Why do Tree Blobs change without file changes?

I run restic backup with “–dry-run” to check if any changes occured and only if there are changes I run restic backup (I do this to avoid having really long lists of snapshots that are identical, this way i can see when changes occured by looking at the snapshot dates). However, last night a backup did run, even so no files changed with this output:

comparing snapshot d97c616d to fd1729f7:

Files:           0 new,     0 removed,     0 changed
Dirs:            0 new,     0 removed
Others:          0 new,     0 removed
Data Blobs:      0 new,     0 removed
Tree Blobs:      2 new,     2 removed
  Added:   730 B
  Removed: 730 B

Can someone explain what happened here or what would be a better approach to achieve the desired outcome?
Thank you!

There are “artificial” tree objects created to make a full tree starting at root. E.g. when you backup “/home/user”, the “home” and “user” tree is generated.

IIRC, restic sets the current timestamp as modification date for these artifical trees, i.e. they are always changing.

1 Like

The timestamp and other properties of these root folders are based on the actual folders.

Ok, then I was wrong. What could be another explanation of the behavior @vdecine observed?

My guess would be that some update caused some of these folders to change. At least judging from my system e.g. the modification timestamp of / changes from time to time.