Am 2014-11-20 um 11:17 schrieb Goffredo Baroncelli:
On 2014-11-19 23:48, Jakob Schürz wrote:
Hi there!
Another challenge... I'm using btrfs. So i make snapshots from my
system. And in a script, I make a symlink (for example:
@system.CURRENT and @system.LAST) for the current and the last
snapshot.
Interesting, I was unaware that I could mount a subvolume passing
a "soft" link.
Fortunately Yes, that works. :)
So i came on this idea, to create 2 (or more) stable links on the
current, last and so on snapshot. The Problem is the fstab...
So i want to add 2 entries in grub2 from which i can boot into the
current and the last snapshot.
I tried to pass an environmental variable with
systemd.setenv=BOOTSNAP=@system.CURRENT, and i have a mount-unit
containing the option
Options=defaults,nofail,subvol=archive-local/@system.$BOOTSNAP
but it doesn't work. If i change $BOOTSNAP to CURRENT, the mount
works. So i made a test.service, containing only StartExec=/bin/echo
$BOOTSNAP I get the value @system.CURRENT in the logs...
This is more a systemd related question. However it seems that ExecStart
supports "...basic environment variable substitution..."; but the mount unit
doesn't. This explain your difficulties. Anyway I suggest you to contact the
systemd developers to get further support; maybe that this could be a add as
TODO item.
I hope so... and i found out, that this is not a btrfs-challenge.
On the grub-devel-list i saw a discussion to make dynamically entries
for all snapshots in a certain directory according to this challenge.
But this also didn't solve the fstab-challenge.
So i think i have to place it on a systemd-devel-list...
How can I do this mounts?
For the boot, I used the "rootflags=" command line options. This
usually is interpreted by the initrd/initramfs as option to pass
to the mount command. In my case I have:
rootflags=subvol=debian
so, the subvol=debian option is passed to mount. When grub-mkconfig
generates the grub menu entries, does so.
This I also have in my grub-config, and it works. But it doesn't solve
the challenge. Mounting more subvolumes according to the
root-subvolume... :-)
regards
Jakob
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
