SSH

I use SSH all the time for work and my own projects. This post is just a collection of SSH related commands that I find useful.

Basic Usage

Log into a machine as a specific user with ssh.

  ssh username@example.com

Specify a port other than the default (22) with -p.

  ssh username@example.com -p 5555
  ssh ssh://username@example.com:5555

Specify a SSH key with -i followed by the path to the key.

  ssh -i ~/.ssh/my_key  username@example.com

Copy Files

SCP

I occasionally use scp to copy files over the network (but I usually use SFTP)

scp -P 5555   -i ~/.ssh/my_id  <FILE_NAME> username@example.com:/home/username/<FILE_NAME> 

Note:

• For scp the port option -P is upper case P. This is different from ssh which uses lower case p.
• -i is still the same.

To copy an entire folder use the -r option

scp -r host:path/directory .

SFTP

sftp lets you interactively copy files to and from a server.

sftp -oPort=5555   -i ~/.ssh/my_id  username@example.com

The basic commands are:

• pwd : Show the name of the remote working directory.
• ls : list the contents of the remote directory.
• cd <path> : Change the remote directory to`
• put <filename> : Upload a local file to the remote machine
• get <filename> : Download a remote file to the local machine. adding -r will recursively copy files from the server.
• lpwd : Show the name of the local working directory.
• lls : list the contents of the local directory.
• lcd <path> : Change the local directory to`

Generate SSH Keys

Use ssh-keygen to create SSH keys.

ssh-keygen -t rsa

-t rsa sets the algorithm to RSA. You can set the number of bytes (more is better) with the -b option

ssh-keygen -t rsa -b 4096

You will be asked for a passphrase. I typically enter one, but you can just press return to leave it blank:

fred5617@homebox:~$ ssh-keygen -t rsa
Generating public/private rsa key pair.
Enter file in which to save the key (/home/fred5617/.ssh/id_rsa): /home/fred5617/.ssh/id_rsa_eraseme
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /home/fred5617/.ssh/id_rsa_eraseme
Your public key has been saved in id_rsa_eraseme.pub
The key fingerprint is:
SHA256:XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX fred5617@homebox
The key's randomart image is:
+---[RSA 3072]----+
|.XXXXXXXXXX      |
|= XXX.XXX. XXX X |
|-XXX X X XXXXX   |
|  .X. XX. XX     |
|     XXXA.       |
|    , .XX      * |
|   XX . X        |
|   * >.XX .      |
|       * X XX    |
+----[SHA256]-----+

Copy SSH keys to a Server

Once you have a new key, you can upload its public key to a server with ssh-copy-id.

ssh-copy-id -i ~/.ssh/id_rsa_eraseme  fred@example.com

For this to work, you must already have SSH and password access to the server.

ssh-agent

Sometimes you want to use SSH multiple times without entering your passphrase each time. To do this, use ssh-agent.

eval $(ssh-agent)

Then add the key you want to use with ssh-add

ssh-add /path/to/id_rsa_eraseme

SSHFS

Mounting a remote filesystem with sshfs

sshfs fred5617@10.10.50.1:/home/fred5617/SEGA/sgdkrocksnet  ~/sgdkrocksnet/