I'd like to take a moment to share a few ways I use ~/.ssh/config file to make my life happier every day.
With these options I never need to remember host names, usernames, or port numbers, and the vast majority of my SSH commands look like:
$ ssh myapp $ ssh myclient-prod-db $ rsync -a app-backup:backups/jan01 .
Every time I get ssh access to a server I add an entry to my config file giving the host a name that's meaningful to me (for example, "someclient-server" or "myproj-backup") and setting the default username and port:
Host someclient-dev
Hostname 11.22.33.44
User dev
Host someclient-prod-app
Hostname redbunny.myclient.com
Port 4242
User prod
Host someclient-prod-db
Hostname bluefish.myclient.com
Port 4242
User db
These host alias can be used just about everywhere a hostname is passed to SSH, including:
SSH from the command line:
$ ssh someclient-dev ... dev@11.22.33.44 $
git, mercurial, or other version control systems:
$ git remote add dev someclient-dev:repo/
rsync:
$ rsync -a media/ someclient-dev:media/
Not only does this mean I never need to remember weird hostnames or arbitrary usernames, but I can also open the file to see a list of all the machines I've ever had access to (which can be very useful when an old machines needs work done).
The bash-completion package is even .ssh/config aware, so tab completion will work as expected:
$ ssh someclient-<tab> someclient-dev someclient-prod-app someclient-prod-db
Amazon EC2 key management is also a huge continence. Each time I get access to an Amazon EC2 instance I add the IdentityFile to the Host definition:
Host *.amazonaws.com
User ec2-user
Host myapp
Hostname ec2-1-2-3-4.compute-1.amazonaws.com
IdentityFile ~/.ssh/aws-myapp.pem
As above, this will create the host alias myapp, and the identify file ~/.ssh/aws-myapp.pem will be used to connect (no more -I flag on the command line).
Finally, there are a few options that are useful to set for all hosts:
Host *
# Instead of just printing the host key fingerprint as an opaque hex
# string, print a pretty art. Ostensibly this is for security, but
# mostly it's pretty:
# +--[ RSA 2048]----+
# | oE .. |
# | .. ... |
# | . ooo |
# | oooooo |
# | . =+.+S+ |
# | o.+o.o.. |
# | o.. |
# +-----------------+
VisualHostKey yes
# Send explicit keepalive packets. This isn't often a problem, but I've
# run into a few combinations of network and machine that will drop
# inactive connections.
KeepAlive yes
ServerAliveInterval 60
# SSH Agent Forwarding is described here:
# http://www.unixwiz.net/techtips/ssh-agent-forwarding.html
ForwardAgent yes
# SSH Control Channels allow multiple SSH sessions to share one
# connection. For example, the first time I run "ssh myapp", ssh will
# create a new connection to the server (creating a TCP connection,
# authenticating, etc). As long as that connection
# is active, though, running "ssh myapp" from another terminal will
# re-use the same TCP connection, authentication, etc, making the
# command virtually instant.
# Note that the ControlPersist option is important, otherwise all the
# sessions will be disconnected when the master session closes.
ControlPath ~/.ssh/control/master-%l-%r@%h:%p
ControlMaster auto
ControlPersist 60