[gentoo-user] How to replay a backup system?

[Helmut Jarausch]

Hi,
from time to time - as was the case a few days ago - Gentoo updates
lead to an unbootable system.
I backup my system each day - using BTRFS snapshots.

Now, only a few files on current system have changed; the rest of the
400 GB root partition is unchanged.
Therefore I only have to replace these newer files by the versions
saved a day before.

How can this be done efficiently? Unfortunately AFAIK rsync doesn't
have an option to copy only files which are
NEWER on the destination than the corresponding files in the backup.

Many thanks for a hint,
Helmut

[Neil Bothwick]

Post by Helmut Jarausch
from time to time - as was the case a few days ago - Gentoo updates
lead to an unbootable system.
I backup my system each day - using BTRFS snapshots.
Now, only a few files on current system have changed; the rest of the
400 GB root partition is unchanged.
Therefore I only have to replace these newer files by the versions
saved a day before.
How can this be done efficiently? Unfortunately AFAIK rsync doesn't
have an option to copy only files which are
NEWER on the destination than the corresponding files in the backup.

You can replace the original root subvolume with the snapshot. One way of
doiing it is detailed at
https://unix.stackexchange.com/questions/19211/how-to-create-a-snapshot-in-btrfs-and-then-rollback-to-it-after-some-work

[Helmut Jarausch]

Post by Neil Bothwick

Post by Helmut Jarausch
from time to time - as was the case a few days ago - Gentoo updates
lead to an unbootable system.
I backup my system each day - using BTRFS snapshots.
Now, only a few files on current system have changed; the rest of

the

Post by Helmut Jarausch
400 GB root partition is unchanged.
Therefore I only have to replace these newer files by the versions
saved a day before.
How can this be done efficiently? Unfortunately AFAIK rsync doesn't
have an option to copy only files which are
NEWER on the destination than the corresponding files in the backup.

You can replace the original root subvolume with the snapshot. One way of
doiing it is detailed at
https://unix.stackexchange.com/questions/19211/how-to-create-a-snapshot-in-btrfs-and-then-rollback-to-it-after-some-work

Thanks Neil,

unfortunately my root FS is of type ext4, only my backup FS is of type
BTRFS

Helmut