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The problem When I boot Ubuntu 11.10, the boot process hangs, before even getting to the login screen of the display manager, with the message

Could not write bytes: broken pipes

at the top of the screen, followed by some lines of text (where one yellow star left of "PulseAudio" is - don't know if this is important...), the last being

* Stopping System V runlevel compatability                                          [Ok] 

After that I can only press Ctrl+Alt+Del to reboot.

The cause The problem occured after I did an update on feb., the 18th. In the process of the update a window popped up in which I had to choose the default display manager. Being in a hurry, I just clicked "ok" (gdm was the default selection in that window). Afterwards I found out that Ubuntu 11.10 us es lightdm so I figured, that maybe this was the cause of my problem. Before this update everything worked fine.

{What I tried so far to do to fix it [skip this, if its too long] I logged in as root in recovery mode and tried to reinstall lightdm. Using the apt-get command I get error that spans over 3 lines of text, the first of which is

Not using locking for read only lock file /var/lib/dpkg/lock;

but I don't know of any process that is using apt-get, that is preventing it from being run.

After that I used dpkg-reconfigure lightdm and selected lightdm as the default display manager. This exited with the line

mv: cannot move 'etc/X11/default-display-manager' to '/etc/X11/default-display-manager.pdkg-tmp': Read-only file system".

When I then booted in normal mode it still hung, but the message Could not write bytes: broken pipes was gone, there were just two lines of text, the first said something about the battery state and the last was identical to the one above ("* Stopping System V[...]"). I played around a little bit by also trying dpkg-reconfigure gdm and choosing gdm instead of lightdm, but none of that helped. The system still hangs, just with different lines of text showing up, but "* Stopping System V[...]" is always the last one. }

Other info This may be or not be relevant: I use multiple operating systems (the other ones work) and the kernel I use is 3.0.0-15-generic-pae.

Please help, I invested so much time in setting my Ubuntu system up, I don't want to do it all over again.

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1 Answer 1

up vote 10 down vote accepted

Actually, what's going on is when you go into recovery your disks are mounted as read-only. I just did this and for some reason the Mount Disk option didn't work, so I just hit the 'root' option and used:

mount -o remount,rw,errors=remount-ro /

This makes your drive writable. Once you do that you should be able to do your dkpkg-reconfigure lightdm

If it still says "read-only filesystem" then do the opposite and start a disk check:

mount -o remount,ro /
rootpartition=$(cat /etc/fstab | grep -E "# / was on .*installation" | awk '{print $5}')
e2fsck $rootpartition

If you can't remember that big long rootpartition= string, you can also get the device by going to /dev/disk/by-uuid use the file that is a big 36-character string (it should be the only one if you don't have any other Ext partitions). So, it would look something like this (using my UUID): fsck /dev/disk/by-uuid/062b52ee-5df4-4ad2-829e-0734f822748c

If any errors are found, be sure to restart!

In fact, I had this exact same problem when trying to nuke Unity and uninstalling unity-greeter (even though lightdm was still installed). I think it removed /etc/lightdm/unity-greeter.conf but left /etc/lightdm/lightdm.conf (which has a reference to unity-greeter.conf) unchanged. That makes sense why it wouldn't boot, though I didn't think to look and just re-installed unity-greeter once I worked my way past the read-only issue I was having.

Anyway, give it a shot!

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Hey, thanks a million times, doing in root first mount -o remount,rw,errors=remount-ro / and then dkpk-reconfigure lightdm worked! (Wish I could upvote, but I have to few reps) Do you have any idea though, why it now takes well over 30 seconds until ubuntu gets from the login to desktop, whereas earlier it took at most 7 ? –  user10324 Feb 20 '12 at 14:27
1  
Probably because ureadahead was re-profiling. Anytime you modify a package involved in the start-up ureadahead (the boot caching program) has to re-make its database. Subsequent restarts should be well improved. –  Githlar Feb 20 '12 at 15:16

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