this post was submitted on 17 Jan 2026
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Where to start with backups? (lemmy.world)
submitted 5 months ago by mapleseedfall@lemmy.world to c/selfhosted@lemmy.world
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hi peeps.

Im early on my selfhosting journey and managed to setup some things as a test in docker. the main service im looking to run is ERPNext. after a while I got it up and running so now I want to back this up including all the customization I did in the app.

where to start with this? any intuitive guide?

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[–] tal@lemmy.today 6 points 5 months ago* (last edited 5 months ago)

If databases are involved they usually offer some method of dumping all data to some kind of text file. Usually relying on their binary data is not recommended.

It's not so much text or binary. It's because a normal backup program that just treats a live database file as a file to back up is liable to have the DBMS software write to the database while it's being backed up, resulting in a backed-up file that's a mix of old and new versions, and may be corrupt.

Either:

  1. The DBMS needs to have a way to create a dump

possibly triggered by the backup software, if it's aware of the DBMS

that won't change during the backup

or:

  1. One needs to have filesystem-level support to grab an atomic snapshot (e.g. one takes an atomic snapshot using something like btrfs and then backs up the snapshot rather than the live filesystem). This avoids the issue of the database file changing while the backup runs.

In general, if this is a concern, I'd tend to favor #2 as an option, because it's an all-in-one solution that deals with all of the problems of files changing while being backed up: DBMSes are just a particularly thorny example of that.

Full disclosure: I mostly use ext4 myself, rather than btrfs. But I also don't run live DBMSes.

EDIT: Plus, #2 also provides consistency across different files on the filesystem, though that's usually less-critical. Like, you won't run into a situation where you have software on your computer update File A, then does a sync(), then updates File B, but your backup program grabs the new version of File B but then the old version of File A. Absent help from the filesystem, your backup program won't know where write barriers spanning different files are happening.

In practice, that's not usually a huge issue, since fewer software packages are gonna be impacted by this than write ordering internal to a single file, but it is permissible for a program, under Unix filesystem semantics, to expect that the write order persists there and kerplode if it doesn't...and a traditional backup won't preserve it the way that a backup with help from the filesystem can.