1. More Scripting & Chapter 11
Software and Configuration
Management

2. Package Management
Packing system make software installation as atomic as possible.
If there is an error the package can removed or reapplied
Maintains dependencies for other software and libraries
2 common package management systems for Linux are RPM (red hat package manager) and deb (Debian for Ubuntu)

3. Low Level Package Management
Both the RPM and .deb packaging systems now function as dual-layer soup-to-nuts configuration management tools. At the lowest level are the tools that install, uninstall, and query packages.
rpm options are --install, --upgrade, --erase, and --query

4. Low Level Package Management
For example, the command rpm --query --all lists the packages installed on the system.
# rpm --upgrade openssh-2.9p2-12.i386.rpm
error: failed dependencies:
openssh = 2.9p2-7 is needed by openssh-askpass-2.9p2-7
openssh = 2.9p2-7 is needed by openssh-askpass-gnome-2.9p2-7
openssh = 2.9p2-7 is needed by openssh-clients-2.9p2-7
openssh = 2.9p2-7 is needed by openssh-server-2.9p2-7

5. Where to find RPMs?
Below is the list of rpm sites, where you can find and download all RPM packages.

6. Low Level Package Management
# rpm --query --whatrequires openssh
openssh-askpass-2.9p2-7
openssh-askpass-gnome-2.9p2-7
openssh-clients-2.9p2-7
openssh-server-2.9p2-7
If you list multiple RPMs on the command line, rpm sorts them by dependency before installation.
# rpm --upgrade openssh-*

7. High Level Package Management
There are tools that know how to find packages on the Internet, analyze inter-package dependencies, and upgrade all the packages on a system.
yum, the Yellowdog Updater, Modified, works with the RPM system. The
Red Hat Network is specific to Red Hat Enterprise Linux and uses RPM.
The Advanced Package Tool (APT) originated in the .deb universe but works well with both .deb and RPM packages

8. Package Management
To simplify the task of locating and downloading packages
To automate the process of updating or upgrading systems
To facilitate the management of inter-package dependencies
Red Hat Network (commercial)
Yum (Red Hat, Fedora, CentOS)
Apt-get (debian / ubuntu)

9. Package Management Concepts
Release – the baseline, the target, snapshot of software package
A “component” is a subset of the software within a release with core software blessed by the distributor and extra software made available by the broader community.
An “architecture” represents a specific class of hardware.
Repositories

10. Package Repositories
Linux distributors maintain software repositories that work hand-in-hand with their chosen package management systems.
The default configuration for the package management system usually points to one or more well-known web or FTP servers that are under the distributor’s control.

11. YUM
YUM (Yellowdog Updater Modified)
1. Install a Package with YUM

12. 1. Install a Package with YUM yum -y install firefox (force)

13. 2. Removing a Package with YUM

14. 3. Updating a Package using YUM

15. 4. List a Package using YUM

16. 5. Search for a Package using YUM

17. 6. Get Information of a Package using YUM

18. 7. YUM Updating System Check for Available Updates using Yum
To find how many of installed packages on your system have updates available, to check use the following command.
# yum check-update
Update System using Yum
To keep your system up-to-date with all security and binary package updates, run the following command. It will install all latest patches and security updates to your system.
# yum update

19. 8. List all Enabled and Disabled Yum Repositories
The following command will display all enabled and disabled yum repositories on the system.
# yum repolist all
Install a Package from Specific Repository
To install a particular package from a specific enabled or disabled repository, you must use --enablerepo option in your yum command. For example to Install PhpMyAdmin package, just execute the command.
# yum --enablerepo=epel install

20. YUM Repos

21. At Home Exercises
1) Find all files in your home directory which has read permission only to group AND for each file change its group permissions to  r-x (read and execute) [try it by chaining commands together using -exec option for find]
2)How would you recognize a process that is hogging resources?  Assume that the process needs to be killed. What signal would you send, and why? What if you needed to guarantee that the process died?
3)What is the difference between hard links and symbolic (soft) links? When is it appropriate to use one or the other? Give an example of creating a hard link between two files.