Setting mount option `sync` for root parition in fstab causes umount to fail during shutdown

[lennart@xxxxxxxxxxxxxx (Lennart Poettering)]

On Mi, 08.08.18 17:17, Isaac Nickaein (nickaein.i at gmail.com) wrote:

> On Wed, Aug 8, 2018 at 1:16 PM Lennart Poettering
> <lennart at poettering.net> wrote:
> >
> > > systemd-shutdown[1]: Unmounting file systems.
> > > systemd-shutdown[1]: Remounting '/' read-only with options 'sync,data=ordered'.
> > > EXT4-fs (mmcblk2p1): Unrecognized mount option "sync" or missing value
> > > systemd-shutdown[1]: Remounting '/' read-only with options 'sync,data=ordered'.
> > > EXT4-fs (mmcblk2p1): Unrecognized mount option "sync" or missing value
> >
> > This message is generated by the kernel. This appears to be a kernel
> > problem: it apparently doesn't allow remounts of ext4 if we specify
> > "sync" in the mount options...
> >
> > Please report this to the kernel folks.
> 
> OK, I will try my chances. However, there seems to be a fundamental
> issue with filesystem-independent flags like `sync` as discussed here:
> https://unix.stackexchange.com/a/131414/91614

Ah right, I missed that MS_SYNC is actually one of the low-level
flags, not the normal mount options.

So in that case, which systemd version are you running?

I figure 3bc341bee9fc7dfb41a131246b6fb0afd6ff4407 should fix your
issue. Does your version include that already?

Lennart

-- 
Lennart Poettering, Red Hat