I'd look for a full disk first.

I'd boot from a live disk and then mount the partition(s) that Ubuntu
is on and check to see if they are full. Something like this:

ubuntu@ubuntu:/mnt$ sudo fdisk -l /dev/sda

Disk /dev/sda: 8589 MB, 8589934592 bytes
255 heads, 63 sectors/track, 1044 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sda1 * 1 993 7976241 83 Linux
/dev/sda2 994 1044 409657+ 5 Extended
/dev/sda5 994 1044 409626 82 Linux swap / Solaris
ubuntu@ubuntu:/mnt$ sudo mount /dev/sda1 /mnt
ubuntu@ubuntu:/mnt$ df -hl /mnt
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 7.5G 2.1G 5.1G 30% /mnt
ubuntu@ubuntu:/mnt$

In this example, only one partition is used, and it's at 30% usage. If
a disk gets to 100% or more (you can get a partition more than 100%
full, as there is space reserved for root), you might have trouble
logging in. I just happened to know that I had one SCSI disk in this
machine (a machine emulated in vmware), if you don't know, you'll have
to play around with "fdisk -l" (warning: fdisk without the '-l' can
destroy your system). A little intimidating to someone not used to the
command line, I'm afraid. IDE disks are /dev/hd(x), starting with x as
'a' and SATA disks are /dev/sd(x) named just like SCSI disks.

Of course, I'm sure there are numerous other problems that could cause
your problem in Ubuntu, but the first step in most troubleshooting
would be inserting an Ubuntu live disk...

>Device Boot Start End Blocks Id System
>/dev/sda1 * 1 993 7976241 83 Linux
>/dev/sda2 994 1044 409657+ 5 Extended
>/dev/sda5 994 1044 409626 82 Linux swap / Solaris

OK, got this done and found a list of my hard drives. Well,
really a list of my partitions -- they're all on one drive. SDA1 is
my XP partition and SDA2 is my Kubuntu partition.

>ubuntu@ubuntu:/mnt$ sudo mount /dev/sda1 /mnt
>ubuntu@ubuntu:/mnt$ df -hl /mnt

This one gave me an error that said something like "no such
directory" so I don't know what else to try.

>
>Of course, I'm sure there are numerous other problems that could cause
>your problem in Ubuntu, but the first step in most troubleshooting
>would be inserting an Ubuntu live disk...

Is there anything to be gained by simply re-installing
Kubuntu on top of what is already there?

Which of the two commands gave that error?

Given the layout of your disk, you'd want:

ubuntu@ubuntu:/mnt$ sudo mount /dev/sda2 /mnt

I was typing the /mnt$ -- I guess you'd expect that would
give me an error, but I'm pretty much ignorant of these things.

> Given the layout of your disk, you'd want:
>
> ubuntu@ubuntu:/mnt$ sudo mount /dev/sda2 /mnt

Nothing looks to be too full --

Filesystem 1K-blocks Used Available Use% Mounted on
tmpfs 354592 33788 320804 10%
/lib/modules/2.6.20-15-generic/volatile
tmpfs 354592 33788 320804 10%
/lib/modules/2.6.20-15-generic/volatile
varrun 354592 108 354484 1% /var/run
varlock 354592 0 354592 0% /var/lock
udev 354592 104 354488 1% /dev
devshm 354592 0 354592 0% /dev/shm
tmpfs 354592 12 354580 1% /tmp
/dev/sda2 11282776 2457244 8481664 23% /mnt

What else might keep me from logging in? I'm using the live CD to
post this, BTW...

I mounted sda6 and now both appear to be 100% full. Should I have not
mounted both at once?

I don't see /dev/sda6 You did not mention in your previous post what
sda6 was used for. You cab tell from your /etc/fstab file. When you
have /dev/sda1 mounted on /mount, that will be at /mnt/etc/fstab
assuming that /dev/sda1 is whyour system is, not sda6,

You can mount more than one partition on a single mount point at once.
You'll only see the last one you mounted. This is a bad practice for
this reason.

