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=== Part 1: Hard Disk Space Utilities===
Another essential duty of a Linux system administrator is to anticipate problems and take preventative measures to avoid computer system problems <u>before</u> that occur. An example could be to periodically monitor hard disk space for potential low availability in order to make adjustments before it impacts on system performance.
'''Perform the following steps:'''
# Remain in Launch your '''c7host''' and '''centos2''' VMs.# Switch to your '''centos2''' VM for this sectionmachine.# Open a terminal, and login as '''root'''.
# Issue the command: <b><code><span style="color:#3366CC;font-size:1.2em;">df -h</span></code></b>
# Note the disk space usage for the '''/''', and '''/home''', and '''/archive''' partitions.
# If a partition is running out of available space, the Linux System Administrator can reallocate space among partitions or add another disk and grow the file system (like you did in a previous investigation). The administrator also can investigate the cause of low disk space. Two examples immediately come to mind: excessive use of space from users, and potential penetration from hackers.
# To investigate excessive disk usage by regular users, you can obtain a total amount of disk usage for that user by issuing the command:<br><b><code><span style="color:#3366CC;font-size:1.2em;">du -hs /home/regularuseridhsa .</span></code></b># To provided a more detailed list of usage (file-by-file), issue the command:<br><b><code><span style="color:#3366CC;font-size:1.2em;">du -h /home/regularuserid ha . | more</span></code></b>
# If there is a recurring space usage problem with regular users, the Linux system administrator can impose quotas (caps on disk usage). This method is not taught in this course.
# The methods to monitor potential penetration to a Linux system are too numerous, and are taught in other coures courses (for example: SEC520). On One method of monitoring potential penetration is to look for abnormally large files. Issue use the command:<br><b><code><span style="color:#3366CC;font-size:1.2em;">find -P / -size +100000k</span></code></b># Did you see any files that are that size?
# The next section will apply some of these tools we have discussed into a shell script and crontab entry to periodically monitor and contact the system administrator of potential disk space issues (before they become a serious problem).
