OpenSSH

 

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Contents

1. Quick Hints
2. Authentication w/Keys
3. ssh-agent
4. OpenSSH Overview

See Also

1. OpenSSH key management

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Quick Hints

 

To log on to another computer:

ssh username@yourhost

 

To copy a file to another computer:

scp filename username@yourhost:/directory/path

or

sftp yourhost

 

To run a command on another computer:

ssh yourhost /path/command

 

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Authentication w/Keys

SSH supports public-key authentication. Here is a procedure to enable public-key authentication for an OpenSSH implementation:

1. Login as user username

2. From the home directory, generate a key pair:

   $ ssh-keygen -t rsa
   Generating public/private rsa key pair.
   Enter file in which to save the key (/usr/local/username/.ssh/id_rsa):
   Enter passphrase (empty for no passphrase):
   Enter same passphrase again:
   Your identification has been saved in /usr/local/username/.ssh/id_rsa
   Your public key has been saved in /usr/local/username/.ssh/id_rsa.pub
   The key fingerprint is:
   05:db:12:51:9f:48:dc:43:cd:8f:22:b0:a7:47:2d:17 username@hostname

   If you leave passphrase blank, you will not be asked for a passphrase later. Though insecure, this is useful for such things as batch ftp programs.

3. Copy the public key to the remote host:

   scp .ssh/id_rsa.pub yourhost:/tmp

4. Log on to your remote host as user username

5. Append the contents of your public key into the SSH authorization file:

   cat /tmp/id_rsa.pub >> .ssh/authorized_keys
   cat /tmp/id_rsa.pub >> .ssh/authorized_keys2

   If the directory and/or file do not exist, create them.

6. Set permissions:

   chmod 755 $HOME/.ssh
   chmod 755 $HOME
   chmod 644 $HOME/.ssh/authorized_keys
   chmod 644 $HOME/.ssh/authorized_keys2

Once authentication w/keys is in place, and if you did not configure a passphrase, you can now run commands such as:

scp filename remotehost:/path/to/remote/directory/
ssh -f remoteserver chmod 666 /path/to/remote/directory/filename

To reset a passphrase, run:

ssh-keygen -p

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