Power Outage and Improper Shutdown

[audiomick]

There is no "man" for /forcefsck because, I think, that is a file.
According

man touch

touch is a command to change the timestamp on something, so I think

sudo touch /forcefsck

doesn't directly call up "fsck" itself, but rather, it "tricks" the mechanism that invokes the regularly scheduled file check into thinking it is due on the next boot.

I think if you want to run "fsck" with specific options, the easiest would be to run it from a live CD.

"non-contiguous" is the state that is corrected by a de-fragmentation. It means that bits of a file are stored at different locations, instead of the file all being in one block. I don't think that this is a problem, particularly at that low percentage, but maybe someone else knows something to the contrary.

[LRT]

so I think

sudo touch /forcefsck

doesn't directly call up "fsck" itself, but rather, it "tricks" the mechanism that invokes the regularly scheduled file check into thinking it is due on the next boot.

this makes sense, thanks.

I think if you want to run "fsck" with specific options, the easiest would be to run it from a live CD.

I'm going to try this, but it would be nice to know if there is a way of doing this (filesystem check with automatic repairs at boot time) without the live CD. This is what I really want to be able to do.

"non-contiguous" is the state that is corrected by a de-fragmentation. It means that bits of a file are stored at different locations, instead of the file all being in one block. I don't think that this is a problem, particularly at that low percentage, but maybe someone else knows something to the contrary.

Well, before the power outage, I've never seen this "non-contiguous" message during one of the regularly scheduled disk checks that happen every 20 boots or so... So was this fragmentation caused by the power outage? I don't know.

[bodhi.zazen]

There is always some degree of fragmentation, a few % is nothing to be concerned with.

Fragmentation is only a problem when it becomes severe enough to affect performance, and is rare with Linux.

ext4 and btrfs have the capability, in theory, for defragementation, but I have not seen it implemented as of yet.

http://geekblog.oneandoneis2.org/ind..._defragmenting

By comparison, I have seen scans on Windows boses running slowly where fragmentation is in striking, 50 %, 200 % , and up.

Here you can see , Windows seems to feel 7 % fragmentaion is "OK"

http://blogs.technet.com/askperf/arc...rformance.aspx

[audiomick]

...if there is a way of doing this (filesystem check with automatic repairs at boot time) ...

I really don't know for sure, but I have a feeling that this is what it does. Don't know where to look to find out, sorry.

Well, before the power outage, I've never seen this "non-contiguous" message during one of the regularly scheduled disk checks that happen every 20 boots or so... So was this fragmentation caused by the power outage? I don't know.

I doubt that the "out" caused it. Fragmentation happens when the file system is running correctly and decides it needs to break up the file. Imagine putting your shoes in an overfull cupboard. If you are able to complete the job, you might end up with one on the top shelf and the other on the bottom shelf. If the door bell rings in the middle of things, you might end up with one in the shelf, and the other on the floor, i.e. a broken file.

as bodhi.zazen pointed out, windows systems create some astonishing amounts of fragmentation and live with it fine, if slowly. A couple of percent is not an issue.

[LRT]

well i ran fsck from an ubuntu live cd. the check was very quick, practically instant.

fsck -aCVt ext3 /dev/sda3

output told me the filesystem was clean, so i guess all is good. thanks for the help!

like i said, would be nice if i can do this without the live cd, and on the next boot instead.

[tgalati4]

Well if you look at the bootup messages (Alt-F1) if you don't see them during boot, you will see that an fsck is automatically performed on all filesystems that are mounted. So a hard power off will automatically trigger an fsck on the next power-on.

If fsck encounters errors that can't be fixed automatically, then you are dropped to a limited shell where you can run fsck manually and interactively and try to recover the disk. Normally, a severe head crash will lose some files and the fragments will appear in /lost+found.

That is why an UPS is important. You want to keep those disks spinning and the server humming along.