How to set up SSH to connect on a different port (or a different key)

I was looking for a way to connect via SSH to a git server, on a different port (other than 22), and using a different identity file (see below).

It turns out that the easiest way to do this is by setting up an ssh config file (see man ssh_config), at ~/.ssh/config. Following the directions here, by C. Pino, I included in the the ssh config file:

# ~/.ssh/config
Host my.hostname.com
    Hostname hostname.com
    User git
    Port 55
    IdentityFile ~/.ssh/key_to_use

If you see the error: Bad owner or permissions on /home/jd/.ssh/config, ensure the config file has rw only access for the user (hint from the serverfault.com post here):

$ chown $USER ~/.ssh/config
$ chmod 600 ~/.ssh/config

Different SSH identity files

I decided to go ahead and create different key pairs for each of the online services I use. Using the Github documentation (here), the method I used for each key was:

$ ssh-keygen -t rsa -b 4096 -C "your_email@example.com"
> Generating public/private rsa key pair.

When you're prompted to "Enter a file in which to save the key," press Enter. This accepts the default file location.

> Enter a file in which to save the key (/home/you/.ssh/id_rsa): [enter filename 1 for first keypair]

At the prompt, type a secure passphrase. For more information, see "Working with SSH key passphrases".

> Enter passphrase (empty for no passphrase): [Type a passphrase]
> Enter same passphrase again: [Type passphrase again]

I added the keypair to the ssh-agent, and made sure that the correct keys are referenced in the ssh_config file:

$ eval "$(ssh-agent -s)"
> Agent pid 59566
ssh-add ~/.ssh/filename1

I am now able to connect to my ssh server, on a port other than 22, using a specific identity file, (for git) via:

git clone git@your.hostname.com:path/to/gitfile.git