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This article mainly introduces how to use the SSH command under Linux, has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let the editor take you to understand.

1. View the SSH client version

Sometimes you need to confirm the SSH client and its corresponding version number. You can get the version number using the ssh-V command. It is important to note that Linux generally comes with OpenSSH: the following example shows that the system is using OpenSSH:

$ssh-V

OpenSSH_3.9p1, OpenSSL 0.9.7a Feb 19 2003

The following example shows that the system is using SSH2:

$ssh-V

Ssh: SSH Secure Shell 3.2.9.1 (non-commercial version) on i686-pc-linux-gnu

2. Log in to the remote host with SSH

When you log in to a remote host using ssh for the first time, a message appears that the host key is not found. After typing "yes", the system will add the key of the remote host to .ssh / hostkeys in your home directory, so you can continue. Examples are as follows:

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Localhost$ ssh-l jsmith remotehost.example.com

Host key not found from database.

Key fingerprint:

Xabie-dezbc-manud-bartd-satsy-limit-nexiu-jambl-title-jarde-tuxum

You can get a publickey's fingerprint by running% ssh-keygen-F publickey.pub on the keyfile.

Are you sure you want to continue connecting (yes/no)? Yes

Host key saved to / home/jsmith/.ssh3/hostkeys/key_22_remotehost.example.com.pub hostkey for remotehost.example.com

Accepted by jsmith Mon May 26 2008 16:06:50-0700 jsmith@remotehost.example.com password: remotehost.example.com$

Because the key of the remote host has been added to the list of known hosts of the ssh client, when you log in to the remote host for the second time, you only need to enter the login password of the remote host.

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Localhost$ ssh-l jsmith remotehost.example.com

Jsmith@remotehost.example.com password:

Remotehost.example.com$

For various reasons, the key of the remote host may change after you log in for the first time, and you will see some warning messages. There may be two reasons for this:

O the system administrator upgraded or reinstalled the SSH server on the remote host.

O someone is doing some malicious acts, and so on.

Before you type "yes", the best option may be to contact your system administrator to analyze why the host CAPTCHA has changed and check that the host CAPTCHA is correct.

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Localhost$ ssh-l jsmith remotehost.example.com

@

@ WARNING: HOST IDENTIFICATION HAS CHANGED!

@ @

IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!

Someone could be eavesdropping on you right now (man-in-the- middle attack)!

It is also possible that the host key has just been changed.

Please contact your system administrator.

Add correct hostkey to-/ home/jsmith/.ssh3/hostkeys/key_22_remotehost.example.com.pub to get rid of this message.

Received server key's fingerprint:

Xabie-dezbc-manud-bartd-satsy-limit-nexiu-jambl-title-arde-tuxum

You can get a publickey's fingerprint by running% ssh-keygen-F publickey.pub on the keyfile.

Agent forwarding is disabled to avoid attacks by corrupted servers.

Are you sure you want to continue connecting (yes/no)? Yes

Do you want to change the host key on disk (yes/no)? Yes

Agent forwarding re-enabled.

Host key saved to / home/jsmith/.ssh3/hostkeys/key_22_remotehost.example.com.pub hostkey for remotehost.example.com

Accepted by jsmith Mon May 26 2008 16:17:31-0700 jsmith @ remotehost.example.com's password: remotehost$

3. Debug SSH client session

When there is a problem with the ssh connection, we need to locate these errors by looking at the debugging information. Generally speaking, you can view debugging information by using the v option (note: it is lowercase v).

Examples of no SSH client debugging information:

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Localhost$ ssh-l jsmith remotehost.example.com

Warning: Connecting to remotehost.example.com failed: No address associated to the name

Examples that contain ssh debugging information:

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Locaclhost$ ssh-v-l jsmith remotehost.example.com

Debug: SshConfig/sshconfig.c:2838/ssh3_parse_config_ext:

Metaconfig parsing stopped at line 3.

Debug: SshConfig/sshconfig.c:637/ssh_config_set_param_verbose:

Setting variable climbing / climbing / climbing Mode' to FALSE'.

Debug: SshConfig/sshconfig.c:3130/ssh_config_read_file_ext: Read 17 params from config file.

Debug: Ssh3/ssh3.c:1707/main: User config file not found, using defaults. (Looked for / home/jsmith/.ssh3/ssh3_config')

Debug: Connecting to remotehost.example.com, port 22... (SOCKS not used)

Warning: Connecting to remotehost.example.com failed: No address associated to the name

[note: in many commands, the v option corresponds to verbose, which means detailed information.]

When you log in to the remote host from the local computer using ssh, you may want to switch to the local computer to do something, and then go back to the remote host. At this point, you don't need to break the ssh connection, just follow the steps in point 4:

4. Switch the SSH session with the SSH exit character

This technique is very practical. In particular, remote login to a host A, and then login from A to B, if you want to do some operations on A, you have to open another terminal, which is very troublesome.

When you log in to the remote host from the local computer using ssh, you may want to switch to the local computer to do something, and then go back to the remote host. At this time, you don't need to break the ssh connection, just follow the steps below:

When you have logged in to the remote host, you may want to go back to the local host to do something, and then continue back to the remote host. In this case, there is no need to disconnect the session of the remote host, you can do this in the following ways:

1. Log in to the remote host:

Localhost$ ssh-l jsmith remotehost

two。 Connected to the remote host:

Remotehost$

3. To temporarily return to the local host, enter the exit symbol: "~" combined with "Control-Z".

When you type "~" you will not immediately see it on the screen, but will not display together until you press and press enter. Enter "~" on the remote host as follows

Remotehost$ ~ ^ Z

[1] + Stopped ssh-l jsmith remotehost

Localhost$

4. Now that you have returned to the local host, the ssh remote client session is running in the UNIX background, and you can view it as follows:

Localhost$ jobs

[1] + Stopped ssh-l jsmith remotehost

5. You can switch the ssh session process running in the background to the foreground and return to the remote host without entering a password

Localhost$ fg 1

Ssh-l jsmith remotehost

Remotehost$

5. Use SSH to exit the character session and display the information

To get some useful information about the current session, you can do it in the following ways. However, this can only be used on SSH 2 clients.

Log in to the remote server

Localhost$ ssh-l jsmith remotehost

On the remote server, enter the ssh exit character ~ and enter s as shown below. This will show a lot of useful information about the current ssh connection

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Remotehost$ [Note: when you type ~ s on the command line, it is not visible.]

Remotehost: remotehost

Localhost: localhost

Remote version: SSH-1.99-OpenSSH_3.9p1

Local version: SSH-2.0-3.2.9.1 SSH Secure Shell (non-commercial)

Compressed bytes in: 1506

Uncompressed bytes in: 1622

Compressed bytes out: 4997

Uncompressed bytes out: 5118

Packets in: 15

Packets out: 24

Rekeys: 0

Algorithms:

Chosen key exchange algorithm: diffie-hellman-group1-sha1

Chosen host key algorithm: ssh-dss

Common host key algorithms: ssh-dss,ssh-rsa

Algorithms client to server:

Cipher: aes128-cbc

MAC: hmac-sha1

Compression: zlib

Algorithms server to client:

Cipher: aes128-cbc MAC: hmac-sha1

Compression: zlib

Localhost$

Thank you for reading this article carefully. I hope the article "how to use SSH commands under Linux" shared by the editor will be helpful to everyone. At the same time, I also hope you will support us and pay attention to the industry information channel. More related knowledge is waiting for you to learn!

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