Chapter 11 Managing Packages and Processes

What kind of graphical user interface is offered?

Synaptic and Software Center

What kind of Debian derivatives fo we have for package management systems?

Ubuntu and Mint are derivatives of Debian. At the heart of such distributions are software packages that are files ending in .deb

How do you go about adding Debian packages?

Well, these repositories contain more than 65,000 different packages of software. You will start by executing the $sudo apt-get update command to get a update list. Use $sudo apt-cache search <keyword> to locate the package yo wish to install. Once you find the correct package....use $sudo apt-get install <package> **Note--an internet connection is required for apt-cache to function.

cron

generated by crond daemon for jobs to be executed on a recurring basis.

dmesg

generated by the kernel during system boot up.

How do you know a update is available when in the GUI?

gpk-update-viewer will show a message in the GUI indicating updates are available.

secure

messages from processes that required authorization or authentication.

Xorg.0.log

messages from the X windows (GUI) server.

messages

messages from the kernel and other processes that don't belong elsewhere.

boot.log

messages generated as services are started during the startup of the system.

maillog

messages produced by the mail daemon for email messages sent or received.

What are some GUI based tools for RPM?

yumex and gpk-application

To update all packages

$yum update

To update individual software package

$yum update <package>

How do you list files of a particular package?

$dpkg -L <package>

How do you view a list of all the packages currently installed on the system?

$dpkg -l

What about querying a package?

$dpkg -s <package>

What are some tools for such systems?

$dpkg, apt-get, and aptitude

How do you view the processes of another user on the system?

$ps -u <username>

What command can you use to install, update, query, and remove packages?

$rpm **To add, update, or remove a package requires the command to be executed as the root user.

How do you list all packages currently installed on the system?

$rpm -qa

How do you determine if a particular file was put on the file system as the result of installing a package?

$rpm -qf /path/to/file

How do you query a package for information or its current state?

$rpm -qi <package>

How do you list the files that comprise a particular package?

$rpm -ql <package>

What can be used to automate the process of resolving dependency issues?

$yum and $up2date

To install a package...

$yum install <package>

How do you remove a package

$yum remove <package> this will remove packages and resolve any sort of dependency issues.

To search for a package...

$yum search <package>

Okay, now let's talk about RPM package management....

According to the Linux Standards Base, this is the standard package management system. The files end with .rpm for each software package and this system is what Red-Hat derived distributions like Red Hat, Centos, and Fedora, use to manage software.

Well, that was a lot of content but we finally made it.

END CH. 11 !!

What happens to old log files?

Log files are rotated, so, older log files are renamed and replaced with newer log files.

How are other processes started?

PID of 1 These are started through the /sbin/init. Earn one process starts another process, the process that performs the starting is called the parent process and the process that is started is called the child process.

What is the Linux kernel?

The kernel is loaded at boot time and stays loaded to manage every aspect of the running system. The kernel accepts commands from the user and manages the processes that carry out those commands by giving them access to devices like memory, disks, network interfaces, keyboards, mice, monitors, and more!

What are daemons?

These are system processes running in the background to perform logging. The log files are almost always placed in the /var/log directory.

What will the $lastb and $last commands do?

These commands will interpret file contents that are in binary and output plain text.

How can you view all processes on the system?

This can be done with $ps aux or $ps -ef commands. You can use the grep command to filter the output display lines that match a keyword, such as the process name.

Where can you find information regarding running processes?

This can be found in the /proc directory

Where can you find more information about hardware devices?

This can be found through the /dev directory and additional information about these devices can be found under the /sys directory.

What happens when maximum PID values are achieved?

This can happen when a system has been running for a long time. When it does occur, the system will "roll over" and begin assigning PID values that are available at the bottom of the range.

What does $pstree do?

This command allows you to "map" process into a family tree of parent and child couplings.

What does the $file command do?

This command will allow you to check the file content type before you view it to make sure the file is safe to view.

What will the $dmesg command do?

This command will display the kernel ring buffer, which will hold a large number of messages that are generated by the kernel. When running this command, make sure to filter the output with less or grep command. /var/log/dmesg will show display messages that are produced during system startup. /var/log/messages will show kernel messages that are produced as system is running.

What will the $free command do?

This command will provide a snapshot of the memory used at that moment. you can add the -s option to specify the amount of time to monitor. -m or -g options will display output in megabytes or gigabytes, respectively.

What is package management?

This is a system by which software can be installed, updated, queried, or removed from a file system. The two most popular systems are from Debian and Red Hat.

What is swap memory?

This is virtual memory--space on the hard disk that is used like physical memory when the amount of physical memory becomes low. When this happens, the system will automatically terminate processes when the amount of memory and swap available becomes very low.

How does one go about removing packages?

This should be done with caution!! Dependencies between packages mean if you remove a package, then all packages that need, or depend on that package, will be removed as well. $sudo apt-get remove <package> will remove files from software package expect the configuration files. $sudo apt-get --purge remove <package> will remove all software package files including the configuration files.

What does the $ls /proc command do?

This shows numbered directories for each running process on the system, where the name of the directory matches the PID (process ID) for the running process.

What does the $ps command do?

This will only show the current processes running in the current shell.

What does the $top command do?

This will regularly update the output of running processes--processes that are "CPU hogs" are listed first with the % of CPU time that each process is currently using. This command allows you the ability to monitor memory usage in real-time.

What are log files?

When output that is not displayed in the terminal window, it is sent to various "log" files. Typically called "log data" or "log messages". These are useful as they can help out with troubleshooting problems and determining whether or not unauthorized access has been attempted on the system.

How can you manually terminate processes?

With the $top or $kill commands.

Does the RPM package management system track dependencies between packages?

Yah!

Why would you want to leave configuration files behind?

You would do this in the event you plan to reinstall the software package at a later time.