Ubuntu hangs after few hours of nonstop operation

I don't know, but you can use the `free` command to check what your current memory usage is.

Do you have swap space?

Have you run a memory test? A memory issue is a possibility with what you're describing.

memory module is brand new, i don't think the problem is with the memory module. 'free' did throw some light on the issue. my swap space was showing '0' under total, though i had a swap space of 1.94 GiB, turns out swap was disabled somehow. i have enabled it for now but whether that solves the problem is yet to be seen. i will reply after my tests. thanks guy's.

memory module is brand new, i don't think the problem is with the memory module. 'free' did throw some light on the issue. my swap space was showing '0' under total, though i had a swap space of 1.94 GiB, turns out swap was disabled somehow. i have enabled it for now but whether that solves the problem is yet to be seen. i will reply after my tests. thanks guy's.

ignore the third post, pressed 'problem solved accidentally'.

ok, looks like it is a swap space problem. every time i boot, i find that my swap space is switched to off. how to fix this guy's.

Have a look at your /etc/fstab file, is there a line like;

/dev/sda<n> none swap sw 0 0

in it?

If not, you can add it manually using "sudo swapon -a". From the swapon manual page:

       -a, --all
              All devices marked as ``swap'' in /etc/fstab are made available, except for those with the ``noauto'' option. Devices that are already being used
              as swap are silently skipped.

Correction, I meant add it manually then activate it with "swapon -a"

# /etc/fstab: static file system information.
#
# <file system> <mount point> <type> <options> <dump> <pass>
proc /proc proc defaults 0 0
# /dev/sda1
UUID=f91bb02e-ad1c-4ca8-a4cd-9e7aa6d25d91 / ext3 relatime,errors=remount-ro 0 1
# /dev/sda3
UUID=6452abe2-4c9f-4635-8ca8-cd7ddbdd30cf none swap sw 0 0
/dev/scd0 /media/cdrom0 udf,iso9660 user,noauto,exec,utf8 0 0
usbfs /proc/bus/usb usbfs devgid=14,devmode=0660 0 0

this is my fstab, i see that the entry is there but not quite the way you said it would be, There is a # before the /dev/sda3 and the swap space is mentioned by the UUID.

swapon -a produces this at the terminal

root@nakedpc:/etc# swapon -a
swapon: cannot stat /dev/disk/by-uuid/6452abe2-4c9f-4635-8ca8-cd7ddbdd30cf: No such file or directory
root@nakedpc:/etc#

Please copy and paste here the result of this terminal command:

cat /etc/fstab

Thank you

Sorry wait ok there is already here...

Thanks marcobra (Marco Braida), that solved my question.

for anybody facing the similar problem, go to the link suggested by marcobra and follow post #23. it works.