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13.7.2 System Updating from the GUI
In CentOS, you can perform a software update through the GUI. Along the top of the
Gnome desktop menu bar, if
software updates are available, you will see this symbol: .
Clicking on it will bring up the software update window as shown in Figure 13.10.
You can select which packages to update, update all of them or update none of them. In
this case, there are 90 updates available totaling 255.9 MB. These software updates not only
are of applications software but also operating system updates. As the window reminds
us, software updates “correct errors, eliminate security vulnerabilities, and provide new
features.” There is no reason not to do the updates unless you are running very low on disk
space. Even if you do not have time for the updates, you can launch them the next time you
have to leave your workstation.
Other forms of software maintenance will include troubleshooting the software, pro-
ducing user
documentation for the software, monitoring the system’s performance while
executing software, and removing software. We will explore some of your options for trou-
bleshooting software in the next chapter.
We have already examined various monitoring tools available in Linux, such as the
System Monitor, top, vmstat, iostat, and ps. Another handy command is
pmap
, which
reports on process memory usage. You can also explore many performance characteris-
tics of a running process in the /proc directory. Recall that every
running process has its
FIGURE 13.10
CentOS update window.
Software Installation and Maintenance
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own subdirectory, named after the PID. Within that subdirectory, you can find informa-
tion on the process’ CPU utilization (cpuinfo), memory usage (meminfo), file system usage
(mounts), and numerous other useful pieces of information.
In some cases, software will come with its own monitoring program(s). For instance, the
Apache web server can store performance information in log files or create reports that can
be made available from the command line or even via a web browser.
13.7.3 Software Documentation
Producing documentation for software may or may not be part of a system administrator’s
responsibility.
To write useful documentation, learning how to perform technical report
writing could be advantageous. The role of software documentation goes beyond merely
“how to” use the software. Information placed in such documentation might include any
or all of the following:
• How to install the software—although it is the system administrator’s role to install
the software, this information could potentially help users who will install their
own versions or future system administrators who might take over for the current
administrators.
• How to configure the software—the system administrator may be responsible for
configuring the software although this task may also fall on individual users. Or, the
individual users may want to reconfigure the software to better fit their needs or style.
• How to maintain the software—upgrading the software,
reporting bugs, creating or
updating accounts and so forth are all tasks that may fall on the administrator or
individual users.
• Training manuals—here, the administrator may write a step-by-step description
of how to use the features of the software, including some of the more basic fea-
tures for naïve users and more advanced features for those who will use the software
extensively.
• Errata—known problems in the software and solutions either derived locally or from
the software vendor.
And of course, if the system administrator learns the software to produce documen-
tation, this makes the administrator a go-to person for questions from the users of the
software.
13.7.4 Software Removal
The system administrator may at some point have to remove software. This occasion arises
when the software is obsolete (has been replaced by something better) or the intended
users of the software are no longer with the organization. It may
also be necessary if free
disk space is running low and a particular piece of software which is taking up too much
space is deemed not worth keeping.
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Removing software can be a very tricky proposition when that software consists of files
distributed across the file system. This is why the system administrator should always use
the proper removal tool rather than just deleting files. All of the package manager pro-
grams that we have discussed have facilities to remove software.
Using the Add/Remove Software GUI, by default, Install is selected. To remove soft-
ware, if the package has already been installed, once you select it you choose Remove. This
is located under the Selection menu. As expected, this will remove all of the files that cor-
respond to that particular package with the exception of files
that are dependencies from
other packages. You have an option of whether to retain or delete those files (if other files
depend on these files, they should be retained).
In rpm, the –e or --erase option will erase the specified package. The command must
include the package name, although in this case, it is merely the software title’s name, not
the name of the RPM file (i.e., there is no version or release number and you do not end the
name with .rpm). For yum, the option is remove as in
yum remove
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