Uptime

Uptime is a measure of the time a computer system has been "up" and running. It came into use to describe the opposite of downtime, times when a system was not operational. For some people, uptime on the server they have access to can be quite important.

To view the uptime of your server, you will need to download a shell client, such as PuTTY. More info is here.

The "uptime" command on Unix systems show the current time, the uptime, the number of users and load averages for the past 1, 5 and 15 minute intervals.

Overview

$ uptime
9:16PM  up 65 days, 15:55, 2 users, load averages: 0.20, 0.21, 0.19

Here is what you will see when you type the uptime command (uptime) into your shell window. You can see:

• The local server time
• The uptime (how long the server has been up without a reboot)
• The number of users connected to the server
• The load averages

Load Average

The system load is a UNIX computing term that describes the amount of work that a computer system is doing. The load average is the system load over a period of time. It is given as three numbers that represent the system load during the last one, five, and fifteen minute periods. So, for the above example, the load averages this minute was 0.20; 5 minutes ago it was 0.21; and 15 minutes ago it was 0.19.

Evaluating the Load Averages

Say the load for your server was at 3.19. This means that the CPU's load was 319%, meaning it was "overloaded" by 219%; as it can only do 100% of the work.

This actually means that this CPU could have handled all of the work scheduled for the last minute if it were 3.19 times faster; so when you think about it, it is best for your server to be under 1.00 so it can keep up.