[systemd-devel] How to implement fsck progress report with systemd and plymouth?

[Lennart Poettering]

On Fri, 22.04.11 15:04, fykcee1 at gmail.com (fykcee1 at gmail.com) wrote:

> Hi all,
> 
> plymouth in Ubuntu 10.04 supports fsck progress report, and also
> provides a chance for user to cancel running fsck. How to implement
> this feature with systemd and plymouth?

It's actually a really hard problem. For example, what do you do when
you have multiple disks which are fsck'ed in parallel or serial? You'd
then have to integrate their individual progress bars somehow.

> I did some investigation, found:
> 1. ubuntu patches on_update() of plymouth/src/main.c, it will filter
> out status message from fsck, if message starts with "fsck:".
> 2. ubuntu provides a plymouth theme -- ubuntu-logo, which is of type
> script, and has some fsck related stuff.
> 
> I guess we need:
> 1. Support "detailed status report" in plymouth, e.g. colon separated
> fields.
> 2. Hook fsck detailed message to each theme in plymouth ?
> 3. Emit fsck message to plymouth in systemd-fsck.
> 4. How to support user-cancellable fsck?

> Any idea?

Here's what I'd suggest: We already have systemd-fsck, which we could
beef up slightly to pass progress data to a tiny AF_UNIX socket
activated service (let's call it fsckd) which integrates the data from
multiple instances of systemd-fsck and sends it off to plymouth. And if
a cancel request is received from plymouth it would send off SIGINT to
the the systemd-fsck instances which it got data from.

This could be done in a relative easy and elegant way by having
systemd-fsck just pass the socket it created as channel to fsckd as -C
fd to to fsck. That way only fsckd would have to parse the progress data
from fsck, and it would talk directly to fsck which would allow fsckd to
figure out the fsck PID via SCM_CREDENTIALS, so that fsckd would know
what to kill.

Lennart

-- 
Lennart Poettering - Red Hat, Inc.