The last one -- ..............................

Yes, I apologize, I didn't give a full picture. I had
installed Dapper Drake on this machine and sda2 is where that
was. SDA6 is where Kubuntu 7.04 is installed, and it appears that
partition is 100% full. I still need to explore a little to figure
out some stuff. I had downloaded Xastir and tried to explode it, but
I'm really surprised the disk is full -- it should have a full 10
gigs available. Xastir should only be a few megs.

> You cab tell from your /etc/fstab file. When you
>have /dev/sda1 mounted on /mount, that will be at /mnt/etc/fstab
>assuming that /dev/sda1 is whyour system is, not sda6,
>
>You can mount more than one partition on a single mount point at once.
>You'll only see the last one you mounted. This is a bad practice for
>this reason.

That makes sense.

I'll try to show what it looks like here -- but the last one I copied
into an email didn't look so hot. Here's hoping this one is better.

ubuntu@ubuntu:~$ sudo fdisk -l /dev/sda

Disk /dev/sda: 80.0 GB, 80026361856 bytes
255 heads, 63 sectors/track, 9729 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Device Boot Start End Blocks Id System
/dev/sda1 * 1 7898 63440653+ 7 HPFS/NTFS
/dev/sda2 7899 9325 11462377+ 83 Linux
/dev/sda3 9326 9690 2931862+ 5 Extended
/dev/sda4 9691 9729 313267+ 88 Linux plaintext
/dev/sda5 9613 9690 626503+ 82 Linux swap / Solaris
/dev/sda6 * 9326 9591 2136582 83 Linux
/dev/sda7 9592 9612 168651 82 Linux swap / Solaris


> I still need to explore a little to figure
> out some stuff. I had downloaded Xastir and tried to explode it, but
> I'm really surprised the disk is full -- it should have a full 10
> gigs available. Xastir should only be a few megs.

How can I delete excess stuff to free up this disk? I'm looking at it
with the file browser, but I'm told I don't have the right permissions
to delete anything, and I'm not the owner so I can't change the
permissions.

> > You cab tell from your /etc/fstab file. When you
> >have /dev/sda1 mounted on /mount, that will be at /mnt/etc/fstab
> >assuming that /dev/sda1 is whyour system is, not sda6,

Changing to show sda6 instead of sda2, I see the following, but I
really don't know how to read it.

# /etc/fstab: static file system information.
#
#
proc /proc proc defaults 0 0
# /dev/sda6
UUID=8003e5a2-4287-41cc-93bd-a5e137f34d7e / ext3
defaults,errors=remount-ro 0 1
# /dev/sda7
UUID=47b999b4-4da8-4211-8004-67defa2c6d3f none swap sw
0 0
/dev/hdc /media/cdrom0 udf,iso9660 user,noauto 0 0

In a terminal window, type 'sudo nautilus' and enter your password when
prompted. This will run Nautilus with root permissions, allowing you to
delete *any* file - BE CAREFUL! The power this gives you means that you
can easily render your entire system unusable by deleting the wrong file.

Well I'm back in business, although I didn't really use this method.
I used the recovery mode and then deleted the Xastir folder I had
created. I sure didn't expect this partition to fill up so fast, I'll
have to see if it's as big as I wanted --

Hmm -- maybe I'm not recognizing the file structure. When I create a
directory, should I do it on my desktop? It appears the place where I
created it only has 346.4 mb, and 346.2 were already in use -- that's
/dev/disk

Conversely, my home directory shows to have nothing available at all.

Well it's fixed now! I used fdisk and deleted all
partitions except my XP partition and then reinstalled Kubuntu. Took
several tries, and what the heck does "Error 22" mean anyway? But
it's fixed now.

That is a GRUB error. See this post on Ubie forums how to fix it.
http://ubuntuforums.org/showthread.php?t=206262