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Re: so, systemd now and teh world still turns...

On 03/06/14 20:50, Steven Chamberlain wrote:
> I notice gnome-session-bin recently gained a dependency on systemd libs

Depending on libsystemd-journal0, libsystemd-login0 on Linux doesn't
mean "depends on systemd", only "has some amount of integration with
systemd" (dbus has both dependencies on Linux, and they're inactive when
another init is used, or not compiled at all on non-Linux). Those
libraries do not themselves depend on the daemon.

Depending on libsystemd-login0 but not libpam-systemd means that if
logind happens to be available, the package will use it (e.g. to check
which users are logged in and active), but if not, the package will
continue to work.

Depending on libpam-systemd means the package really doesn't work
without logind, and needs either systemd-sysv (systemd as pid 1) or
systemd-shim. *That* is the significant dependency to add.

Depending on libsystemd-journal0 usually means that if the systemd
journal (machine-readable centralized log) happens to be available, the
package will log additional machine-readable metadata to it, or divert
the stdout/stderr of its child processes to it, or something similar.
dbus-daemon uses that library to direct activated services'
stdout/stderr to the journal, instead of /dev/null where that output has
traditionally gone. By default, the journal does not log anything to
disk on its own, but recent events are held in memory, and the
human-readable subset of its input is passed through to syslog.

gnome-session probably uses the journal for the same reasons as
dbus-daemon: making sure that if run with the journal available, its
child processes' stdout/stderr are logged, and are attributed to the
child process's correct name instead of gnome-session itself.


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