%b Boot ID The boot ID of the running system, formatted as string. See random4 for more information. %a Architecture A short string identifying the architecture of the local system. A string such as x86, x86-64 or arm64. See the architectures defined for ConditionArchitecture= in systemd.unit5 for a full list. %B Operating system build ID The operating system build identifier of the running system, as read from the BUILD_ID= field of /etc/os-release. If not set, resolves to an empty string. See os-release5 for more information. %H Host name The hostname of the running system. %l Short host name The hostname of the running system, truncated at the first dot to remove any domain component. %m Machine ID The machine ID of the running system, formatted as string. See machine-id5 for more information. %o Operating system ID The operating system identifier of the running system, as read from the ID= field of /etc/os-release. See os-release5 for more information. %T Directory for temporary files This is either /tmp or the path $TMPDIR, $TEMP or $TMP are set to. (Note that the directory may be specified without a trailing slash.) %v Kernel release Identical to uname -r output. %V Directory for larger and persistent temporary files This is either /var/tmp or the path $TMPDIR, $TEMP or $TMP are set to. (Note that the directory may be specified without a trailing slash.) %w Operating system version ID The operating system version identifier of the running system, as read from the VERSION_ID= field of /etc/os-release. If not set, resolves to an empty string. See os-release5 for more information. %W Operating system variant ID The operating system variant identifier of the running system, as read from the VARIANT_ID= field of /etc/os-release. If not set, resolves to an empty string. See os-release5 for more information. %% Single percent sign Use %% in place of % to specify a single percent sign.