core: rework unit printing and implement 'combined' format

The code to print unit status formats had a long history, and became a
hard-to-manage mess of duplicate code parts. We would use sprintf() to
format a string, and then call sprintf() again… The code is reworked
to avoid repeated formattings and to streamline printing to the log
and the console.

The approach used in this patch is a bit more complex then in patches by Colin
Walter and Paweł Marciniak, because an allocation is only done if "combined"
format is used. In other cases we return the existing ->id or ->description
strings. The caller can also control whether a shorter or longer status string
should be used. This way the caller can use a shorter format where it makes
sense, for example in the cylon eye output, where we don't have enough
horizontal space.

Patch is based on Colin Walters' https://github.com/systemd/systemd/pull/15957,
and Paweł Marciniak's patch posted on fedora-devel.

Note: for some reason, the functions for printing of start and stop messages
were sepearated by some unrelated functions. They are moved to be consecutive,
but this makes the much more verbose than it would be otherwise. I found it
useful to view in gitk's "new" mode.

Co-authored-by: Colin Walters <walters@verbum.org>
Co-authored-by: Paweł Marciniak <sunwire+git@gmail.com>

Output from a Fedora Rawhide container boot (w/ some follow-up patches to
tweak Descriptions):

Welcome to Fedora 35 (Rawhide Prerelease)!

