Ssh also provides you with a secure way to transfer your files over the

Internet. The program to use here is scp (Secure Copy). Scp syntax is also

very basic.

scp user@host:filename user@host:filename

To copy a local file to another host using ssh

scp freeos.gif mayank@foo.com:

This will copy the file freeos.gif in the current directory to user mayank

at host foo.com. The ':' at the end of the destination is required because

otherwise scp will copy the file to one named mayank@foo.com.

To copy from a remote host to your local directory

scp mayank@foo.com:freeos.gif .

This will copy the file freeos.gif from user mayank's home directory at

foo.com to the local directory.

There is also a '-r' option for recursive copying of files across directories.

User configuration

The default OpenSSH configuration will work for everyone. You will find

the system wide configuration files in /etc/ssh or if your left it at the

default, in /usr/local/etc. There will be two configuration files here,

ssh_config and sshd_config. The file ssh_config set's the options for the

ssh client program that you will be using. The second file, sshd_config is

the SSH daemon configuration file.

The configuration file for ssh only set the default options for itself.

When a user runs ssh, it first looks at the command line options,

$HOME/.ssh/config followed by /etc/ssh/ssh_config. This allows a user to

put in his own options.

The format of $HOME/.ssh/ssh_config is quite simple. There are quite a few

options here but not all are required.

A simple host entry would be

host foo

compression yes

DSAAuthentication yes

hostname ssh.foo.com

user foo2

IdentityFile [filename]

Each section in the config file starts with a "host" line. Wildcards (*

and ?) are allowed here. A "Host *" would mean that the configuration

below is to be used for all hosts. "Host *freeos.com" is also a valid

entry.

Compression is a good option to give here. In addition to an encrypted

connection, you can also choose to compress the data. This is great over

slower modem links. An additional parameter that you can give after this

is "CompressionLevel". Possible values for this are 1 thru 9 with 1 being

the least level of compression and 9 being the most compression.

DSAAuthentication specifies that you would like to use the more secure DSA