So I tried using 'parted' to resize a partition. What a huge mistake that was. Don't ever use 'parted' unless you enjoy being tortured for your unfamiliarity.
- It doesn't clarify ambiguities in units of measurement.
- It completely ignores your response to "Yes/No?" questions and executes the command anyway, leaving a result that's orders of magnitude different than you intended
- Changes are immediate - it doesn't buffer the changes and give you the opportunity to quit without applying them
So basically if you make a mistake, it will let you know just to tease you and then apply the changes anyway.
I accidentally shrunk the thing twice, both times saying "n" and "No" to the ensuing prompt, before getting it correct. Whatever it did, after making a seemingly correct and working resized partition in gdisk, apparently there was some damage hidden underneath. It wasn't obvious until I rebooted.
Upon rebooting the server couldn't mount that partition anymore. e2fsck now says an ext4 "superblock" got corrupted and I have no clue about that kind of thing.
I'm now cloning the whole fubared drive to an image file in the blank space on a new hard drive, which fortunately is just barely big enough to hold it. That will take 12 hours.
After that I'll reformat the fubared drive, cross my fingers and hope that SnapRAID can recover it's contents. I expect that to take just as long.
If that fails, I'll be trying to figure out how to mount the corrupted image file and get my files back out of it.
I should have taken the time to hook up a CDROM drive and used gParted. That frontend is what makes the whole thing usable. I thought 'parted' would be the same thing in text, equal in user friendliness to 'fdisk' and 'gdisk', but hoo boy was I wrong.