On Ubuntu Tweak, it says that Janitor can be run to free up some disk space. Is this safe? I am running 12.04.
I know you already got your answer, but I somewhat recently went through ubuntu-tweak's source (when it was announced that it wasn't going to be developed any longer) and translated everything that it did to the equivalent in bash. If you're interested to know, Ubuntu Tweak does nearly exactly:
sudo rm -rf /var/cache/apt/archives/*.deb
sudo apt-get clean
rm -rf ~/.cache/google-chrome/Default/*
rm -rf ~/.cache/chromium/Default/*
rm -rf ~/.cache/telepathy/Cache*
rm -rf ~/.googleearth/*
rm -rf ~/.cache/gwibber/
while read -r line; do if [[ "$line" == Path=* ]]; then rm -rf ~/.mozilla/firefox/${line:5}/Cache/*; rm -rf ~/.mozilla/firefox/${line:5}/OfflineCache/*; fi; done < ~/.mozilla/firefox/profiles.ini
while read -r line; do if [[ "$line" == Path=* ]]; then rm -rf ~/.thunderbird/${line:5}/Cache/*; rm -rf ~/.thunderbird/${line:5}/OfflineCache/*; fi; done < ~/.thunderbird/profiles.ini
rm -rf ~/.opera/cache/*
dpkg --list |grep "^rc" | cut -d " " -f 3 | xargs sudo dpkg --purge //this one may be dangerous. only run if you know what it's doing.
rm -rf ~/.cache/software-center/*
rm -rf ~/.thumbnails/*
dpkg -l 'linux-*' | sed '/^ii/!d;/'"$(uname -r | sed "s/(.*)-([^0-9]+)/1/")"'/d;s/^[^ ]* [^ ]* ([^ ]*).*/1/;/[0-9]/!d' | xargs sudo apt-get -y purge
And here's a link to my original comment on the matter from reddit.
