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

[Gerhard Poul]

Robert Klima <address@hidden> writes:

> 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 updated (or from tars point of view outdated) by some other process.

I guess your problem is related to this documented behavior:

`--atime-preserve'
     Tells `tar' to preserve the access time field in a file's inode
     when reading it.  Due to limitations in the `utimes' system call,
     the modification time field is also preserved, which may cause
     problems if the file is simultaneously being modified by another
     program.  This option is incompatible with incremental backups,
     because preserving the access time involves updating the
     last-changed time.  Also, this option does not work on files that
     you do not own, unless you're root.

What I can't understand and reproduce is that you describe that the
problem doesn't appear to happen with device special files like
/dev/null. - I just tried it and it didn't work.

yours,
  gpoul