[systemd-devel] Second (erroneous) check of rootfs?

[Dave Reisner]

On Sun, Jan 11, 2015 at 10:09:08AM +0300, Andrei Borzenkov wrote:
> В Sat, 10 Jan 2015 16:51:24 +0300
> Nikolai Zhubr <n-a-zhubr at yandex.ru> пишет:
> 
> > Hi,
> > 09.01.2015 23:48, Chris Murphy:
> > [...]
> > >> I might be missing something, but what's wrong with the existing "root=...
> > >> rootfstype=... rootflags=... rw" options? Why is the remount even necessary?
> > >
> > > Seems to be distro specific. I see rw for opensuse or Ubuntu, and ro for Fedora.
> > >
> > > The ro seems antiquated to me, meant for interactive fsck on an ro
> > > mounted filesystem when booting single user. 'btrfs check' refuses to
> > > run on mounted file systems, even if ro. And xfs_repair requires the
> > > use of -d "repair dangerously" to do so.
> > >
> > > Both XFS and Btrfs have placeholder fsck's, if you man fsck.xfs or
> > > fsck.btrfs you'll see. These filesystems are designed to fix most
> > 
> > Ok. I've invented a quick-and-dirty fix. I'll modify systemd-fsck so 
> > that when run with no argument it does nothing and exit successfully. 
> > This way I'll still have rootfs fsck'ed every boot, but never twice.
> > 
> 
> Uh. Why not simply mount rootfs rw in initrd then?
> 
> > I'll soon need this box for work anyway, reverting to some 12.x does not 
> > seem very attractive, and living with this bug every day won't give me a 
> > good feeling either. (Just a week ago I had one single erroneous fsck 
> > rendering my rootfs essentially to a complete trash)
> > 
> > Hope someone will come up with a better solution though :)
> 
> The more I think about it the more I find it non-issue. As was already
> mentioned, systemd-fsck checks whether rootfs is mounted read-write and
> will skip check in this case. Could someone give a compelling reason why
> initrd would want to mount rootfs read-only after having fsck'ed it?
> 
> Otherwise the only way to prevent second fsck is to pass some flag from
> initrd to real root, like /run/systemd/fsck-root-done. There is no

This flag file used to exist (though differently named). As soon as
dracut started using systemd, the flag file was deemed unnecessary for
everyone. See commit 956eaf2b8d6 for its removal. See /dev/null for the
discussion which took place before removing it.

> feasible way to reuse the same systemd-fsck-root.service without
> introducing hard dependency on initrd implementation. I hoped to get
> away by just symlinking systemd-fsck-root.service to
> systemd-fsck at root-dev.service, but it's not possible. 
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