Re: New!!!: Base-passwd 2.0
> Philippe Troin:
> > Is there a debian standard way of [ locking /etc/passwd and friends ] ?
>
> I don't think so, at the moment. It should be doable, however. We
> have a locking policy for mailboxes. I'm sure we can have one for
> /etc/passwd.
Oops. I should pipe up. There is already an established locking method
for /etc/passwd and /etc/group (implemented in NIS and in passwd/group
related utilities at least in SunOS).
I used to code directory admin tools for the Northern Telecom IT group.
During my time there I confirmed that at least passwd(1), rpc.yppasswd
and vipw (which doesn't seem to be in Debian) in SunOS conformed to the
following mechanism.
If memory serves the mechanism is:
1) open(2) /etc/ptmp (with O_CREAT|O_EXCL)
(if that fails, wait and try again)
2) read in /etc/passwd and write changed passwd file to /etc/ptmp
(in this way /etc/passwd is maintained intact for others to use
while you make your changes)
3) rename(2) /etc/ptmp to /etc/passwd
(rename is a guaranteed atomic action)
The same is tru for /etc/group except that /etc/gtmp is used.
NOTE: this is strictly from memory, I'd have to look at the source for
passwd(1), rpc.yppasswd and others to confirm this. And unfortunately
I'm late for a meeting right now. I'll try to look and get back to the
list this evening.
I hope this helps.
Behan
--
Behan Webster mailto:behanw@verisim.com
(613) 224-7547 http://www.verisim.com/
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