tar 1.23.xx when using --preserve-atime and --listed-incremental

[Robert Klima]

Big sorry if you recieve this e-mail twice.

After not having recieved any feedback I wondered wether the mailbox
is still being read and found at least the adress to be outdated. :-)

----- Forwarded message from robert -----

To: address@hidden
Cc: address@hidden
Subject: tar 1.23.xx when using --preserve-atime and --listed-incremental

Dear Madam dear Sir,

please allow me to report some obscure behaviour of tar using 1.13.17
through 1.13.25 on variuos linux-2.4.x-i386 systems e.g. Debian 3.0.

When --preserve-atime is used in connection with --listed-incremental
a snapshot is created but not taken into account for reduction of the
created archive (in relation to a full dump). See the shellscript below
for an example. Whats even more confusing is that it works as supposed
when using /dev/null as a target. Pay attention to the lower two examples
which hint at some system resource being reused after having become
updated (or from tars point of view outdated) by some other process.

If there wasn't the latter behaviour I would have recommended not taking
ctime into account in incremen.c when using --preserve-atime. Otherwise
one could make both options mutually exclusive. Could also imagine that
reference to some stat-struct produced by the kernel was handed through
instead of making a copy.

Please tell me wether you found this bug report useful. :)

Yours sincerly, Robert Klima.

#!/bin/bash

B="backupthis$$"
S="snapshot$$"
mkdir $B
for R in 1 2 3; do
  echo $R >$B/$R
  sleep 1
  #Example of misbehaviour
  tar cvf result$R.tar $B -g $S --atime-preserve
  #BAD : tar cvf result$R.tar $B -g $S --atime-preserve
  #GOOD: tar cvf /dev/null $B -g $S --atime-preserve
  #GOOD: tar cv $B -g $S --atime-preserve >/dev/null
  #BAD : tar cv $B -g $S --atime-preserve >result_stdout.tar
  sleep 1
done
rm -r $B
rm result*.tar $S

----- End forwarded message -----

-- 

Gruss, Robert.
-- 
Robert Klima - http://www.tvk.rwth-aachen.de/~robert/info.html

Fertility is hereditary.  If your parents din't have any children,
neither will you.

Gruss, Robert.
-- 
Robert Klima - http://www.tvk.rwth-aachen.de/~robert/info.html

Linux is like a wigwam: no Windows, no Gates, Apache inside