April 2019
Intermediate to advanced
303 pages
6h 16m
English
Content preview from Cybersecurity Ops with bash
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Chapter 19. Tool: System Availability Monitor
One of the most important jobs of any IT administrator is to maintain the availability of systems. In this chapter, we create a script that uses the ping command to send an alert if a specified system becomes unavailable. Here are the requirements:
-
Read in a file that contains IP addresses or hostnames
-
Ping each of the devices listed in the file
-
Notify the user if a device fails to respond to a ping
Commands in Use
In this chapter we introduce ping for testing if a remote system exists and is responsive.
ping
The ping command uses the Internet Control and Messaging Protocol (ICMP) to determine whether a remote system is available. It is available natively in both Linux and Windows, but they have slight differences. Note that if you are using Git Bash to run ping, it will use the Windows version.
Note
IMCP traffic can be blocked by network firewalls and other devices. If you ping a device and it does not respond, that does not necessarily mean the device is unavailable; it may just be filtering ICMP packets.
Common command options
- -c (Linux)
-
The number of ping requests to send to the remote system
- -n (Windows)
-
The number of ping requests to send to the remote system
- -W (Linux)
-
Time in seconds to wait for a reply
- -w (Windows)
-
Time in milliseconds to wait for a reply
Command example
To ping the host 192.168.0.11 one time:
$ ping -n 1 192.168.0.11 Pinging 192.168.0.11 with 32 bytes of data: Reply from 192.168.0.11: ...
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O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.