Queued start job for default target graphical.target.
[  OK  ] Created slice system-getty.slice - Slice /system/getty.
[  OK  ] Created slice system-modprobe.slice - Slice /system/modprobe.
[  OK  ] Created slice system-sshd\x2dkeygen.slice - Slice /system/sshd-keygen.
[  OK  ] Created slice user.slice - User and Session Slice.
[  OK  ] Started systemd-ask-password-console.path - Dispatch Password Requests to Console Directory Watch.
[  OK  ] Started systemd-ask-password-wall.path - Forward Password Requests to Wall Directory Watch.
[  OK  ] Reached target cryptsetup.target - Local Encrypted Volumes.
[  OK  ] Reached target paths.target - Path Units.
[  OK  ] Reached target remote-cryptsetup.target - Remote Encrypted Volumes.
[  OK  ] Reached target remote-fs.target - Remote File Systems.
[  OK  ] Reached target slices.target - Slice Units.
[  OK  ] Reached target swap.target - Swaps.
[  OK  ] Reached target veritysetup.target - Local Verity Integrity Protected Volumes.
[  OK  ] Listening on systemd-coredump.socket - Process Core Dump Socket.
[  OK  ] Listening on systemd-initctl.socket - initctl Compatibility Named Pipe.
[  OK  ] Listening on systemd-journald-dev-log.socket - Journal Socket (/dev/log).
[  OK  ] Listening on systemd-journald.socket - Journal Socket.
[  OK  ] Listening on systemd-networkd.socket - Network Service Netlink Socket.
[  OK  ] Listening on systemd-userdbd.socket - User Database Manager Socket.
         Mounting dev-hugepages.mount - Huge Pages File System...
         Starting systemd-journald.service - Journal Service...
         Starting systemd-remount-fs.service - Remount Root and Kernel File Systems...
         Starting systemd-sysctl.service - Apply Kernel Variables...
[  OK  ] Mounted dev-hugepages.mount - Huge Pages File System.
[  OK  ] Finished systemd-remount-fs.service - Remount Root and Kernel File Systems.
         Starting systemd-hwdb-update.service - Rebuild Hardware Database...
         Starting systemd-sysusers.service - Create System Users...
[  OK  ] Finished systemd-sysctl.service - Apply Kernel Variables.
[  OK  ] Started systemd-journald.service - Journal Service.
         Starting systemd-journal-flush.service - Flush Journal to Persistent Storage...
[  OK  ] Finished systemd-sysusers.service - Create System Users.
         Starting systemd-tmpfiles-setup-dev.service - Create Static Device Nodes in /dev...
[  OK  ] Finished systemd-tmpfiles-setup-dev.service - Create Static Device Nodes in /dev.
[  OK  ] Reached target local-fs-pre.target - Preparation for Local File Systems.
[  OK  ] Reached target local-fs.target - Local File Systems.
[  OK  ] Reached target machines.target - Containers.
         Starting dracut-shutdown.service - Restore /run/initramfs on shutdown...
         Starting ldconfig.service - Rebuild Dynamic Linker Cache...
[  OK  ] Finished dracut-shutdown.service - Restore /run/initramfs on shutdown.
[  OK  ] Finished ldconfig.service - Rebuild Dynamic Linker Cache.
[  OK  ] Finished systemd-journal-flush.service - Flush Journal to Persistent Storage.
         Starting systemd-tmpfiles-setup.service - Create Volatile Files and Directories...
[  OK  ] Finished systemd-tmpfiles-setup.service - Create Volatile Files and Directories.
         Starting systemd-journal-catalog-update.service - Rebuild Journal Catalog...
         Starting systemd-oomd.service - Userspace Out-Of-Memory (OOM) Killer...
         Starting systemd-update-utmp.service - Update UTMP about System Boot/Shutdown...
         Starting systemd-userdbd.service - User Database Manager...
[  OK  ] Finished systemd-update-utmp.service - Update UTMP about System Boot/Shutdown.
[  OK  ] Finished systemd-journal-catalog-update.service - Rebuild Journal Catalog.
[  OK  ] Started systemd-userdbd.service - User Database Manager.
[  OK  ] Started systemd-oomd.service - Userspace Out-Of-Memory (OOM) Killer.
[  OK  ] Finished systemd-hwdb-update.service - Rebuild Hardware Database.
         Starting systemd-networkd.service - Network Configuration...
         Starting systemd-update-done.service - Update is Completed...
[  OK  ] Finished systemd-update-done.service - Update is Completed.
[  OK  ] Reached target sysinit.target - System Initialization.
[  OK  ] Started dnf-makecache.timer - dnf makecache --timer.
[  OK  ] Started logrotate.timer - Daily rotation of log files.
[  OK  ] Started systemd-tmpfiles-clean.timer - Daily Cleanup of Temporary Directories.
[  OK  ] Reached target timers.target - Timer Units.
[  OK  ] Listening on dbus.socket - D-Bus System Message Bus Socket.
[  OK  ] Reached target sockets.target - Socket Units.
[  OK  ] Reached target basic.target - Basic System.
[  OK  ] Reached target sshd-keygen.target.
         Starting sysstat.service - Resets System Activity Logs...
         Starting systemd-homed.service - Home Area Manager...
         Starting systemd-logind.service - User Login Management...
         Starting dbus-broker.service - D-Bus System Message Bus...
[FAILED] Failed to start sysstat.service - Resets System Activity Logs.
See 'systemctl status sysstat.service' for details.
[  OK  ] Started dbus-broker.service - D-Bus System Message Bus.
[  OK  ] Started systemd-homed.service - Home Area Manager.
[  OK  ] Finished systemd-homed-activate.service - Home Area Activation.
[  OK  ] Started systemd-logind.service - User Login Management.
[  OK  ] Started systemd-networkd.service - Network Configuration.
         Starting systemd-networkd-wait-online.service - Wait for Network to be Configured...
         Starting systemd-resolved.service - Network Name Resolution...
[  OK  ] Started systemd-resolved.service - Network Name Resolution.
[  OK  ] Reached target network.target - Network.
[  OK  ] Reached target nss-lookup.target - Host and Network Name Lookups.
         Starting sshd.service - OpenSSH server daemon...
         Starting systemd-user-sessions.service - Permit User Sessions...
[  OK  ] Finished systemd-user-sessions.service - Permit User Sessions.
[  OK  ] Started console-getty.service - Console Getty.
[  OK  ] Reached target getty.target - Login Prompts.
[  OK  ] Started sshd.service - OpenSSH server daemon.
[  OK  ] Reached target multi-user.target - Multi-User System.
[  OK  ] Reached target graphical.target - Graphical Interface.
         Starting systemd-update-utmp-runlevel.service - Update UTMP about System Runlevel Changes...
[  OK  ] Finished systemd-update-utmp-runlevel.service - Update UTMP about System Runlevel Changes.

