2021-12-25 15:55:56 +01:00
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# General
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The basic syntax is
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```
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ssh user@domain
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```
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You can either log in using a password or an ssh key.
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The second method is considered safer and more user friendly.
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To initialize the ability to log in using an ssh key, you need a local ssh key-pair.
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If you dont have one, generate one on your local machine using
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```
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ssh-keygen -t rsa
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```
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and following the instructions.
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This generated a public and private key pair which are saved in `~/.ssh`.
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To then enable the key based login, you have to make sure that `~/.ssh` exists on the server.
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Change the permisions of this folder using `chmod 700 ~/.ssh`.
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The next step is to make the `authorized_keys` file using
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```
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touch ~/authorized_keys
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2022-01-02 09:57:02 +01:00
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chmod 600 ~/.ssh/authorized_keys ```
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2021-12-25 15:55:56 +01:00
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Now open the `authorized_keys` and copy-paste the public key contents in to it.
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One can also use `ssh-copy-id user@domain` after generating the key-pair.
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## Add keys to Keychain
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If you added a passphrase to your key, you may be tired of typing it over and over again.
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Add the following to your `~/.ssh/config`.
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```
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Host HOME
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User root
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HostName domain.example
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IdentityFile ~/.ssh/id_rsa
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AddKeysToAgent yes
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UseKeychain yes
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```
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This saves the passphrase in the keychain for the current session.
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It also allows you to specify which specific key to use and to use `ssh HOME` to connect to the server.
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## Add keys for layered logins
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If you need to connect to an access server before connecting to the actual server you want to connect to, this can be automized by adding
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```
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IgnoreUnknown AddKeysToAgent,UseKeychain
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## All EXEMPLUM-COMPANY
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Host EXEMP*
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User username
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IdentityFile ~/.ssh/id_rsa
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AddKeysToAgent yes
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UseKeychain yes
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## Access server
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Host EXEMPaccess
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HostName login.example.com
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## Working server
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Host EXEMPwork
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HostName work.example.com
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proxycommand ssh -CW %h:%p EXEMPaccess ## access server
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```
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to your `~/.ssh/config`.
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To connect to the working server, just type `ssh EXEMPwork`.
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