Re: tar -c -G -N <date> query

[Tom Crane]

> Hello Tom!

Hi Stepan,
        Thanks the feedback.

> On Fri, Jul 04, 2003 at 10:36:37PM +0100, Tom Crane wrote:
[...cut...]
> > One other point: Are you sure the behaviour W.R.T. resaving unchanged 
> > files in a subdirectory which has had its mtime changed is different with 
> > '-g'.
> 
> No, I'm not sure.  All I can say is that it doesn't happen with the newest
> version of tar in my environment:
> > > I wasn't able to reproduce the bug, so I'd guess that it has been fixed
> > > in the last version (1.13.25).
> 
> So try to reproduce the bug with tar 1.13.25, and if the bug is still there,
> please write another bug report.  Take care to describe your environment,
> OS, OS version, gcc version, ...  (the tar source must contain some
> instructions about this somewhere).  Post the bug report to address@hidden
> and the tar maintainer (or someone else) should respond (I won't probably
> have time to work on it, sorry).

I've investigated with tar-1.13.25. I find that the bug (saving of
unchanged [neither ctime or mtime] files in a subdirectory, in an
incremental save, because the mtime of the subdirectory has been changed)
does still exist when using '-c -G -N <date>'. Using the '-c -g
snapshotfile', works properly -- ie. those files in the subdirectory are
not saved. 

One reason I was interested in using '-c -G -N <date>' was that a while
back I did a one-off, full backup of a machine, and spread it across
several CDs (ie. etcfull.tar.bz2, usrfull.tar.bz2, homefull.tar.bz2,
etc... on those CDs). I then wanted to do some 'proper' incrementals. The
problem was the original full saves were done without '-g' so I assumed
'-c -G -N <full backup date>' would be the way to go. The resultant
tarfiles are much larger than I wanted due to the unnecessary saves. My
problem with '-c -g snapshotfile', is that I don't have the snapshotfile. 

One question: Can I fabricate a snapshotfile? The format appear to be

time_t format timestamp
device_number directory-inode-number directory-spec
device_number directory-inode-number directory-spec
device_number directory-inode-number directory-spec
etc.

If I were to invent dummy device_numbers (or obtain the device-->numbers
mapping??), read the directory inode numbers and directory names out of my
*full.tar.bz2 tarfiles, and write them to a file with the above format,
would this do? 

Is there an better way of doing it?

Thanks
Tom.

Ps. System details -- Linux 2.4.19, egcs-2.91.66, glibc 2.1.3.
--
Tom Crane, Dept. Physics, Royal Holloway, University of London, Egham Hill,
Egham, Surrey, TW20 0EX, England. 
Email:  address@hidden
SPAN:   19.875
Fax:    +44 (0) 1784 472794