Fedora 35 (Rawhide Prerelease)
Kernel 5.12.12-300.fc34.x86_64 on an x86_64 (console)

rawhide login: [  OK  ] Stopped session-24.scope - Session 24 of User zbyszek.
[  OK  ] Removed slice system-getty.slice - Slice /system/getty.
[  OK  ] Removed slice system-modprobe.slice - Slice /system/modprobe.
[  OK  ] Removed slice system-sshd\x2dkeygen.slice - Slice /system/sshd-keygen.
[  OK  ] Stopped target graphical.target - Graphical Interface.
[  OK  ] Stopped target multi-user.target - Multi-User System.
[  OK  ] Stopped target getty.target - Login Prompts.
[  OK  ] Stopped target machines.target - Containers.
[  OK  ] Stopped target nss-lookup.target - Host and Network Name Lookups.
[  OK  ] Stopped target remote-cryptsetup.target - Remote Encrypted Volumes.
[  OK  ] Stopped target timers.target - Timer Units.
[  OK  ] Stopped dnf-makecache.timer - dnf makecache --timer.
[  OK  ] Stopped logrotate.timer - Daily rotation of log files.
[  OK  ] Stopped systemd-tmpfiles-clean.timer - Daily Cleanup of Temporary Directories.
[  OK  ] Closed systemd-coredump.socket - Process Core Dump Socket.
         Stopping console-getty.service - Console Getty...
         Stopping dracut-shutdown.service - Restore /run/initramfs on shutdown...
         Stopping sshd.service - OpenSSH server daemon...
         Stopping systemd-logind.service - User Login Management...
         Stopping systemd-oomd.service - Userspace Out-Of-Memory (OOM) Killer...
         Stopping user@1000.service - User Manager for UID 1000...
[  OK  ] Stopped systemd-oomd.service - Userspace Out-Of-Memory (OOM) Killer.
[  OK  ] Stopped systemd-networkd-wait-online.service - Wait for Network to be Configured.
[  OK  ] Stopped sshd.service - OpenSSH server daemon.
[  OK  ] Stopped console-getty.service - Console Getty.
[  OK  ] Stopped dracut-shutdown.service - Restore /run/initramfs on shutdown.
[  OK  ] Stopped target sshd-keygen.target.
[  OK  ] Stopped systemd-logind.service - User Login Management.
[  OK  ] Stopped user@1000.service - User Manager for UID 1000.
         Stopping user-runtime-dir@1000.service - User Runtime Directory /run/user/1000...
[  OK  ] Unmounted run-user-1000.mount - /run/user/1000.
[  OK  ] Stopped user-runtime-dir@1000.service - User Runtime Directory /run/user/1000.
[  OK  ] Removed slice user-1000.slice - User Slice of UID 1000.
         Stopping systemd-user-sessions.service - Permit User Sessions...
[  OK  ] Stopped systemd-user-sessions.service - Permit User Sessions.
[  OK  ] Stopped target network.target - Network.
[  OK  ] Stopped target remote-fs.target - Remote File Systems.
         Stopping systemd-homed-activate.service - Home Area Activation...
         Stopping systemd-resolved.service - Network Name Resolution...
[  OK  ] Stopped systemd-resolved.service - Network Name Resolution.
         Stopping systemd-networkd.service - Network Configuration...
[  OK  ] Stopped systemd-homed-activate.service - Home Area Activation.
         Stopping systemd-homed.service - Home Area Manager...
[  OK  ] Stopped systemd-homed.service - Home Area Manager.
[  OK  ] Stopped target basic.target - Basic System.
[  OK  ] Stopped target paths.target - Path Units.
[  OK  ] Stopped target slices.target - Slice Units.
[  OK  ] Removed slice user.slice - User and Session Slice.
[  OK  ] Stopped target sockets.target - Socket Units.
         Stopping dbus-broker.service - D-Bus System Message Bus...
[  OK  ] Stopped dbus-broker.service - D-Bus System Message Bus.
[  OK  ] Closed dbus.socket - D-Bus System Message Bus Socket.
[  OK  ] Stopped target sysinit.target - System Initialization.
[  OK  ] Stopped target cryptsetup.target - Local Encrypted Volumes.
[  OK  ] Stopped systemd-ask-password-console.path - Dispatch Password Requests to Console Directory Watch.
[  OK  ] Stopped systemd-ask-password-wall.path - Forward Password Requests to Wall Directory Watch.
[  OK  ] Stopped target veritysetup.target - Local Verity Integrity Protected Volumes.
[  OK  ] Stopped systemd-update-done.service - Update is Completed.
[  OK  ] Stopped ldconfig.service - Rebuild Dynamic Linker Cache.
[  OK  ] Stopped systemd-hwdb-update.service - Rebuild Hardware Database.
[  OK  ] Stopped systemd-journal-catalog-update.service - Rebuild Journal Catalog.
         Stopping systemd-update-utmp.service - Update UTMP about System Boot/Shutdown...
[  OK  ] Stopped systemd-networkd.service - Network Configuration.
[  OK  ] Closed systemd-networkd.socket - Network Service Netlink Socket.
[  OK  ] Stopped systemd-sysctl.service - Apply Kernel Variables.
[  OK  ] Stopped systemd-update-utmp.service - Update UTMP about System Boot/Shutdown.
[  OK  ] Stopped systemd-tmpfiles-setup.service - Create Volatile Files and Directories.
[  OK  ] Stopped target local-fs.target - Local File Systems.
         Unmounting home.mount - /home...
         Unmounting run-credentials-systemd\x2dsysusers.se…e.mount - /run/credentials/systemd-sysusers.service...
         Unmounting tmp.mount - Temporary Directory /tmp...
[  OK  ] Unmounted home.mount - /home.
[  OK  ] Unmounted tmp.mount - Temporary Directory /tmp.
[  OK  ] Unmounted run-credentials-systemd\x2dsysusers.service.mount - /run/credentials/systemd-sysusers.service.
[  OK  ] Stopped target local-fs-pre.target - Preparation for Local File Systems.
[  OK  ] Stopped target swap.target - Swaps.
[  OK  ] Reached target umount.target - Unmount All Filesystems.
[  OK  ] Stopped systemd-tmpfiles-setup-dev.service - Create Static Device Nodes in /dev.
[  OK  ] Stopped systemd-sysusers.service - Create System Users.
[  OK  ] Stopped systemd-remount-fs.service - Remount Root and Kernel File Systems.
[  OK  ] Reached target shutdown.target - System Shutdown.
[  OK  ] Reached target final.target - Late Boot Services.
[  OK  ] Finished systemd-poweroff.service - System Power Off.
[  OK  ] Reached target poweroff.target - System Power Off.
Sending SIGTERM to remaining processes...
Sending SIGKILL to remaining processes...
All filesystems, swaps, loop devices, MD devices and DM devices detached.
Powering off.

