I had to reboot a server this morning that had been up for 430+ days. On reboot it started a forced filesystem check. The problem is that one of the filesystems is a 300gig LUN from the SAN. Is there anyway to cancel out of the filesystem check once it's started without risking any data loss?

Why was it up for 430 days? Never updated the kernel, eh? Security not a concern of yours? Might want to reconsider that, but as to your question:

As to cancelling it once started, I wouldn't do that. Not sure how, either.

But you can change how often it happens: man tune2fs

thanks. I ended up just ctrl-c'ing out of it.

I would love to be able to have routine updates to all my servers, but certain customers demand virtually 100% uptime. So long as the box is stable, they will not approve a reboot or upgrade. :/

Also, there are VERY few remotely-exploitable kernel vulns, so you usually just patch software and still be safe. Upgrading a kernel on a production system without a particular reason is a bad idea.

That being said -- fsck can be useful to avoid more severe corruption down the road. 300G is really not that bad for fsck on a modern system, particularly on journaled filesystems where it can skip some of the normal steps.

I've seen systems up for longer periods of time. Not everyone needs to update their kernel on a daily basis or every release, that would be a sysadmin's nightmare if that were a requirement. If it's not an exploitable kernel vulnerablity and they don't need to recompile for hardware changes as that might change once every 5 years in some production environments, there's really no need to update the kernel. This could be a setup behind on a private network for all we know. I still run 2.4.32 on my own servers, with no need to update still even. But from my experience as a system administrator, only upgrade if it will directly impact you, other than that, a production system should never be updated on a daily type basis or when a new release is out without testing first. Also in my experience, usually the latest and greatest has more unknown vulnerabilities than the older proven stable releases where they've worked out all the known bugs, etc.