[Bug-tar] Using --verify and --one-file-system causes verification failures / false difference

[John Thomas McDole]

Hi,

I'm using gnu tar 1.15.1 in a backup script and I believe I've found a 
bug.  The following command line shows the options I've selected:

# /bin/tar --verify --totals --create --preserve-permissions 
--absolute-names --one-file-system --label full.jmcdole2.2005-10-20 
--file full.jmcdole2.2005-10-20.tar --verbose --listed-incremental 
full.jmcdole2.2005-10-20.snap /home/jmcdole/ >> 
full.jmcdole2.2005-10-20.log 2>&1

Tar fails with an exit status of 1. The log shows that several 
directories failed verification ("/home/jmcdole: Contents differ", ...). 
 A quick diff/compare with the following:

# tar -df full.jmcdole2.2005-10-20.tar

compares successfully, showing no errors (exit status 0).  Using the 
same command again, appending one-file-system:

# tar -df full.jmcdole2.2005-10-20.tar --one-file-system

returns the same directories reported as differing in the log file (exit 
value of 1).


If I issue:
# /bin/tar --verify --totals --create --preserve-permissions 
--absolute-names --label full.jmcdole2.2005-10-20 --file 
full.jmcdole2.2005-10-20.tar --verbose --listed-incremental 
full.jmcdole2.2005-10-20.snap /home/jmcdole/ >> 
full.jmcdole2.2005-10-20.log 2>&1

then I get no verification errors.


Even more curious is that the snap (incremental files) differ only by 
the first line:
1c1
< 1129818118
---
> 1129818565

and a hex dump of both files, followed by a diff shows only header 
information:
# colordiff full.jmcdole.2005-10-20.hex full.jmcdole2.2005-10-20.hex
1,2c1,2
< 00000000  66 75 6c 6c 2e 6a 6d 63  64 6f 6c 65 2e 32 30 30 
|full.jmcdole.200|
< 00000010  35 2d 31 30 2d 32 30 00  00 00 00 00 00 00 00 00 
|5-10-20.........|
---
> 00000000  66 75 6c 6c 2e 6a 6d 63  64 6f 6c 65 32 2e 32 30 
|full.jmcdole2.20|
> 00000010  30 35 2d 31 30 2d 32 30  00 00 00 00 00 00 00 00 
|05-10-20........|
6c6
< 00000090  35 35 30 00 30 30 35 31  33 31 00 20 56 00 00 00 
|550.005131. V...|
---
> 00000090  33 30 32 00 30 30 35 32  30 36 00 20 56 00 00 00 
|302.005206. V...|


Since there are no extra file systems underneath (no links to other file 
systems; all files are regular or directories), one would thing the 
--one-file-system option wouldn't cause a problem.  Since I do have 
other backup directories that have other file systems that don't need to 
be backed up, the work around is to include the other file systems in an 
exclude file:

# cat public.exclude
/export/public/tmp

and include it with the "--exclude-from=", removing the 
"--one-file-system" from the equation.

--
John Thomas McDole
<address@hidden>
Nagra STB Technologies Software Engineer
938 Peachtree St. NE
Atlanta, GA 30309-3919  [USA]
+1.404.525.0940 x126 [voice]