Ubuntu :: Sda1 Full, Cleanup Commands Not Working

I have had the same problem of /dev/sda1 becoming full and have been able to fix it with the commands:

sudo apt-get clean
sudo apt-get autoremove
sudo dpkg --configure -a
sudo apt-get update
sudo apt-get upgrade

But this time I am still unable to free significant space. Here is the output of various commands.

df -h
/dev/sda1 5.6G 5.4G 0 100% /
varrun 498M 108K 498M 1% /var/run
varlock 498M 0 498M 0% /var/lock
udev 498M 76K 498M 1% /dev

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