Ubuntu Package Installation

Install
  sudo apt-get install openssh-server
Remove
 sudo apt-get remove openssh-server
apt-get --purge remove

Show installed packages

dpkg --get-selections | grep php

Install 

$ sudo dpkg -i package.deb

Remove
$ sudo dpkg -r package

To check installed package

$ sudo dpkg -s package 

List all installed pkg

$ dpkg --get-selections

$ dpkg --get-selections | grep required  

Enabling Core on Ubuntu

Check  
 ulimit -c   It should not be zero.
set ulimit -c unlimited

1. Vim /etc/sysctl.conf
2. Add the lines:
   kernel.core_uses_pid = 1
   kernel.core_pattern = core-%e-%s-%u-%g-%p-%t    
   fs.suid_dumpable = 2
3. If  we need to redirect core in some path mention that in kernel.core_pattern = /tmp/core-%e-%s-%u-%g-%p-%t
4. sysctl -p