Linux – How to determine if I’m logged in via SSH

linuxshellssh

I'm currently setting up a fairly complex bash configuration which shall be used on multiple machines. I try to find out if it is possible to determine whether I'm logged in via SSH or on a local machine. This way I could, for instance, set some aliases depending on that fact. Like aliasing halt to restart since stopping a remote server might not be the best thing to do.

What I know so far is, that the environment variable SSH_CLIENT is set when I logged in via ssh. Unfortunately, this variable is discarded when I start a super user shell with sudo -s. I also know that I can pass a parameter to sudo that instructs sudo to copy all my environment variables to the new shell environment, but if I don't want to do this, is there an other way?

Best Answer

You could use "w" or "who" command output. When you connect over ssh, they'll show your source IP.

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Linux Bash – How to Sort du -h Output by Size

As of GNU coreutils 7.5 released in August 2009, sort allows a -h parameter, which allows numeric suffixes of the kind produced by du -h:

du -hs * | sort -h

If you are using a sort that does not support -h, you can install GNU Coreutils. E.g. on an older Mac OS X:

brew install coreutils
du -hs * | gsort -h

From sort manual:

-h, --human-numeric-sort compare human readable numbers (e.g., 2K 1G)

Ssh – How to automate SSH login with password

Don't use a password. Generate a passphrase-less SSH key and push it to your VM.

If you already have an SSH key, you can skip this step… Just hit Enter for the key and both passphrases:

$ ssh-keygen -t rsa -b 2048
Generating public/private rsa key pair.
Enter file in which to save the key (/home/username/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/username/.ssh/id_rsa.
Your public key has been saved in /home/username/.ssh/id_rsa.pub.

Copy your keys to the target server:

$ ssh-copy-id id@server
id@server's password:

Now try logging into the machine, with ssh 'id@server', and check-in:

.ssh/authorized_keys

Note: If you don't have .ssh dir and authorized_keys file, you need to create it first

to make sure we haven’t added extra keys that you weren’t expecting.

Finally, check to log in…

$ ssh id@server

id@server:~$

You may also want to look into using ssh-agent if you want to try keeping your keys protected with a passphrase.

Best Answer

Related Solutions

Linux Bash – How to Sort du -h Output by Size

Ssh – How to automate SSH login with password

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