Lately I have been getting problems in Ubuntu 12.04, nautilus keeps crashing. The icons on my desktop disappear. Another click on files restores them.

Now I am sometimes getting stuck on boot, and I get what looks like kernel panic messages about 22 seconds into boot, then the computer freezes. Sometimes everything works.

Where will I find these messages, if the kernel managed to write them to the disc?

Also, I get something similar using Fedora 20 with KDE, I start Dolphin, it stops before I see any window, and the computer is frozen.

Up to now, this has not happened with gnome in Fed 20.

I ran memtest last night for 9 1/2 hours, 9 tests, 9 passes, no errors. This is a Toshiba Satellite C600D laptop.

Any tips on what the problem might be??

Logs like that are stored in /var/log/____

I'd look in:
Let us know how it goes!

Good luck!

Well I found this in /var/log/syslog.1

Mar 15 09:19:31 peterpu kernel: [11000.559358] gnome-settings-[1812]: segfault at 85e637f ip 085e637f sp bf9d0964 error 15
Mar 15 09:19:36 peterpu gnome-session[1760]: WARNING: Application 'gnome-settings-daemon.desktop' killed by signal
Mar 15 10:17:01 peterpu CRON[4530]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly)
Mar 15 11:17:01 peterpu CRON[4592]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly)
Mar 15 12:17:01 peterpu CRON[4660]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly)

What's a segfault? Sounds bad!

and this again, might be the crashes nautilus has been having.

Mar 15 09:19:31 peterpu kernel: [11000.559358] gnome-settings-[1812]: segfault at 85e637f ip 085e637f sp bf9d0964 error 15
Mar 15 09:19:36 peterpu gnome-session[1760]: WARNING: Application 'gnome-settings-daemon.desktop' killed by signal

and

Mar 16 13:10:56 peterpu kernel: [ 132.169438] show_signal_msg: 30 callbacks suppressed
Mar 16 13:10:56 peterpu kernel: [ 132.169453] nautilus[1855]: segfault at b747389b ip b6a04a44 sp bfa6ea9c error 7 in libc-2.15.so[b68c5000+1a4000]

and this from kern.log.1

Mar 12 17:19:55 peterpu kernel: [ 254.931957] indicator-print[1981]: segfault at 95b7080 ip 095b7080 sp bfe823c4 error 15
Mar 12 17:20:24 peterpu kernel: [ 284.122013] nautilus[1829]: segfault at 3924411c ip b6a09a0e sp bfd196ac error 4 in libc-2.15.so[b68ca000+1a4000]

Can you make any sense of that??

After several tries and booting an old kernel, I have got Ubuntu going again now on the newest kernel. I will look in the logs next time nautilus crashes.

Segfaults are bad.

It sounds like the gnome/nautilus code was trying to access memory out of range. That is bad. It could be that gnome and the kernel had a 'conversation' like this one:

Gnome: "I need _____ much memory to run."
Kernel: "Okay. I'll make sure you get that much."
Gnome: "Dude, where's my memory?"
Kernel: "It's there! I assigned it to you!"
Gnome: "Okay, but I can't access it."

Then SEGFAULT!!!

Haha okay so they didn't really have a conversation. But you get the idea. Gnome tried to access memory it couldn't, but expected to be able to, so it threw a segfault. It could be that using the updated kernel fixed whatever issue it was having. I hope so, anyway haha.

Anyway, good luck! I'm glad it's working for now. Hopefully it will continue to do so.

Hoped too soon! I just left home, closed down Ubuntu normally, come to the office, Ubuntu won't start. Good thing I keep Fedora 20 on another partition!

The apparent randomness of your issues makes me think three things to investigate: (1) Memory problems, (2) Power supply problems, and (3) Overheating problems.

You might try booting a LiveCD of Ubuntu 12.04 and running with that for a while to see if your problems still occur there. If so, I would tend to suspect a hardware issue even more.

How long would it normally take memtest to locate a problem? A while ago I ran it for 12 hours, no errors.

Also, about Fed 16 or 17, there was a problem: every time I unplugged the internet cable, the system froze. I just didn't use Fedora for a year or more. Now Fed 20 is fine. My logs show a segfault. This is happening since some recent update.

I do not rule out a hardware failure. But Fedora runs fine on the same computer, which points to other problems.

You may have TWO problems. This one:
And this one:
The first one sounds like possible hardware to me given it's randomness, the second one, like a software issue. But that's just a guess. It could be that a hardware problem is the root cause, and that hardware issue caused a software problem. Like this: Memory issue leads to -> corrupted data which is -> written to disk which leads to a newly created -> software issue. This resulting software issue may persist even if the initial hardware issue is subsequently fixed, or if the hardware issue dissappears temporarily (because it is intermittant).

I'm just guessing at all of this. These problems always seem baffling when you run into them. Then once you figure out what happened, all the pieces fall into place and everything seems so obvious. But it doesn't seem obvious at all when you're in the middle of trying to troubleshoot it!

Thanks for the comments

For the moment, I will solve the problem this way: use Fedora. In a couple of months I'll try Ubuntu again. If Fedora also starts crashing, then I'll buy another laptop! I saw a nice Samsung at a good price.

I also keep win on the first partition, for 2 reasons: I never found an OCR program with Linux which can compare with Abbyy Fine Reader, and my internet bank software only works with win. I rarely start win, but it has never crashed.

Well, I am running Fedora 20, using gnome 3.10 However, if I start Fed with KDE, it crashes when I try to run a program.

I am looking for a segfault in /var/log/ but there does not seem to be a syslog or a kernel.log in Fedora, but these are present in Ubuntu. Where should I look for possible problems??

Sorry for the late reply. I've been busy...

Anyway, according to the documentation for Fedora 20, found here [docs.fedoraproject.org], syslog was removed by default, and a different logging daemon was put in its place. I honestly have no idea how to use it, but about halfway down the page I linked there are some simple instructions.

I hope that helps...sorry I can't do much more. I'm not up on these newer init systems or logging capabilities. (I think they're both related, from what little I understood about what I've been reading about systemd, etc.)

Good luck!

Thanks, that helps. The problem hasn't reoccurred. If it does, I'll look in messages.