1. howto check file's size

du -m/-sh filename

2. to make root_fs

mkyaffsimage root root.yaffs

3. to remove installed package with configration files( a complete removal of package )

apt-get --purge remove packagename

4. to get many details about the package that you want (or don't want)to install

apt-cache show package

The output include the information of the package which has been installed in your system

5. to check file's type

file filename