Basic Usage

Generate Key Pair

ssh-keygen -t dsa -b4096

Exchange Key

scp ~/.ssh/id_dsa.pub [email protected]:.ssh/authorized_keys

If you have ssh-copy-id installed, you can just run

ssh-copy-id [email protected]

Login Remote Instance

After puting your public keys in remote instance, then you can run:

ssh [email protected]

to login remote instance

Excute Cammand On Remote Host

ssh [email protected] ls -l /

Using Scp

Local to remote

scp [email protected]:

Remote to local

scp [email protected]:report.docreport.doc

Test Connection

ssh-T git@host-v

Server Configurations

将PasswordAuthentication no加入server的/etc/ssh/sshd_config来阻止使用密码ssh登陆

通过Port 4444来使用自定义端口

限定用户AllowUsers user1 user2

限定用户组AllowGroups sshmembers

Disable root loginPermitRootLogin no

Client Configuration

Ssh client configuration lies in~/.ssh/config

Example common settings like followings:

Host github-default

HostName github.com

User username

IdentityFile ~/.ssh/gitkey_default

Host

Only the host of the ssh command match this value, will the following rule applied to this command HostName The real hostname the command will try to connect

Username

The real Username the command will use

IdentityFile

Location of the private key

For other configuration, please refer to ssh man page

Reuse Session & Tunel

Host *

ControlMaster auto

ControlPath ~/.ssh/sockets/%r@%h-%p

ControlPersist 600

ControlMaster auto

The ControlMaster option is one of SSH's best kept secrets. It instructs SSH to reuse an existing connection to the server if it already exists. This means that, if you run sshexample.com, open another terminal, and run sshexample.comthere, the two sessions will be transported over the same underlying connection. The second session starts much more quickly because the SSH handshake has already been completed.

ControlPath ~/.ssh/sockets/%r@%h-%p

ControlPath is a specification of where to create the control socket on your filesystem. If you use the value provided here, make sure to manually mkdir ~/.ssh/sockets. At any time, you can manually remove the control socket (using plain-old rm), and the next ssh invocation will establish a new connection. This is especially useful if you've recently reopened your laptop and your SSH connections haven't yet figured out that the server terminated them.

ControlPersist 600

Without ControlPersist, once the first SSH session you open is closed, all other sessions on that connection are closed as well. This can lead to a variety of surprising behavior: if you exit the initial SSH shell while other sessions are sharing the connection, the process will just hang. If you send it a Ctrl-C, all of those other sessions will be abruptly terminated.

Further Use

Set Tunnel From Local To Remote Server

ssh -i key -f -N -L 8888:example.com:80 username@remote_host

Pattern

ssh -i key -f -N -L your_port:site_or_IP_to_access:site_port username@host

-f options let SSH to go into the background before executing

-N options let SSH not open a shell or execute a program on the remote side

When you visit 127.0.0.1:8888 on your local computer, then you will go through the tunnel and access the example.com:80 via your remote computer

Set Tunnel From Remote To Local

ssh -f -N -R 8888:example.com:80 username@remote_host

Pattern

ssh -R remote_port:site_or_IP_to_access:site_port username@host

When you visit 127.0.0.1:8888 on your remote computer, then you will go through the tunnel and access the example.com:80 via your local computer

Set Dynamic Tunneling to a Remote Server

ssh -f -N -D 7777 username@remote_host

From here, you can start pointing your SOCKS-aware application (like a web browser), to the port you selected. The application will send its information into a socket associated with the port.

The method of directing traffic to the SOCKS port will differ depending on application. For instance, in Firefox, the general location is Preferences > Advanced > Settings > Manual proxy configurations. In Chrome, you can start the application with the --proxy-server= flag set. You will want to use the localhost interface and the port you forwarded.

ProxyCommand

Some times you will protect your servers behind a bastion instance, or event 3 or 4 layers like following:

If you want ssh onto internal instances, you need jump from bastion and then do another ssh command.

It's not fancy isn't it? It`s time to embrace proxy command. You can just run command as followings:

ssh -o ProxyCommand='ssh -W 10.0.1.1:22 [email protected]' [email protected]

It will setup a tunnel forward socket from local to internal via bastion, and then you [email protected], it will be forwarded to the internal instances.

Done.

Conclusion

Let just use the former problem as an example we can set our ssh configuration file like this

Host */*