[Cialug] Filesystems!

[Todd Walton]

I learned today that a davfs mount can cause your computer not to boot
properly. I created the mount yesterday and it worked just fine. But
upon rebooting my computer I could not get past "emergency" mode.
(Single-user, essentially.) And I couldn't log into emergency mode
because root doesn't have a password! I appended "init=/bin/bash" to
the linux16 line in the grub entry and set a root password. Eventually
figured out that it was the mount. Rebooted and got to the graphical
screen.... and... it hung. I held down the shift key and whacked at
the numbers on the top row of my keyboard, but it didn't help. Then
figured out that if you change the root password that way you have to
also relabel the entire filesystem with security context
thing-a-muh-bobbers for SELinux. I'm all good now. Phew.

So I'm working on cloning a database server today, for another
emergency, and I discover a bit of weirdness. Tell me if I'm wrong,
but it seems a little silly to have multiple disks that are software
raided -- just raid 1, just a simple mirror -- and then LVM on top of
that raid array. And all of this on an AWS EC2 instance, so Amazon
*already* has the disks on some sort of high availability setup. I
understand using LVM for the flexibility of moving disks around,
growing, shrinking, whatever. But raid under that? In fact, I wouldn't
even use LVM's raid features. How likely is it that one of AWS's disks
is going to fail? And we're taking backups of the server.

So complicated.

--
Todd