Comp:ssh - Revision history

Gerritg: /* Login without password */

2024-03-01T13:10:13Z

← Older revision		Revision as of 13:10, 1 March 2024
Line 18:		Line 18:
	First generate keys on your local computer:		First generate keys on your local computer:

	ssh-keygen		ssh-keygen -t ed25519 -a 100

	Accept all the defaults by giving <tt>enter</tt> (up to three times).		Accept all the defaults by giving <tt>enter</tt> (up to three times).

Gerritg: Refer to C&CZ wiki

2022-09-18T11:21:06Z

Refer to C&CZ wiki

← Older revision		Revision as of 11:21, 18 September 2022
Line 1:		Line 1:
	With the Linux <tt>ssh</tt> command you can logon to another server. You can configure <tt>ssh</tt> such that you do not have to enter your password every time again.		With the Linux <tt>ssh</tt> command you can logon to another server. You can configure <tt>ssh</tt> such that you do not have to enter your password every time again.

			This is the [https://wiki.cncz.science.ru.nl/SSH C&CZ wiki page on ssh]

	== First make sure ssh is working ==		== First make sure ssh is working ==

Gerritg: /* Login without password */

2022-09-18T11:16:42Z

← Older revision		Revision as of 11:16, 18 September 2022
Line 13:		Line 13:

	== Login without password ==		== Login without password ==
	~~To access servers in the <tt>science.ru.nl</tt> domain follow the "SSH tips and settings"~~
	~~of the C&CZ wiki: [https://wiki.cncz.science.ru.nl/SSH wiki.cncz.science.ru.nl/SSH]~~

	~~An alternative method, which should work with any linux server (not just <tt>*.science.ru.nl</aa> is this:~~

	First generate keys on your local computer:		First generate keys on your local computer:
Line 30:		Line 26:
	You will have to enter your password, but the next time you logon with <tt>ssh</tt> you will not be asked for your password again.		You will have to enter your password, but the next time you logon with <tt>ssh</tt> you will not be asked for your password again.

	'''Warning''': if someone can break into your local computer, they will now also have access to <tt>~~lilo7~~.science.ru.nl</tt>		'''Warning''': if someone can break into your local computer, they will now also have access to <tt>lilo8.science.ru.nl</tt>

			A more secure solution is to protect you private key with a <tt>passphrase</tt>.

	~~A more secure solution is to protect~~ you ~~private key~~ with a <tt>~~passphrase~~</tt>:		The first time you login with <tt>ssh</tt> to a new server you will be asked whether this server should
			be added to the <tt>"~/.ssh/known_hosts"</tt> file. If the operating systems on the server was re-installed you may get a warning suggesting that the server may have been hacked. To prevent these messages follow the
			"SSH tips and settings" of the C&CZ wiki: [https://wiki.cncz.science.ru.nl/SSH wiki.cncz.science.ru.nl/SSH]

	== Using a passphrase and an ssh-agent for security and ease ==		== Using a passphrase and an ssh-agent for security and ease ==

Gerritg: /* Login without password */

2022-09-15T13:45:56Z

← Older revision		Revision as of 13:45, 15 September 2022
Line 13:		Line 13:

	== Login without password ==		== Login without password ==
			To access servers in the <tt>science.ru.nl</tt> domain follow the "SSH tips and settings"
			of the C&CZ wiki: [https://wiki.cncz.science.ru.nl/SSH wiki.cncz.science.ru.nl/SSH]

			An alternative method, which should work with any linux server (not just <tt>*.science.ru.nl</aa> is this:

	First generate keys on your local computer:		First generate keys on your local computer:

Line 19:		Line 24:
	Accept all the defaults by giving <tt>enter</tt> (up to three times).		Accept all the defaults by giving <tt>enter</tt> (up to three times).

	Now copy the local key to the remote server, e.g., to <tt>~~lilo7~~.science.ru.nl</tt>		Now copy the local key to the remote server, e.g., to <tt>lilo8.science.ru.nl</tt>

	ssh-copy-id username@~~lilo7~~.science.ru.nl		ssh-copy-id username@lilo8.science.ru.nl

	You will have to enter your password, but the next time you logon with <tt>ssh</tt> you will not be asked for your password again.		You will have to enter your password, but the next time you logon with <tt>ssh</tt> you will not be asked for your password again.

Gerritg: Add section about rsync command

2022-02-14T14:57:23Z

Add section about rsync command

← Older revision		Revision as of 14:57, 14 February 2022
Line 122:		Line 122:

	ssh cn10 squeue		ssh cn10 squeue

			== The rsync command for copying files and directories over internet ==
			To copy an entire directory from your university account to your PC or laptop with linux
			the <tt>rsync</tt> command is very convenient:

			rsync -avz lilo7.science.ru.nl:projects/stage .

			This will copy the directory <tt>projects/stage</tt> with all its subdirectories and files
			to your current directory, because of the <tt>-a</tt> flag. The <tt>v</tt> flag means
			verbose and the <tt>z</tt> flag means that the files will be compressed during the copy,
			which is useful on slow networks.

			This command also works if a directory with the name <tt>stage</tt> already exists
			in your current directory. In that case, files that are the same on the remote and local
			machine will not be copied. When the remote file is different, a local file with the
			same name will be overwritten.

