I'm not very impressed with Ubuntu 14.04 LTS so far

June 14, 2014

For various reasons I've only recently gotten around to doing anything with Ubuntu 14.04. Specifically I've been working on bringing up our new iSCSI backends on Ubuntu 14.04 instead of 12.04, since this obviously more desirable for machines that we expect to run for four or five years. As a result and to be blunt, I'm not particularly happy with Ubuntu 14.04 right now.

The most serious failure is that Ubuntu 14.04 has switched to the new style 'predictable' Ethernet device names without actually making them stable. On our iSCSI backend hardware the visible names of the 10G interfaces change from boot to boot (and some things suggest that even the management network interface name isn't stable). I fixed this with the blunt hammer of turning off predictable names entirely with 'biosdevname=0' on the kernel command line.

(Inspection of the usual entrails suggests that there is enough system information available that biosdevname should be able to come up with correct names in a stable way. As usual biosdevname does not come up with correct names. 'Predictable Ethernet device names' appears to be 'predictably wrong names' in practice.)

The next issue I ran into is a scary boot time stall with a message from Grub to the effect 'error: diskfilter writes are not supported'. It turns out that this has been an Ubuntu bug with mirrored system disks that's been known for months before 14.04 was released. The bug is harmless apart from giving you five seconds of fright as your system's boot stops, but its presence doesn't impress me with what people call the 'fit and finish' of Ubuntu 14.04.

We're also experiencing a weird SSH issue where with our configuration (which enables host based authentication and SSH (host) key signing), ssh to some hosts will spit out a message saying:

no matching hostkey found
ssh_keysign: no reply
key_sign failed

It does this in the middle of your regular ssh output, which can be kind of a problem. Again, this is at least a fit and finish issue.

(My co-workers are also not happy with 14.04 based on their own work with it, but I'm out of the loop there so I don't know any details.)

All of these leave me unimpressed with 14.04. What really irritates and worries me is that it seems unlikely that any of these will get fixed. Ubuntu has historically not really updated LTS releases apart from security fixes, and none of these three issues are likely to qualify under that policy. Since 14.04 was just released recently, maybe we'll get lucky and Ubuntu will fix these with official updates.

I also don't know if turning off biosdevname based Ethernet naming is officially or practically supported on 14.04. Lack of official support makes me worry that some future Ubuntu update will break things there, which of course would have very bad impacts the next time an iSCSI backend rebooted (or worse, if all of them did at once).

With the recent release of Red Hat Enterprise 7 and CentOS going full steam ahead on a prompt CentOS 7 release, it's now very likely that we'll jettison our previous plan of building our new iSCSI backends on Ubuntu and switch to CentOS 7 instead. At one level the distribution doesn't matter since we don't use any packaged software, but at another level we care a fair bit about whether the thing works and gives us a confident feeling about it. And Ubuntu 14.04 is failing at least the latter at the moment.

Written on 14 June 2014.
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Last modified: Sat Jun 14 01:48:23 2014
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