suryamondal/ssh-and-github

This is all about ssh keys.

SSH Configuration File

The file ~/.ssh/config contains the required information for the SSH to operate smoothly. This file helps

• to establish ssh or rsync without typing password every time
• to establish ssh or rsync from A to B via A->C->D->B in one step
• to push or pull from a remote repository

Check all, then write your own config file. A sample config file also can be found in this repository.

The contents of config

Keeping ssh alive for long time

Is you ssh keep failing when kept idle for long?? The solution is here.

Add the following in the ~/.ssh/config file.

ServerAliveInterval 60

Establish ssh to a public terminal:

The following piece of code goes in the ~/.ssh/config file.

Host remote1
     User myusername
     Hostname host.public.ip.or.url
     IdentityFile ~/.ssh/id_rsa_remote1

The point of all of this is that one can just ssh remote1, instead of ssh [email protected].

Now the ~/.ssh/id_rsa_remote1 file needed to be created.

In simple, a pair of public and private keys are created. The public key is then copied to the remote1 terminal.

Execute the following in a terminal to generate the key,

ssh-keygen -C "my_laptop"

Give the path/to/file as /home/username/.ssh/id_rsa_remote1. Give the full name. It does not resolve ~.

Note: Never keep the passphrase empty. Keep it different than the ssh user password.

Now, copy the public key to the remote1 using the following command.

ssh-copy-id -i ~/.ssh/id_rsa_remote1 remote1

It may ask user password multiple times, don't worry.

After this, whenever you do ssh to remote1, it should not ask for ssh user password. You need to provide the ssh passphrase once after rebooting the terminal.

Establish ssh to a private terminal via public terminal:

local->remote1->remote2

Add the following piece of code in the ~/.ssh/config file.

Host remote2
     User myotherusername
     Hostname host.private.ip.or.url
     IdentityFile ~/.ssh/id_rsa_remote2
     ProxyJump remote1

The ProxyJump does all the magic.

Generate the key in the same way, only change the path to ~/.ssh/id_rsa_remote2.

Then, copy the public key to the remote2 using the following key.

ssh-copy-id -i ~/.ssh/id_rsa_remote2 remote2

It is now done. Do ssh remote2 or rsync remote2:/home/myusername/path/to/file . No need to do it in multiple stages.

For GitHub ( or GitLab or BitBucket)

Add the following piece of code in the ~/.ssh/config file.

Host github.com
     User git
     IdentityFile ~/.ssh/id_rsa_github

Note the user in this case, it is not the github username. Now,

• Generate the id_rsa_github in the same way described above.
• Copy the content (the public key) of id_rsa_github.pub. Go to the Settings->SSH Keys->New SSH Keys and paste it there.
• Last word of the public key is the name of the key (i.e. my_laptop). If you keep the title field empty, github would automatically take the name.
• Test the connection now by using ssh -T [email protected].

If Bitbucket returns the following after an update to OpenSSH 8.8:

Unable to negotiate with <ip address> port <port number>: no matching host key type found. Their offer: ssh-rsa,ssh-dss

then add the following in the config file following IdentityFile .....

     HostKeyAlgorithms +ssh-rsa
     PubkeyAcceptedKeyTypes +ssh-rsa

All set, you may now do push or pull without any headache.

Extra: if you need to access internet via the host

Execute the following in a terminal to create SOCKS tunnel through SSH. This is also called dynamic port forwarding.

ssh -N -D 9050 remote1

Then in the browser, change the SOCKS settings to the following

SOCKS host : 127.0.0.1 port : 9050 SOCKSv5

Now internet should work through SSH.