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/
  

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  Copy Code