Ssh – How to create alias for ssh command

aliasssh

I have a command, which looks like so:

$ ssh [long list of parameters, eventually I connect to internalhost]

My task is to replace this long list of parameters with just internalhost, so that I could run it like so

$ ssh internalhost

How can I do that?

Best Answer

Standard SSH clients read the configuration files before any connection:

/etc/ssh/ssh_config   # system-wide
~/.ssh/config         # per user

with the latter having more priority.
Ideally, you want to configure the systemwide config with parameters that please all users and the config in your homedir with options specific to you.
Here's an example of ~/.ssh/config

Host remote.example.com
    User            dev1
    IdentityFIle    ~/.ssh/id_rsa_remote

Then to connect:

ssh remote.example.com

Note: ~/.ssh/config must have read/write permissions for the user, and not be accessible by others (chmod 600 ~/.ssh/config)

All possible options are documented in ssh_config manual pages: man ssh_config

Related Solutions

SSH – How to Make SSH Ignore .ssh/config

To make your ssh client ignore your configuration file, use ssh -F /dev/null username@example.com. Because your subnet's IdentityFile is in ~/.ssh/foo rather than ~/.ssh/, you don't need to whip up a whole new file to eschew your extant private key.

From the ssh man page:

 -F configfile
     Specifies an alternative per-user configuration file.  If a
     configuration file is given on the command line, the system-wide
     configuration file (/etc/ssh/ssh_config) will be ignored. The default 
     for the per-user configuration file is ~/.ssh/config.

Bash – Run a command in an interactive shell with ssh after sourcing .bashrc

The problem is that you are trying to run an alias in a non-interactive shell. When you run ssh user@computer command, command is run non-interactively.

Non interactive shells don't read aliases (from man bash):

Aliases are not expanded when the shell is not interactive, unless the expand_aliases shell option is set using shopt (see the description of shopt under SHELL BUILTIN COMMANDS below).

It works if you run it again manually because the final bash command starts an interactive shell so your aliases are now available.

As an alternative, you could launch an interactive shell (bash -i) instead of a simple login shell (bash -l) on the remote machine to run your alias:

ssh user@remote_computer -t 'bash -ic "my_alias;bash"'

This seems a very complicated approach though. You haven't explained why exactly you need to do this but consider these alternatives:

Just start a normal login interactive shell on the remote machine and run the command manually:
```
user@local $ ssh user@remote
user@remote $ my_alias
```
If you always want that alias to be run when you connect to this computer, edit the ~/.profile (or ~/.bash_profile, if present) of the remote computer and add this line at the end:
```
my_alias
```
Because ~/.profile is read each time a login shell is started (so, each time you connect via ssh, for example), that will cause my_alias to be run each time you connect.

Note that by default, login shells read ~/.profile or ~/.bash_profile and ignore ~/.bashrc. Some distributions (Debian and its derivatives and Arch, for example) distributions like Ubuntu have their default ~/.profile or ~/.bash_profile files source ~/.bashrc which means that your aliases defined in ~/.bashrc will also be available in a login shell. This isn't true for all distributions, so you might have to edit your ~/.profile manually to have it source ~/.bashrc. Also note that if ~/.bash_profile exists, ~/.profile will be ignored by bash.

Best Answer

Related Solutions

SSH – How to Make SSH Ignore .ssh/config

Bash – Run a command in an interactive shell with ssh after sourcing .bashrc

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