Gerritg at 20:46, 29 July 2021

2021-07-29T20:46:28Z

← Older revision		Revision as of 20:46, 29 July 2021
Line 108:		Line 108:

	== Keep your session alive ==		== Keep your session alive ==
	You may find that if you haven't used a ssh login session for 10 minutes or so, the connection is lost. This can be prevented by ~~add~~ two lines to your <tt>~/.ssh/config</tt> file:		You may find that if you haven't used a ssh login session for 10 minutes or so, the connection is lost. This can be prevented by adding two lines to your <tt>~/.ssh/config</tt> file:

	Host *		Host *
	ServerAliveInterval 15		ServerAliveInterval 15
	ServerAliveCountMax 3		ServerAliveCountMax 3

	== Use ssh to give remote commands ==		== Use ssh to give remote commands ==

Gerritg: Add session alive configuration

2021-07-29T20:45:37Z

Add session alive configuration

← Older revision		Revision as of 20:45, 29 July 2021
Line 106:		Line 106:

	You can now give command from your local computer directly to cn10:		You can now give command from your local computer directly to cn10:

			== Keep your session alive ==
			You may find that if you haven't used a ssh login session for 10 minutes or so, the connection is lost. This can be prevented by add two lines to your <tt>~/.ssh/config</tt> file:

			Host *
			ServerAliveInterval 15
			ServerAliveCountMax 3

	== Use ssh to give remote commands ==		== Use ssh to give remote commands ==

Gerritg: /* Use ssh to give remote command */

2021-01-27T09:03:41Z

Use ssh to give remote command

← Older revision		Revision as of 09:03, 27 January 2021
Line 104:		Line 104:

	Here <tt>nc</tt> is the ''netcat'' command that is doing the forwarding and 22 is the ssh port number.		Here <tt>nc</tt> is the ''netcat'' command that is doing the forwarding and 22 is the ssh port number.

			You can now give command from your local computer directly to cn10:

			== Use ssh to give remote commands ==
			With ssh you can give commands on the server, e.g.,

			ssh lilo7.science.ru.nl hostname

			Slurm commands (to run batch jobs) must be given from a cluster node, and do not run on, e.g., lilo7. If you have configure ssh as described above, you can check the queue status from your local computer with

			ssh cn10 squeue

Gerritg: /* Configuring ssh */

2021-01-27T08:56:56Z

Configuring ssh

← Older revision		Revision as of 08:56, 27 January 2021
Line 60:		Line 60:

	== Using and ssh-agent ==		== Using and ssh-agent ==
			Start the agent, and give it your passphrase

			eval `ssh-agent`
			ssh-add

			Now see if it works:

			ssh lilo7.science.ru.nl

			The agent remembers your passphrase until you logout. To save some typing, you can define a function in your .bashrc

			function agent () {
			eval `ssh-agent`
			ssh-add
			}

			so you will only have to enter <tt>agent</tt> to start the ssh-agent.

			You can save a few more key-strokes by using the <tt>ssh</tt> configuration file:

			== Configuring ssh ==
			When <tt>ssh</tt> starts it reads the configuration file <tt>~/.ssh/config</tt>

			Add these lines to this file:

			Host lilo7
			Hostname lilo7.science.ru.nl

			If your username is different on <tt>lilo7</tt> you can also add a line, right after Hostname, with

			User username_on_lilo7

			From your local computer, you cannot directly login to a clusternode, e.g., <tt>cn10.science.ru.nl</tt>, you first have to go to a login server (<tt>lilo7</tt> or <tt>lilo6</tt> etc), and from there you can <tt>ssh</tt> to other servers on the network.

			You can configure <ssh> to do this for you. On your local computer, add this to your <tt>~/.ssh/config</tt> file:

			Host cn10
			ProxyCommand ssh -q lilo7 nc -q0 cn10.science.ru.nl 22

			This assumes you have define <tt>lilo7</tt> in the config file as well. You should now be able to directly <tt>ssh</tt> to <tt>cn10</tt> from your local computer:

			ssh cn10

			Here <tt>nc</tt> is the ''netcat'' command that is doing the forwarding and 22 is the ssh port number.

Gerritg: /* Using a passphrase and an ssh-agent for security and ease */

2021-01-27T08:32:50Z

Using a passphrase and an ssh-agent for security and ease

← Older revision		Revision as of 08:32, 27 January 2021
Line 30:		Line 30:

	== Using a passphrase and an ssh-agent for security and ease ==		== Using a passphrase and an ssh-agent for security and ease ==
			Your keys are kept in the .ssh directory in the files, e.g,

			% ls -l ~/.ssh
			-rw------- 1 gerritg gerritg 1766 May 19 2020 id_rsa
			-rw-r----- 1 gerritg gerritg 395 May 19 2020 id_rsa.pub

			The public key <tt>id_rsa.pub</tt> is added to the <tt>authorized_keys</tt> file in the <tt>.ssh</tt> directory on the remote server. Above we used the <tt>ssh-copy-id</tt> command to do that. Before we protect the keys, first remove the keys we just made. On the local computer:

			cd ~/.ssh
			rm id_rsa id_rsa.pub

			and on the remote server (e.g. <tt>lilo7</tt>):

			cd ~/.ssh
			rm authorized_keys

			If you have more than one key in <tt>authorized_keys</tt> use an editor to remove keys.

			Now, on your local computer re-generate the keys

			ssh-keygen

			Accept the default file <tt>.ssh/id_rsa</tt> with <tt>Enter</tt>, and then enter a passphrase.

			Now copy your public key again to <tt>lilo7</tt> with the <tt>ssh-copy-id</tt> command, and try <tt>ssh</tt> to <tt>lilo7</tt>.
			Instead of your password, you will now have to enter your passphrase. Even if you passphrase is the same as your password, this is more secure, because your passphrase will never leave you computer. However, you will now have to re-enter your passphrase every time you logon.

			The next step is to use an <tt>ssh-agent</tt> to remember your passphrase until you logout, so you don't have to enter it too often.

			== Using and ssh-agent ==