 0...7. See 
syslog(3) for more
  information.
$SYSTEMD_LOG_COLOR
A boolean. If true, messages written to the tty will be
  colored according to priority.
This setting is only useful when messages are written directly to
    the terminal, because journalctl(1) and other tools that display logs
    will color messages based on the log level on their own.
$SYSTEMD_LOG_TIME
A boolean. If true, console log messages will be prefixed
  with a timestamp.
This setting is only useful when messages are written directly to
    the terminal or a file, because journalctl(1) and other tools that
    display logs will attach timestamps based on the entry metadata on their
    own.
$SYSTEMD_LOG_LOCATION
A boolean. If true, messages will be prefixed with a
  filename and line number in the source code where the message originates.
Note that the log location is often attached as metadata to
    journal entries anyway. Including it directly in the message text can
    nevertheless be convenient when debugging programs.
$SYSTEMD_LOG_TID
A boolean. If true, messages will be prefixed with the
  current numerical thread ID (TID).
Note that the this information is attached as metadata to journal
    entries anyway. Including it directly in the message text can nevertheless
    be convenient when debugging programs.
$SYSTEMD_LOG_TARGET
The destination for log messages. One of 
console
  (log to the attached tty), 
console-prefixed (log to the attached tty
  but with prefixes encoding the log level and "facility", see
  
syslog(3), 
kmsg (log to the kernel circular log buffer),
  
journal (log to the journal), 
journal-or-kmsg (log to the
  journal if available, and to kmsg otherwise), 
auto (determine the
  appropriate log target automatically, the default), 
null (disable log
  output).
$SYSTEMD_LOG_RATELIMIT_KMSG
Whether to ratelimit kmsg or not. Takes a boolean.
  Defaults to "true". If disabled, systemd will not ratelimit messages
  written to kmsg.
$SYSTEMD_PAGER
Pager to use when 
--no-pager is not given;
  overrides 
$PAGER. If neither 
$SYSTEMD_PAGER nor 
$PAGER
  are set, a set of well-known pager implementations are tried in turn,
  including 
less(1) and 
more(1), until one is found. If no pager
  implementation is discovered no pager is invoked. Setting this environment
  variable to an empty string or the value "cat" is equivalent to
  passing 
--no-pager.
Note: if $SYSTEMD_PAGERSECURE is not set,
    $SYSTEMD_PAGER (as well as $PAGER) will be silently
  ignored.
$SYSTEMD_LESS
Override the options passed to 
less (by default
  "FRSXMK").
Users might want to change two options in particular:
K
This option instructs the pager to exit immediately when
  Ctrl+C is pressed. To allow 
less to handle Ctrl+C itself to switch back
  to the pager command prompt, unset this option.
If the value of $SYSTEMD_LESS does not include
    "K", and the pager that is invoked is less, Ctrl+C will be
    ignored by the executable, and needs to be handled by the pager.
X
This option instructs the pager to not send termcap
  initialization and deinitialization strings to the terminal. It is set by
  default to allow command output to remain visible in the terminal even after
  the pager exits. Nevertheless, this prevents some pager functionality from
  working, in particular paged output cannot be scrolled with the mouse.
See less(1) for more discussion.
$SYSTEMD_LESSCHARSET
Override the charset passed to less (by default
  "utf-8", if the invoking terminal is determined to be UTF-8
  compatible).
$SYSTEMD_PAGERSECURE
Takes a boolean argument. When true, the
  "secure" mode of the pager is enabled; if false, disabled. If
  
$SYSTEMD_PAGERSECURE is not set at all, secure mode is enabled if the
  effective UID is not the same as the owner of the login session, see
  
geteuid(2) and 
sd_pid_get_owner_uid(3). In secure mode,
  
LESSSECURE=1 will be set when invoking the pager, and the pager shall
  disable commands that open or create new files or start new subprocesses. When
  
$SYSTEMD_PAGERSECURE is not set at all, pagers which are not known to
  implement secure mode will not be used. (Currently only 
less(1)
  implements secure mode.)
Note: when commands are invoked with elevated privileges, for
    example under sudo(8) or pkexec(1), care must be taken to
    ensure that unintended interactive features are not enabled.
    "Secure" mode for the pager may be enabled automatically as
    describe above. Setting SYSTEMD_PAGERSECURE=0 or not removing it from
    the inherited environment allows the user to invoke arbitrary commands. Note
    that if the $SYSTEMD_PAGER or $PAGER variables are to be
    honoured, $SYSTEMD_PAGERSECURE must be set too. It might be
    reasonable to completely disable the pager using --no-pager
  instead.
$SYSTEMD_COLORS
Takes a boolean argument. When true, systemd and
  related utilities will use colors in their output, otherwise the output will
  be monochrome. Additionally, the variable can take one of the following
  special values: "16", "256" to restrict the use of colors
  to the base 16 or 256 ANSI colors, respectively. This can be specified to
  override the automatic decision based on $TERM and what the console is
  connected to.
$SYSTEMD_URLIFY
The value must be a boolean. Controls whether clickable
  links should be generated in the output for terminal emulators supporting
  this. This can be specified to override the decision that systemd makes
  based on $TERM and other conditions.