SSH config: command for bastion server proxying

Host 51.21.21.11
  IdentityFile ~/.ssh/mykey.pem
  User ec2-user
  ForwardAgent yes

Host 10.*
  ProxyCommand ssh ec2-user@51.21.21.11 nc %h 22
  User ec2-user
  IdentityFile ~/.ssh/mykey.pem
  ForwardAgent yes

Put your ssh public key in ~/.ssh/authorized_keys along the path.

telnet vs netcat

1. netcat
1. prints only what is sent by the remote host
2. telnet
1. not suitable for arbitrary binary data 
1. reserves some bytes as control characters 
2. quits when its input runs out
1. you may not see what the other end sends
3. doesn't do UDP

Ubuntu: convert desktop to server fast

Below as root:

1. apt-get remove ubuntu-desktop
2. apt-get install linux-server linux-image-server
3. apt-get purge lightdm
4. /etc/default/grub, change matching lines to below
1. #GRUB_HIDDEN_TIMEOUT [comment it out]
2. GRUB_CMDLINE_LINUX_DEFAULT=""
3. GRUB_TERMINAL=console
5. update-grub
6. reboot

Taken: http://www.darrinhodges.com/converting-ubuntu-12-04-lts-desktop-to-server/