Back In Time

No incremental backup

Asked by Jörg Arndt

Hi I'm using BIT with Xubuntu 13.10.
The source-data is on a HDD formated with ntfs. The backups are on another internal disk .
BIT takes everytime a complete Snapshote.
I read that this may depend on the filesystem, so I reformated the targed HDD with ext4, but I get still the same problem. What else could I do?

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Germar (germar) said : 		#1

Sorry for putting a question mark on it. But why do you think they are not incremental?

Can you please compare the inodes of a file that definitely didn't change between two snapshots? For this open two Terminals and 'cd' into both snapshot folder. 'ls -lai' will print a list where the first column is the inode which should be equal for the same file in both snapshots if the file didn't change and the snapshots are incremental. The third column is a counter (if the file is no directory) on how many hard-links exist for this inode. It should be >1. So if you took e.g. 3 snapshots it should be 3.

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Jörg Arndt (noebian) said : 		#2

I think that is not indremental because every snapshot has more than 90 GB. I start BIT every day. There a hundreds of files among which are definitely not changed. Is this anyhow useful to compare the inodes? Than will I do it.

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Germar (germar) said : 		#3

Comparing the inodes is the only way to reliable tell if it is incremental. You just need to do this for one file. So no big deal.

If you only right-click on properties in your favourite file-manager and look at the size of every single snapshot you will always see 90GB. Even if it is incremental because every snapshot contain a full set of all files where those that didn't change are hard-links. You can install 'apt-get install ncdu' and run 'ncdu' inside the backintime-folder. This will calculate the size of the snapshots with respect on the hard-linking.

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Jörg Arndt (noebian) said : 		#4

Thank you for the advice!
ncdu calculates also > 90GB
ls -lai shows the same numbers in each snapshot. Both inode and counter.

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Best Germar (germar) said : 		#5

So it is incremental!
Sorry, maybe I wasn't clear enough. Please run ncdu inside the folder where all snapshots are. e.g. /mnt/disk/backintime/HOST/USER/1/
This will show you that only one snapshot has 90GB (the one that ncdu processes at first, that can be different to the real first snapshot, so don't be confused) and all other just a few MB.

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Jörg Arndt (noebian) said : 		#6

Thanks Germar, that solved my question.