`%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.unit 5 for a full list.
`%A` Operating system image version The operating system image version identifier of the running system, as read from the `IMAGE_VERSION=` field of `/etc/os-release`. If not set, resolves to an empty string. See os-release 5 for more information.
`%b` Boot ID The boot ID of the running system, formatted as string. See random 4 for more information.
`%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-release 5 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-id 5 for more information.
`%M` Operating system image identifier The operating system image identifier of the running system, as read from the `IMAGE_ID=` field of `/etc/os-release`. If not set, resolves to an empty string. See os-release 5 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-release 5 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-release 5 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-release 5 for more information.
`%%` Single percent sign Use `%%` in place of `%` to specify a single percent sign.