in order to clean automatically .sock file, place these lines in file /etc/init.d/mysqld immediately after "start)" block of code
test -e /var/lib/mysql/mysql.sock
SOCKEXIST=$?
ps cax | grep mysqld_safe
NOPIDMYSQL=$?
echo NOPIDMYSQL $NOPIDMYSQL
echo SOCKEXIST $SOCKEXIST
if [ $NOPIDMYSQL -eq 1 ] && [ $SOCKEXIST -eq 0 ] ; then
echo "NOT CLEAN"
rm -f /var/lib/mysql/mysql.sock
echo "FILE SOCK REMOVED"
else
echo "CLEAN"
fi
it worked for me. I had to do this because I have not an UPS and often we have power supply failures.
regards.