Oracle 11g R2 installation on Ubuntu 14.04 LTS I have installed Oracle 11g R2 on ubuntu 14.04 LTS.
On terminal I wrote following to start oracle:

sudo service oracle-xe start


on pressing enter, got following output :

" Starting Oracle Net Listener.
  touch: cannot touch '/var/lock/subsys/listener' : No such file or directory
  Starting Oracle Database 11g Express Edition instance.
  Failed to start Oracle Net Listener using /u01/app/oracle/product/11.2.0/xe/bin/tnslsnr
  and Oracle Express Database using /u01/app/oracle/product/11.2.0/xe/bin/sqlplus. "


What should I do now.
try these commands on terminal :

sudo mkdir -p /var/lock/subsys

sudo chmod -R 777 /var/lock/subsys