not enough disk space when updating

d950@d950-Ubuntu:~$ sudo apt-get clean
[sudo] password for d950:
d950@d950-Ubuntu:~$ sudo apt-get clean
d950@d950-Ubuntu:~$ sudo apt-get clean
d950@d950-Ubuntu:~$ sudo df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda5 2.3G 2.2G 49M 98% /
tmpfs 994M 0 994M 0% /lib/init/rw
varrun 994M 104K 994M 1% /var/run
varlock 994M 0 994M 0% /var/lock
udev 994M 148K 994M 1% /dev
tmpfs 994M 528K 993M 1% /dev/shm
lrm 994M 2.7M 991M 1% /lib/modules/2.6.28-11-generic/volatile
d950@d950-Ubuntu:~$

It appears to me that not enough diskspace is allocated by the installer. I am able to install some of the updates but it finaly chokes. I see that only 2.3 GB is allocated and some of the update messages
say I need another 400 plus MB. Disk space is cheap these days so why not allocate 20 GB if available. This unit I am testing on has 149 GB available which should be plenty of room for Windows 7 and Ubunto. I'm not a Unix person so I may be off track.
Does Unix have the ability to change the disk space after the fact?
Paul

ProblemType: Bug
Architecture: amd64
DistroRelease: Ubuntu 9.04
ExecutablePath: /usr/bin/gnome-terminal
Package: gnome-terminal 2.26.0-0ubuntu2
ProcEnviron:
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: gnome-terminal
Uname: Linux 2.6.28-11-generic x86_64