Novell LINUX ENTERPRISE DESKTOP 10 SP2 - DEPLOYMENT GUIDE 08-05-2008 Deployment Manual page 761

scp also provides a recursive copying feature for entire directories. The command
scp -r src/ sun:backup/ copies the entire contents of the directory src includ-
ing all subdirectories to the backup directory on the host sun. If this subdirectory does
not exist yet, it is created automatically.
The option -p tells scp to leave the time stamp of files unchanged. -C compresses the
data transfer. This minimizes the data volume to transfer, but creates a heavier burden
on the processor.
40.4 sftp—Secure File Transfer
The sftp program can be used instead of scp for secure file transfer. During an sftp
session, you can use many of the commands known from ftp. The sftp program may
be a better choice than scp, especially when transferring data for which the filenames
are unknown.
40.5 The SSH Daemon
(sshd)—Server-Side
To work with the SSH client programs ssh and scp, a server, the SSH daemon, must
be running in the background, listening for connections on TCP/IP port 22. The
daemon generates three key pairs when starting for the first time. Each key pair consist
of a private and a public key. Therefore, this procedure is referred to as public key–based.
To guarantee the security of the communication via SSH, access to the private key files
must be restricted to the system administrator. The file permissions are set accordingly
by the default installation. The private keys are only required locally by the SSH daemon
and must not be given to anyone else. The public key components (recognizable by the
name extension .pub) are sent to the client requesting the connection. They are readable
for all users.
A connection is initiated by the SSH client. The waiting SSH daemon and the requesting
SSH client exchange identification data to compare the protocol and software versions
and to prevent connections through the wrong port. Because a child process of the
original SSH daemon replies to the request, several SSH connections can be made si-
multaneously.
SSH: Secure Network Operations 745