Am 19.01.2023 20:14, schrieb Charles Curley:
On Thu, 19 Jan 2023 12:49:57 -0600
Tom Browder <tom.brow...@gmail.com> wrote:
+ Can it do a complete clone on an active disk? Or do I need a live
CD or USB stick?
I wouldn't try backing up a live partition due to issues with
referential integrity. Suppose two interdependent files, A and B,
change
during the backing up, like so:
A is backed up.
A and B are both changed.
B is backed up.
Your originals are fine, they both have the changes. But the backup is
broken: only one file has the changes.
That's true. Especially for a block based copy of mounted filesystems
there's a high risk of inconsistency, which results not only in broken
files but even not mountable filesystems. (i.e. something like a "dd" of
the /dev/sdX)
Copying files from some mounted filesystem, even some active root
partition, works for most cases. It's not exactly 100%, but there's a
high chance everything is fine. I did that several times right in the
live system and never got real problems. Even including databases
(SQL+ldap). Yes, it's absolutely preferred to boot the machine by some
external boot media for system cloning purposes, but if someone wants to
take the risk, chances are high it works.
It's reliable enough so that many backup solutions don't depend on
snapshots. And it works. Yet, backing up data _with_ using snapshots is
to be preferred.
The only exception to that is an LVM logical disk (or similar) where
you
have taken a snapshot, and you back up the snapshot.
or any other snapshot mechanism like btrfs snapshots.
hede
