Bash – Executing a remote command

awsbashlinuxremotessh

I can't edit the .bashrc of the fs I'm connecting to
I have to use the ~/.ssh/config file

Here is my current config:

Host my-ssh
HostName <ip>
User <user>
IdentityFile <file location>
Compression yes
RemoteCommand cd <path to folder>

When I run ssh my-ssh nothing happens. The connection seems to automatically close. If I remove the RemoteCommand line it connects without an issue.

Is this something on the server config? It's an EC2 instance, either CentOS or RHEL and bash is the shell.

Best Answer

If you specify a remote command, then the ssh connection is going to close as soon as the remote command exits. A cd command will exit almost immediately.

A common way to do what you want is:

RemoteCommand cd /some/path && bash

(Substitute your desired shell in place of "bash"). This cd's to the path and then invokes a subshell if the cd operation succeeded. The ssh connection will close when the subshell exits.

You will also want to force ssh to allocate a PTY for the session:

RequestTTY yes

If you don't, then ssh won't request one by default, and you'll get a non-interactive shell session. Notably, you won't get a command prompt.

Related Solutions

Ssh – Multiple ‘Host *’ in ssh_config

From the ssh_config manual:

Since the first obtained value for each parameter is used, more host-specific declarations should be given near the beginning of the file, and general defaults at the end.

So in your example, all hosts will use User harleypig and IdentityFile ~/.ssh/personal_id_rsa.

Think of Host directives with wildcards as fallbacks: use the following settings only if they haven't been set yet. You need to write something like this:

Host host1
Hostname host1.com
Host host2
Hostname host2.com
Host host*
User harleypig
IdentityFile ~/.ssh/personal_id_rsa

You can put multiple patterns on a Host line if a given set of host aliases can't be matched with wildcards, e.g. Host host* more* outlier.

Ssh – Determine the target of an SSH connection at runtime

Since you don't pass a command to ssh, it runs a shell, which expects commands on its standard input. But you aren't passing it shell commands, you're passing it SSH traffic. Hilarity ensues.

Tunnelling is the whole point of ProxyCommand. This example tunnels an SSH connection inside an SSH connection. If you don't want to tunnel, ProxyCommand is not what you're looking for.

Since OpenSSH 6.4, you can use a Match directive with the exec keyword to include blocks conditionally based on a run-time directive. A typical use case is to have different actual host names or proxy commands depending on where your laptop is. Each Match block replaces a Host block, and you can't use the output of the command to determine the host name, only the fact that it exited with status 0.

# Connection inside ACME network
Match host foo exec on-acme-network
HostName foo.acme.local

# Connection from outside ACME
Host foo
HostName foo.example.com

Proxying is another option. To make a connection to a host name and port that are determined at connection time, you can use netcat to set up the TCP connection.

Host foo
ProxyCommand nc $(determine-target-host-name) 22

If you want a fully dynamic .ssh/config, you can make it a named pipe and ensure that a process is always writing to it. Or put it on scriptfs.

Best Answer

Related Solutions

Ssh – Multiple ‘Host *’ in ssh_config

Ssh – Determine the target of an SSH connection at runtime

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