SSH

Troubleshooting for common SSH issues

Permissions

Set the permissions of directories, keys and config file to the following numeric codes using chmod.

Item	Sample	Numeric	Bitwise
SSH folder	~/.ssh	700	drwx------
Public key	~/.ssh/id_rsa.pub	644	-rw-r--r--
Private key	~/.ssh/id_rsa	600	-rw-------
Config	~/.ssh/config	600	-rw-------
Home folder	~	755 at most	drwxr-xr-x at most

Or simply run:

chmod 700 $HOME/.ssh
chmod 600 $HOME/.ssh/*
chmod 644 $HOME/.ssh/*.pub

Repeat login

When logging into the zervers, you login twice:

1. Once on the bastion server
2. and another time to access an internal server (i.e. z011, z012 … z014)

This can be reduced to just one login by setting up SSH key authentication between our client and the internal servers.

Generate key pair

On your client machine, run ssh-keygen. Give the identity file pair a custom name (e.g. ‘zervers’). Do not set a passphrase for the key file.

ssh-keygen -t ed25519 -a 100 -f ~/.ssh/zervers

Send public key file to internal server

ssh-copy-id -i ~/.ssh/zervers USERNAME@HOSTNAME

This adds your public key to the ~/.ssh/authorized_users file on the remote machine.

Edit your ssh config

On you client machine edit the ssh config file.

vim ~/.ssh/config

Add the following line to the indicated host in your ssh_config file.

Host z010 z011 z012 z013 z014
    # previous config options ...
    IdentityFile ~/.ssh/zervers

Test it out

Now when you log in to the zervers, you should only have to login once!

ssh HOSTNAME

Note

If you access multiple servers frequently (e.g. z014 & z010), you will have to repeat this process for each machine.