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I've got a Slackware Linux cluster I'm planning on using for general-purpose shell accounts. Accounts are managed such that there are no UID or username conflicts among nodes. Given this, would NFS-mounting my utmp be a workable way of allowing, e.g., 'who' and friends to list everyone logged in anywhere in the cluster rather than just on the user's current node?

Obviously this would be contingent upon the node upon which utmp physically resides remaining available.

  • This wasn't intended to be shared, so I would expect subtle breakage... – Michael Hampton Dec 27 '13 at 0:04
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    The traditional answer would be to install rwhod and rwho on all your cluster nodes. Slackware packages these as netkit-rwhod and netkit-rwho, respectively. – Mike Renfro Dec 27 '13 at 2:33
  • The problem with that is that (as I understand it) they rely on broadcast messages on the local network. However, in my case the nodes aren't necessarily on the same local network, and when they are they aren't necessarily the only hosts on said local network. – Steely Dan Dec 27 '13 at 2:57
  • The first point could be a show-stopper. Most clusters aren't that spread out. You may be able to work around that with VLAN setup to make the physically separated hosts appear to be on one segment. For the latter, if the other hosts are trusted, it's not an issue. If they're untrusted, then you'd need to consider IPSec or Kerberos for securing NFS. Regardless, sharing utmp probably won't work. Maybe run a cron job on each system with the output of who, and make the output web-accessible? – Mike Renfro Dec 27 '13 at 13:02
  • A similar solution had crossed my mind, except instead of web-accessible it'd involve rewriting who to draw on a similar source. The utmp-sharing option seemed much simpler if it would actually work, though, so I figured it was worth investigating its feasibility first. – Steely Dan Dec 28 '13 at 5:48

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