Just download the LXSPLIT software from ( http://www.freebyte.com/download/lxsplit.tar.gz
untar it using the command
$ tar -xvzf lxsplit.tar.gz
$ cd lxsplit-0.1.1/
Here just follow the instruction given in the README file. It's very easy to install.
After installing you can split the files using the command line
$ lxsplit -s filename size
for example if you want to split a 700 mb file named "something.avi" into 7 pieces each of 100 mb then just type
$ lxsplit -s something.avi 100m
Here "-s" stand for splitting
"100m" stands for size of the splitted file.
after this you can see the splitted file in the same directory named
For joining the splitted file just type
$ lxsplit -j filename.001
Here "-j" stands for joining and remember you have to type the name of the first splitted file i.e. " filename.001".It automatically searches for the rest of the file in the same directory.