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Re: [Xen-devel] [PATCH] libxl: prevent xl from running if xend is running.

Ian Campbell escribiÃ:
On Tue, 2012-04-24 at 15:47 +0100, Ian Jackson wrote:
Ian Campbell writes ("Re: [Xen-devel] [PATCH] libxl: prevent xl from running if xend 
      is running."):
You could consider this to be a best effort check for xend. IOW we try
and look but if we can't tell then we assume it is not.
I guess.

It's not terribly robust to just blunder on, but on the other hand being
more robust has a bigger risk of false positives, e.g. failing to start
xl because /var/lock/subsys/ does not exist isn't especially helpful
either (the EACCESS return code doesn't distinguish that
from /var/lock/subsys/xend not existing).
EACCES would happen only if the permissions prevented us from
looking.  If /var/lock/subsys doesn't exist we'll get ENOENT, the
"good" error return.

Oh, right.

Well, not starting because the perms on /var/lock/subsys are too tight
(e.g. selinux restricting it to initscripts only? unrealistic maybe)
seems unhelpful too.

(I admit this isn't as compelling as my previous example).


What have we decided at the end? Should I do an inverse check, and run only if access(...) != 0 && errno == ENOENT?

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