Hello,
When I extract a tar archive over existing contents, I’m seeing:
/usr/bin/gtar: mail/dovecot-uidvalidity.5e8a8de1: Cannot open: Permission denied
The file in question has 0444 permissions but is owned by the same user
as the one running tar. I guess tar doesn’t chmod() the file in order to
overwrite it?
Anyway, I then tried adding “--unlink-first”, but that produced a bunch
of warnings about unlink()ing nonempty directories. (bug?)
I next tried “--recursive-unlink”, and this seems to fix my problem,
though I wonder about the disk I/O hit if it’s a large hierarchy being
overwritten.
What if tar were instead to overwrite files instead by writing to a
temporary file in the same directory, then rename()ing the newly-written file
into place? Then directory hierarchies could stay as they are during
extraction, and the 0444-perms-as-user problem would be avoided as well. (It
would assume, of course, that the user has write permission on the directories.)
Thank you for your time!
-Felipe Gasper
