Linux® Quick Fix

The OpenSSH Secure Copy (SCP) and Secure FTP (SFTP) programs are secure replacements for FTP, and Secure Shell (SSH) is often used as a stealthy alternative to TELNET. OpenSSH isn't limited to Linux; SSH and SCP clients are available for most operati...

Data encryption is accomplished by using special mathematical equations to scramble the bits in a data stream to make it unreadable to anyone who does not have access to the corresponding decryption equation. The process is usually made even harder t...

OpenSSH is installed by default during Linux installations. Because SSH and SCP are part of the same application, they share the same configuration file and are governed by the same /etc/init.d/sshd startup script. You can configure SSH to start at ...

You can test whether the SSH process is running with: [root@bigboy tmp]# pgrep sshd You should get a response of plain old process ID numbers....

The SSH configuration file is called /etc/ssh/sshd_config. By default SSH listens on all your NICs and uses TCP port 22. Take a look at a snippet from configuration: # The strategy used for options in the default sshd_config shipped wit...

Using SSH is similar to TELNET. To log in from another Linux box use the ssh command with a -l to specify the username you wish to log in as. If you leave out the -l, your username will not change. Here are some examples for a server named Smallfry i...

The first time you log in, you get a warning message saying that the remote host doesn't know about your machine and prompting you to store a copy of the remote host's SSH identification keys on your local machine. It will look something like this: ...

If you do decide to deactivate an active TELNET server on Fedora, then use the chkconfig command as detailed in Chapter 16, "TELNET, TFTP, and xinetd." [root@bigboy tmp]# chkconfig telnet off...

In the example below, a user on server Smallfry who needs to know the version of the kernel running on server Bigboy (192.168.1.100) remotely runs the uname -a command. The command returns the version of 2.6.8-1.521 and the server's name, Bigboy: ...

From a networking perspective, FTP isn't very secure, because usernames, passwords, and data are sent across the network unencrypted. More secure forms such as SFTP (Secure FTP) and SCP (Secure Copy) are available as a part of the OpenSSH package tha...

OpenSSH also has the SFTP program, which runs over an encrypted SSH session but whose commands mimic those of FTP. SFTP can be more convenient to use than SCP when you are uncertain of the locations of the files you want to copy, because it has the d...

From time to time you may want to write scripts that will allow you to copy files to a server, or login, without being prompted for passwords. This can make them simpler to write and also prevents you from having to embed the password in your code. ...

Most Linux security books strongly recommend using SSH and SCP over TELNET and FTP because of their encryption capabilities. Despite this, there is still a place for FTP in the world thanks to its convenience in providing simple global access to file...