Google tells me it should be ok to backup ext4 “/” or subdirs to a FAT32 partition. Its not for me but i would like to tell a friend of mine ( not computer interested but using Mint ) how to backup to new external disk, thats probably FAT32 formatted.
My BackIntIme backups are on ext4 partition and i see a file there called “fileinfo” that seems to have all the file attributes saved.
Example line in file fileinfo:
32813 root root /var/lib/NetworkManager/secret_key
No, backintime should not be used for storing backups on a FAT, FAT-derivative or NTFS filesystem, because it uses rsync in the background, which needs to be able to create hard-links for files that haven’t changed since the last backup, and those filesystems do not support that.
In addition to that, as @Keruskerfuerst said, those filesystems do not support POSIX permissions and file ownership.