OPS245 Lab 8 Newversion

The server concept

For most people a server is something on the internet you connect to, and a client is something you connect from. That sort of view is mostly valid, but it breaks down a little when the server and the workstation are the same machine.

A couple of examples:

• When you connect to wiki.littlesvr.ca in Firefox:
  • Firefox is the client, it's making the request for a web page
  • The web server (Apache) on wiki.littlesvr.ca is the server, responding the the request with the contents of the web page
• When you use your phone to check your school email:
  • The email application on your phone is the client, making the request to get new email
  • The school email server (e.g. Postfix, Gmail, Office365) is the server, responding to the request with a list of new emails

Most of a Linux system administrator's work is done in a terminal, and most of that is done on remote machines. Few companies can afford to hire in-house administrators, and those that can afford it have too many machines to connect keyboards and monitors to. But everything is connected to a network.

The same client-server model applies here. You connect from a terminal on your workstation to the machine you want to work with. In this case:

• The ssh program is the client, connecting to the ssh server, sends what you type to the server and prints the output which those commands print on the server.
• The ssh server (sshd) is the software on the destination machine which receives commands from the client, executes them, and sends the output of those commands back to the client.

Also

• Create an account on ops345.ca for ssh practice
• The "server" concept
• Using ssh to control a remote Linux server
• Remote credentials don't need to match local credentials
• Permissions work the same way, they apply to the user who is logged in
• Practice with permissions on files you own and files you don't own
• Copy files between Linux machines using scp
• Copy directories
• Note how ownership applies to files transferred between systems