Installation guide

98 Chapter 9. OpenSSH

ssh penguin.example.net

The ﬁrst time you ssh to a remote machine, you will see a message similar to the following:

The authenticity of host ’penguin.example.net’ can’t be established.

DSA key fingerprint is 94:68:3a:3a:bc:f3:9a:9b:01:5d:b3:07:38:e2:11:0c.

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

Type yes to continue. This will add the server to your list of known hosts as seen in the

following message:

Warning: Permanently added ’penguin.example.net’ (DSA) to the list of known hosts.

Next, you’ll see a prompt asking for your password for the remote machine. After entering

your password, you will be at a shell prompt for the remote machine. If you use ssh without

any command line options, the username that you are logged in as on the local client ma-

chine is passed to the remote machine. If you want to specify a different username, use the

following command:

ssh -l username penguin.example.net

You can also use the syntax ssh username@penguin.example.net.

The ssh command can be used to execute a command on the remote machine without log-

ging in to a shell prompt. The syntax is ssh hostname command. For example, if you want

to execute the command ls /usr/share/doc on the remote machine penguin.example.net,

type the following command at a shell prompt:

ssh penguin.example.net ls /usr/share/doc

After you enter the correct password, the contents of /usr/share/doc will be displayed,

and you will return to your shell prompt.

9.3.2. Using the scp Command

The scp command can be used to transfer ﬁles between machines over a secure, encrypted

connection. It is similar to rcp.

The general syntax to transfer a local ﬁle to a remote system is scp localfile

username@tohostname:/newfilename. The localfile speciﬁes the source, and the

group of username@tohostname:/newfilename speciﬁes the destination.

To transfer the local ﬁle shadowman to your account on penguin.example.net, type the fol-

lowing at a shell prompt (replace username with your username):

scp shadowman username@penguin.example.net:/home/username

This will transfer the local ﬁle shadowman to /home/username/shadowman on

penguin.example.net.

The general syntax to transfer a remote ﬁle to the local system is scp

username@tohostname:/remotefile /newlocalfile. The remotefile speciﬁes the

source, and newlocalfile speciﬁes the destination.

Multiple ﬁles can be speciﬁed as the source ﬁles. For example, to transfer the contents of

the directory /downloads to an existing directory called uploads on the remote machine

penguin.example.net, type the following at a shell prompt:

scp /downloads/* username@penguin.example.net:/uploads/