Mastering UNIX® Shell Scripting: Bash, Bourne, and Korn Shell Scripting for Programmers, System Administrators, and UNIX Gurus, Second Edition

CHAPTER23

Creating a System-Configuration Snapshot

Have you ever rebooted a system and it came up in an unusual state? Any time that you reboot a system, you run a risk that the system will not come back up properly. When problems arise it is nice to have before and after pictures of the state of the machine. In this chapter we are going to look at some options for shell scripts that execute a series of commands to take a snapshot of the state of the machine. Some of the things to consider for this system snapshot include filesystems that are mounted, NFS mounts, processes that are running, network statistics and configuration, routing tables, and a list of defined system resources, just to name a few. This is different from gathering a snapshot of performance statistics, which is gathered over a period of time. All we are looking for is system-configuration data and the system's state at a point in time, specifically before the system is rebooted or when it is running in a normal state with all of the applications running properly.

With this information captured before a system reboot, you have a better chance of fixing a reboot problem quickly and reducing down time. I like to store snapshot information in a directory called /usr/local/reboot with the command names used for filenames. For this shell script all of the system information is stored in a single file with a section header added for each command output. Overall, this is not a difficult shell script to write, but gathering ...