[Mailman-Users] permission for archives

Stephen J. Turnbull stephen at xemacs.org
Wed Jun 17 09:37:32 CEST 2015

Mark Sapiro writes:

 > The safe thing is for 'you' to not have write permission on the mbox. If
 > you did have in the past, this may be how the group was changed.

Quite likely.

Basically, there are two ways to change the content of a file on
Unix-like systems.  One way is to write-lock (at least) the file, and
open it read-write.  Then do your edits, and close the file.  Voila!
the new contents are there, and the properties of the file (which are
stored in the directory entry, not in the file) do not change.

The second doesn't require locking the file (although in the mail
context you probably want to, since the MTA can add new messages while
you are working with the file in your MUA, and in the simplest version
of this strategy those new messages would be lost).  You make a copy
of the file under a temporary name, edit the copy, and then rename the
file to the old name (usually also renaming the old file for backup).
Under Unix semantics, the new file's directory entry gets *your* owner/
group/umask settings, and renaming just changes the name.

It turns out that on modern Unix systems ordinary users are not
allowed to give arbitrary owner and group properties to a file, so if
your editor or MUA uses the copy-edit-mv strategy, the file's
ownership *will* change.  Probably alpine uses this strategy.

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