Package: tar
Version: 1.16-2
When I use tar to create incremental archives and combine the
parameters -W (verifying) and -g (incremental backups), the created
snapshot file is incomplete. As a result, the next incremental backup
archives unchanged files.
The following script gives an example ("test" is a subdirectory
containing some files that are unchanged during the entire run of the
script, and there are no archives or snapshot files existing when the
script starts):
-----------
#!/bin/sh
# No verification: good snapshot file
tar -c -v -f good.1.tar -g good.snap test >good.1.log
# Second run: no files are archived
tar -c -v -f good.2.tar -g good.snap test >good.2.log
# Verification: bad snapshot file
tar -c -v -f bad.1.tar -W -g bad.snap test >bad.1.log
# Second run: unchanged files are archived
tar -c -v -f bad.2.tar -W -g bad.snap test >bad.2.log
-----------
These are the log files:
good.1.log:
-----------
test/
test/test/
test/a
test/b
test/c
test/d
test/test/a
test/test/b
test/test/c
test/test/d
-----------
good.2.log:
-----------
test/
test/test/
-----------
bad.1.log:
-----------
test/
test/test/
test/a
test/b
test/c
test/d
test/test/a
test/test/b
test/test/c
test/test/d
Verify test/
Verify test/test/
Verify test/a
Verify test/b
Verify test/c
Verify test/d
Verify test/test/a
Verify test/test/b
Verify test/test/c
Verify test/test/d
-----------
bad.2.log:
-----------
test/
test/test/
test/a
test/b
test/c
test/d
test/test/a
test/test/b
Verify test/
test: Contents differ
Verify test/test/
test/test: Contents differ
Verify test/a
Verify test/b
Verify test/c
Verify test/d
Verify test/test/a
Verify test/test/b
-----------
Since no files were changed between the runs, the second run should
never archive a file. But somehow verification corrupts the snapshot
file, and unchanged files are archived again.
The problem occurs on both of my i386 Etch systems (Etch with recent
security updates, kernel 2.6.21.3 from kernel.org, libc6 2.3.6.ds1-13)
as well as on a virtual i386 testing system running Etch with recent
security updates, Debian kernel 2.6.18.dfsg.1-12etch2, libc6
2.3.6.ds1-13).
Regards
Frank
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