This command can be used to start mysql service when it is stopped due to drive full

From command line issue the below command

tune2fs -m 0 /dev/sda5

This can save a little space enough to start mysql.

Now find out the reason to become the drive full. The below command can be used to list biggest 10 files:

du -a / | sort -n -r | head -n 10

If it is because any log file, delete it. If it is because of ibdata, the mysql file, follow the below steps to shrink it.
Also, check the possibility of reducing size by deleting old data from tables like STOCKDIARY, TAXLINES, etc.,

To shrink ibdata file, follow the below steps:
1. Connect a usb drive and mount it.
2. From command line issue below commands

mysqldump -u root -p SALECULATOR > /flash/fullbak.sql  (enter password)
mysql -u root -p (enter password)
DROP DATABASE SALECULATOR;
exit;
service mysql stop
rm /data/db/ibdata1
rm /data/db/ib_log*
service mysql start
mysql -u root -p (enter password)
CREATE DATABASE SALECULATOR;
USE SALECULATOR;
source /flash/fullbak.sql;
exit;
exit