I manage too many remote servers to be able to remember their IP addresses, usernames and passwords. The key to simplify this experience is a proper SSH configuration. By adjusting
.ssh/config file you can easily create a memorable alias, along with particular settings for any server you use.
Use public/private key authentication to avoid entering password each time you connect to the server. Create an alias for each server within
.ssh/config using the syntax below
Host alias-name HostName my.realm.com/or-ip User zaiste
and connect to it like so
λ ssh alias-name
Public/Private Key Authentication
When you connect to a remote server you must enter a password in order to authenticate yourself. This step, however, can be easily avoided using public/private key authentication. The setup is pretty straightforward. First of all, you have to generate a public/private key pair:
λ ssh-keygen -t rsa -C '<your email>'
It is a good idea to choose a strong password. If you want to change the password for a specific key use
-p option. Additionaly a
-f option can be use to specify a key file to use.
Next, copy the content of
.ssh/id_rsa.pub file and add it to
.ssh/authorized_keys on a remote server which you want to connect with. If the file (or directory) doesn't exist, simply create it. Now you should be able to connect to that server without entering your password
λ ssh email@example.com
It is also a good idea to have multiple keys, separated for each remote place or keys used with a specific group e.g. private, client specific, etc. This enhances the security in case any of the authentication key pairs are compromised.
Let's make now a server alias, so we don't have to remember entire domain name or IP address each time we want to connect to it. Open your
.ssh/config and add something like this.
Host my HostName my.realm.com User zaiste
Don't forget to adjust it for your case.
Such configuration will reduce ssh invocation to the following line
λ ssh my
For each entry you can adjust connection settings like port number or which private key to use. Take a look at SSH documentation for possible options
Specifing Private Key
By default for each server the same key pair is used. In order to change this behaviour we have to use
IdentityFile option which specifies a private key to use for authentication with the given host, e.g.
Host client HostName client.server.com User p45dazz IdentityFile ~/.ssh/client.key
This can be pretty useful when you are working within different organization on GitHub.
Host ghn User git HostName github.com IdentityFile ~/.ssh/nukomeet.key
With such entry I can now clone from a specific organization using even more succinct command
λ git clone ghn:nukomeet/some_repository.git
For security reason, you can leave only a limited number of open ports (on the server which you have control of), e.g
80/443 for web and
22 for SSH. Now, In order to connect to specific services, we can simply tunnel them using the following command:
λ ssh -f -N -L 9906:127.0.0.1:27017 firstname.lastname@example.org
It means that a remote port number
27017 (MongoDB server) is mapped to a local port
9906. Now, by connecting to
localhost:9906 you will have access to a remote MongoDB server. There are two additional options
-f which puts ssh in background and
-N which does not execute a remote command. As before, if you use such command frequently, it can be saved to
.ssh/config like so:
Host tunnel HostName db.example.com IdentityFile ~/.ssh/zaiste.key LocalForward 9906 127.0.0.1:27017 User zaiste
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