[SOLVED] clear unnecessary systemfiles eating up my drive space

[antonio_helder2002]

I dont have a HDD so i run ubuntu from a 2GB pen drive. in that 2 GB pen drive i have made 2 partitions of 1.04 GB & 850MB. The 1.04 GB is used by me as my booting space while i store files in my 850MB.
now i have installed video & audio codecs in it also. i have also included in it CHM viewer
the problem that is standing for me is when ubuntu boots up it is eating up 2 MB of space each time due to which after 20 or 30 boots the boot process becomes very slow & i have to reinstall the OS & everything all over again. now i have to clear this space taken up by unnecessary file.
how do i do it??
only terminal commands are invited.

[devils casper]

Execute this to clean cache :

sudo apt-get clean all

Execute this to remove log messages :

cd /var/log
sudo rm -f messages.*

[antonio_helder2002]

Execute this to clean cache :

sudo apt-get clean all

Execute this to remove log messages :

cd /var/log
sudo rm -f messages.*

Problem solved