1 files changed, 10 insertions, 11 deletions

diff --git a/man/systemd.unit.xml b/man/systemd.unit.xml
index 78ba9731dd..7fafbc1d4c 100644
--- a/man/systemd.unit.xml
+++ b/man/systemd.unit.xml
@@ -561,20 +561,19 @@
     <variablelist class='unit-directives'>
       <varlistentry>
         <term><varname>Description=</varname></term>
-        <listitem><para>A human readable name for the unit. This is used by
-        <command>systemd</command> (and other UIs) as the label for the unit, so this string should
-        identify the unit rather than describe it, despite the name. <literal>Apache2 Web
-        Server</literal> is a good example. Bad examples are <literal>high-performance light-weight
-        HTTP server</literal> (too generic) or <literal>Apache2</literal> (too specific and
-        meaningless for people who do not know Apache). <command>systemd</command> will use this
-        string as a noun in status messages (<literal>Starting
+        <listitem><para>A short human readable title of the unit. This may be used by
+        <command>systemd</command> (and other UIs) as a user-visible label for the unit, so this string
+        should identify the unit rather than describe it, despite the name. This string also shouldn't just
+        repeat the unit name. <literal>Apache2 Web Server</literal> is a good example. Bad examples are
+        <literal>high-performance light-weight HTTP server</literal> (too generic) or
+        <literal>Apache2</literal> (meaningless for people who do not know Apache, duplicates the unit
+        name). <command>systemd</command> may use this string as a noun in status messages (<literal>Starting
         <replaceable>description</replaceable>...</literal>, <literal>Started
         <replaceable>description</replaceable>.</literal>, <literal>Reached target
         <replaceable>description</replaceable>.</literal>, <literal>Failed to start
-        <replaceable>description</replaceable>.</literal>), so it should be capitalized, and should
-        not be a full sentence or a phrase with a continuous verb. Bad examples include
-        <literal>exiting the container</literal> or <literal>updating the database once per
-        day.</literal>.</para>
+        <replaceable>description</replaceable>.</literal>), so it should be capitalized, and should not be a
+        full sentence, or a phrase with a continuous verb. Bad examples include <literal>exiting the
+        container</literal> or <literal>updating the database once per day.</literal>.</para>
         </listitem>
       </varlistentry>