Moving from GNU tar version 1.15.1 to 1.20 causes a level 0 dump. I searched the manual and the mailing list archives, but I found no mention of this.
The online manual (http://www.gnu.org/software/tar/manual/tar.html#SEC172) states "GNU tar version 1.22 supports three snapshot file formats": format 0, format 1, and its native format, format 2. However, when I feed a snapshot file made with version 1.15.1 GNU tar (capable only of level 0 snapshot files) to 1.20 GNU tar, it routinely overwrites the snapshot file with the level 2 version and populates the new tar file with all data, not just what has changed. Here are the commands I used on some test directories and their result: # /bin/tar --version tar (GNU tar) 1.15.1 # /bin/tar --create --file=./foo.1.tar --listed-incremental=./foo.snap ./Binaries # /bin/tar --create --file=./foo.2.tar --listed-incremental=./foo.snap ./Binaries # /bin/tar --create --file=./foo.3.tar --listed-incremental=./foo.snap ./Binaries/ ./backup-progs # strings foo.snap | head GNU tar-1.22-2 1263621813 180228000 1241196232 2049 9899855 ./Binaries/areca/archttpsrv/V1.82_70911/x86-64 Yarchttp64 Yarchttp64.log Yarchttpsrv.conf # ls -ltrh foo* -rw-r--r-- 1 root root 34M Jan 16 00:59 foo.1.tar -rw-r--r-- 1 root root 40K Jan 16 01:01 foo.2.tar -rw-r--r-- 1 root root 130K Jan 16 01:02 foo.3.tar -rw-r--r-- 1 root root 6.5K Jan 16 01:03 foo.snap -rw-r--r-- 1 root root 55M Jan 16 01:03 foo.4.tar # du -sh Binaries/ backup-progs/ files-count/ 34M Binaries/ 240K backup-progs/ 22M files-count/ -Erik
