More Scripting & Chapter 11 Software and Configuration Management

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)

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

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

Where to find RPMs? Below is the list of rpm sites, where you can find and download all RPM packages. http://rpmfind.net http://www.redhat.com http://freshrpms.net/ http://rpm.pbone.net/

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-*

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

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)

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

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.

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

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

2. Removing a Package with YUM

3. Updating a Package using YUM

4. List a Package using YUM

5. Search for a Package using YUM

6. Get Information of a Package using YUM

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

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 3.5.2 package, just execute the command. # yum --enablerepo=epel install

YUM Repos

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.