On 2016-05-06 07:48, Niccolò Belli wrote:
The following are my subvolumes:
$ sudo btrfs subvol list /
[sudo] password di niko: ID 257 gen 1040 top level 5 path @
ID 258 gen 1040 top level 5 path @home
ID 270 gen 889 top level 257 path var/cache/pacman/pkg
ID 271 gen 15 top level 257 path var/abs
ID 272 gen 972 top level 257 path var/tmp
ID 273 gen 37 top level 257 path tmp
ID 274 gen 20 top level 257 path srv
ID 276 gen 25 top level 258 path @home/niko/.cache/pacaur
ID 280 gen 993 top level 257 path .snapshots
ID 281 gen 993 top level 258 path @home/.snapshots
ID 282 gen 169 top level 280 path .snapshots/1/snapshot
ID 283 gen 171 top level 280 path .snapshots/2/snapshot
ID 284 gen 173 top level 280 path .snapshots/3/snapshot
ID 285 gen 124 top level 281 path @home/.snapshots/1/snapshot
ID 286 gen 175 top level 280 path .snapshots/4/snapshot
ID 288 gen 177 top level 280 path .snapshots/5/snapshot
ID 290 gen 237 top level 280 path .snapshots/6/snapshot
ID 291 gen 238 top level 281 path @home/.snapshots/2/snapshot
ID 292 gen 308 top level 280 path .snapshots/7/snapshot
ID 293 gen 309 top level 281 path @home/.snapshots/3/snapshot
ID 294 gen 376 top level 280 path .snapshots/8/snapshot
ID 295 gen 377 top level 281 path
@home/.snapshots/4/snapshot
ID 296 gen 442 top level
280 path .snapshots/9/snapshot
ID 297 gen 443 top level
281 path @home/.snapshots/5/snapshot
ID 298 gen 511 top level
280 path .snapshots/10/snapshot
ID 299 gen 512 top level
281 path @home/.snapshots/6/snapshot
ID 300 gen 578 top level
280 path .snapshots/11/snapshot
ID 301 gen 579 top level
281 path @home/.snapshots/7/snapshot
ID 302 gen 648 top level
280 path .snapshots/12/snapshot
ID 303 gen 649 top level
281 path @home/.snapshots/8/snapshot
ID 304 gen 716 top level
280 path .snapshots/13/snapshot
ID 305 gen 717 top level
281 path @home/.snapshots/9/snapshot
ID 306 gen 967 top level
280 path .snapshots/14/snapshot
ID 307 gen 789 top level
281 path @home/.snapshots/10/snapshot
ID 309 gen 834 top level
280 path .snapshots/15/snapshot
ID 310 gen 874 top level
280 path .snapshots/16/snapshot
ID 311 gen 875 top level
281 path @home/.snapshots/11/snapshot
ID 312 gen 887 top level
280 path .snapshots/17/snapshot
ID 313 gen 888 top level 280 path
.snapshots/18/snapshot
ID 314 gen 904 top level 280 path
.snapshots/19/snapshot
ID 316 gen 938 top level 280 path
.snapshots/20/snapshot
ID 317 gen 939 top level 281 path
@home/.snapshots/12/snapshot
ID 318 gen 991 top level 280 path
.snapshots/21/snapshot
ID 319 gen 992 top level 281 path
@home/.snapshots/13/snapshot
I would like to rollback to .snapshots/14/snapshot, restoring my @
subvolume to such a previous state.
So I booted into a livecd, mounted my disk into /mnt and typed:
btrfs subvol snapshot /mnt/@/.snapshots/14/snapshot /mnt/@
Unfortunately it simply creates a new /mnt/@/snapshot subvolume instead
of replacing @.
If @ didn't have any nested subvolume I would simply delete it and run
the previous command again, but
1) I dont't want to lose the @ nested subvolumes like var/cache/pacman/pkg
2) btrfs subvolume delete /mnt/@ doesn't want to delete it (cannot
delete directory not empty), probably because of the nested subvolumes
So, how am I supposed to rollback to a previous snapshot?
General procedure:
1. Rename the subvolume you want to replace to something else.
2. run the command you had used above.
3. Remove the empty directories in the new subvolume that result from
the nested snapshots/subvolumes.
4. Snapshot all the nested subvolumes from the old subvolume into the
required locations in the new one.
5. If you're running off of the subvolume you're replacing, reboot
(completely, not just drop to single user or emergency mode or
whatever), if not (for example, if you're using a live-CD, just continue
to the next step.
6. Delete the old subvolume (you'll have to delete any nested subvolumes
first). This can be deferred to whatever point in time you determine
that you don't need any of the data from it.
Now, as to a slightly higher level discussion, this is part of why usage
of nested subvolumes is generally considered a bad practice. In
general, the only valid use for nested subvolumes is to exclude things
from snapshots.
Part of what you have listed (/var/cache/pacman/pkg, /var/tmp, and /tmp)
is stuff that makes some sense to use like this, as it's all data that
you don't want to snapshot, and it's trivially reproducible. I have a
couple of cases where I'm using nested subvolumes like this to exclude
data that is trivial to reproduce from snapshots (and by extension, from
backups), but I also just drop them and create new ones when I have to
roll-back.
--
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
