[systemd-devel] moving from SysV to systemd - issue with / being ro

[Zbigniew Jędrzejewski-Szmek]

On Wed, Oct 16, 2013 at 06:18:12PM +0200, Warpme wrote:
> Hi,
> I want to switch init system from SysV to systemd-196.
> Sys is PXE booted disk-less appliance with rootfs based on overlayfs.
> 
> Currently I can PXEboot, successfully switch root from initrd to
> overlayfs based root, systemd starts and executes many of it's
> units.
> Unfortunately user units are failing due / is read-only.
> When I issue "mount -o remount,rw /"  - root becomes rw - so it
> looks like systemd for some reason isn't remounting root to rw.
> Interesting is that exactly the same initrd->overlayfs script (see
> below) works OK for SysV - so I think issue isn't in my pivot_root
> procedure but rather systemd receives / in rw but leaves in ro (as
> "mount -o remount,rw /" allows to write to /).
> 
> Script switching initrd to overlayfs root looks following:
> 
> /bin/mount -n -t tmpfs none /rw
> /bin/mkdir -p /rw/rootfs
> /bin/mount -n -t overlayfs -o
> lowerdir=/rootfs-ro,upperdir=/rw/rootfs none /rootfs
> cd /rootfs
> /bin/mkdir -p initrd proc sys
> /sbin/pivot_root . initrd
> exec /usr/sbin/chroot . /usr/lib/systemd/systemd
> 
> Where issue might be?
What's in /etc/fstab?

Zbyszek