Linux – How to backup a running system

backupddlinux

I have a running Linux system, and I'd like to have a full backup of it using dd, which, in my limited knowledge is the only tool every system has.

The distro doesn't matter mainly because I should apply this approach to several different servers with different flavours installed, and I cannot install new software on these servers.

What is the most generic and efficient way to complete such task?

Best Answer

Not so much a solution as a few nuggets of advice which may be helpful to consider if using tar/cpio/rsync etc. First, it might be a good idea to backup from a bind mount of your source filesystem (mount --bind source mntdir). This will have a similar effect as the --one-file-system options to rsync and tar and -xdev with find. It has the advantages of working if these options are unavailable (perhaps due to an old version, although note that bind mounts were introduced in Linux 2.4) and allowing files underneath mount points to be backed up, which may be desirable in some cases.

Second, I would advise to use numeric uids and gids where possible (--numeric-owner for tar, --numeric-ids for rsync and --numeric-uid-gid for cpio). If you restore a backup without this and an owner/group no longer exists or the uid/gid is different (this may happen particularly if a live disc is used to restore the backup), you can have one set of uids/gids used when restoring which become invalid after /etc/passwd and /etc/group are restored.

Also, take a look at clonezilla. The methods that they use to do the bulk of the backup may not be of use to you, but when it runs has options to backup boot sectors/partition tables and supports both MBR and GPT, so there may be some scripts there which can be copied/adapted to your purposes.

As a final 2 cents, I would consider rsync to be the standard way to do this. It is surely the most efficient method when doing incremental backups, although not so much for a one off full backup. Sure, it is not ubiquitous, but I think it is a mistake not to include it in the server edition of a distro. It may well already be installed on all of your servers.

Related Solutions

Linux – How to measure and prevent clock drift

Are there tools which measure time of day clock drift?

The only tools I'm aware of are the NTP tools which should suffice. You don't have to actually configure ntpd to sync against a given clock source you can just use the -d option to ntpdate to fetch the calculated offset.

Example:

[davisja5@xxxadmvlm08 ~]$ ntpdate -d clock.redhat.com 2>/dev/null | egrep "^offset"
offset -0.004545
[davisja5@xxxadmvlm08 ~]$

-d is the debug option which does the NTP work without actually touching the system clock.

Any advice on how we can avoid this?

I'm not too surprised that you aren't able to reproduce this in dev/test environments since it's probably just due to the hardware clock. If you have hardware support with someone, I would try to get your machines serviced. One possibility is trading out one of the dev machines for this production machine, fixing the former PROD systems and re-introduce it as a dev machine to replace the one that's in PROD now.

Short of that, switching the hardware clock source is about all you can do. If you don't or can't do the swap thing I'd suggest that you do go the hpet route. You can test whether the clock source change messes with system services and then deploy it into production as a hail mary.

Debian – how to do version-specific backup/restore of Debian packages

Some useful notes to help you achieve your goal:

You can get a list of installed packages and their versions by running:

dpkg-query -W

You can create an archive of .deb packages of all currently installed packages by installing dpkg-repack and running something like this:

dpkg-query -W | awk '{print $1}' | xargs dpkg-repack

This will dpkg-repack all currently installed packages. This archive is the crucial missing part to your restore - without it, you may not be able to restore the exact same package set (especially if you use testing or unstable).

WARNING: dpkg-repack repacks the current, possibly modified, contents of all conffiles. If you want the pristine, original packages, you'll have to get the .deb files from /var/cache/apt/archives or from a Debian mirror.

The .deb archive can be turned into an apt-gettable repository by following the instructions at https://wiki.debian.org/HowToSetupADebianRepository or you can just install them all with dpkg -iBE *.deb (or dpkg -iRBE /path/to/deb/files/ if there are too many to fit on one command line).

You'll still need to use -get-selections and --set-selections in order to retain details like de-installed packages.

Best Answer

Related Solutions

Linux – How to measure and prevent clock drift

Debian – how to do version-specific backup/restore of Debian packages

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