Support using flatpak's history command on systemdless systems

[saltedcoffii]

Linux distribution and version

Alpine Linux Edge

Flatpak version

Flatpak 1.10.2

Description of the problem

Flatpak's history command requires libsystemd, however libsystemd isn't available on systems without systemd such as Void, Alpine, some Gentoo, ChromiumOS, etc. Is it possible to use libelogind instead?

[refi64]

This relies on journald, so no I don't believe libelogind would work in its place.

[saltedcoffii]

Maybe there's another way to do this with a different system logging daemon, or a flatpak logging daemon? If it's too much work, devs are more than welcome to close this though.

[smcv]

As @refi64 said, elogind is a replacement for systemd-logind (only), but this information is coming from systemd-journald, not from systemd-logind, so elogind is not a suitable replacement. Because the Journal is outside elogind's scope, libelogind's implementation of sd_journal_open() is a stub that just fails with ENOSYS, so if you compiled flatpak-history(1) against libelogind, you'd still get an error message and no history. This doesn't seem worth doing just to get a different error message :-)

Maybe there's another way to do this with a different system logging daemon, or a flatpak logging daemon?

I suspect none of the Flatpak maintainers have any interest in writing this code. If you want it to happen, someone who wants it would have to write it and send a pull request (which would not necessarily be merged, depending on how much code it ended up being).

If you choose not to use systemd, then there's a price you pay for that, which is that features that rely on the facilities it provides will not be available to you.

[saltedcoffii]

Unfortunately it's not my choice, I'm working on fully porting flatpak to work natively on ChromeOS, which does not use systemd and ChromeOS's init system (upstart) cannot be easily replaced with systemd by any means. Thank you though.

I'm using Alpine to see how flatpak runs on a non-systemd system with Alpine, as upstart cannot be found on any other modern Linux distributions.

[refi64]

Doesn't Chrome OS have a board config using systemd...Latiku it's called I think?

[saltedcoffii]

The binary downloading website doesn't look like it has a board config named that. It looks like there's a bug that denotes some progress with ChromeOS supporting systemd, however it isn't implemented in any chromebooks currently (as far as I know). It's really not a big deal if flatpak devs can't pick this up.

[smcv]

I'm working on fully porting flatpak to work natively on ChromeOS

If ChromeOS has a logging framework in which unprivileged user programs can write and read back their own log messages, analogous to what Flatpak does with systemd-journald right now, then I suspect that a pull request teaching flatpak history to read from that, and teaching FlatpakDir to write to it, would be a lot better-received than inventing a new logging mechanism solely for Flatpak.

[smcv]

I think the feature request as stated here is too broad, so I'm labelling this as wontfix: we're not going to implement our own logging framework just to be able to say we have it.

If users of non-systemd systems want to contribute support for a specific non-systemd-linked logging framework as an alternative to systemd-journald - "Support using flatpak's history command on systems that use foobarlogd instead of systemd-journald" or something - then that's a much more reasonable scope. I think the features that are needed from the logging framework would be something like this:

1. Applications can write out messages to the log
2. Applications can read back at least their own messages from the log (but not necessarily other users' messages)
3. Applications can put machine-readable information in the log message (it's not just an arbitrary human-readable string)

A traditional Unix syslog implementation has (1), and has (2) if you're in the privileged group that can read the log (adm on Debian, might vary on other OSs), but does not have (3).