RCHE Red Hat Certified Engineer Linux Study Guide[c] Exam (Rh302)

Here are some of the key points from the certification objectives in Chapter 4.

Adding, Deleting, and Modifying User Accounts

• After installation, your system may have only a single login account: root. For most installations, you'll want to create more accounts, even if only for everyday use.

• Accounts can be added by directly editing /etc/passwd or with the useradd command. The advantage of useradd is that it automatically adds the new home directory as well as configuration files from /etc/skel.

• Accounts can be added with the Red Hat User Manager utility. You can also use this utility or related commands such as chage and usermod to further configure the account with parameters such as a password lifetime or a time limit on the account.

• Discourage the use of shared accounts, where several people use a single account. Shared accounts are almost always unnecessary, and they are easily compromised.

• If you'll be using the Network File System (NFS), it can help to make user accounts with the same UID across systems. The Network Information System (NIS) can serve this purpose by establishing one database for all systems on your network.

The Basic User Environment

• Each user on your system has an environment when logged on to the system.

• The home directory for each login account is the initial directory in which users are placed when they first log on. They start with files from /etc/skel.

• Window manager configuration files are often stored in /etc/X11/windowmanager, where windowmanager is the name of the window manager. KDE window manager files are stored in each user's home directory.

Red Hat Filesystem Basics

• Linux filesystems can be loosely defined as regular and journaling filesystems. While there are other filesystems available, this describes the essential difference between the older ext2 and the current default ext3 filesystems.

Filesystem Management and the Automounter

• If you have the kernel source RPMs installed, you can review supported filesystems.

• A number of mount options are available for /etc/fstab. The defaults option sets up a partition as rw (read/write), suid (superuser ID files allowed), dev (device files read), exec (binaries can be run), auto (automatic mounting), nouser (mountable only by root), and async (data is read asynchronously).

Using the Red Hat Package Manager Command and Utility

• The RPM database tracks where each file in a package is located, its version, and much more.

• Verifying an installed package compares information about that package with information from the RPM database on your system or the original package.

• The install mode of RPM, as its name suggests, is used to install RPM packages on your system.

• The upgrade mode of RPM will replace the old version of the package with the new one.

• The rpm -e command (erase) removes a package from your system.

• Using the rpm command query mode (-q), you can determine which packages are installed on your system or what file belongs to a particular package.

• You can use the Red Hat Package Management utility to install a group of packages from sources such as your installation CD. With the right redhat-config-packages command, you can even point to a network source.

RPM Sources

• Source RPMs are, as the name indicates, contain the source code used to build architecture-specific packages.

• The spec file is stored in /usr/src/redhat/SPECS/packagename.spec. It controls the way a package is built, and what actions are performed when it is installed or removed from a system.

• Run rpmbuild -ba packagename spec to build your RPM and SRPM.

Network Configuration

• Key network configuration files are in the /etc/sysconfig directory: the network file, and the networking and network-scripts subdirectories.

• You can start the Network Configuration utility with the redhat-config-network command.

• To manage network settings on each interface, use dhclient (dhcp/bootp client management), ifup, and ifdown.

• The ifconfig command is used to configure and display network devices.

• Use ifup eth0 and ifdown eth0 to activate and deactivate the eth0 interface.

• The netstat command is used to display a plethora of network connectivity information.

• The arp command is used to view or modify the local hardware address database.

The Basic Boot Process

• Red Hat uses a boot process called System V init, which means that after the kernel is loaded, it starts a program called init, which then starts /etc/rc.sysinit.

• Study the /etc/rc.d hierarchy and the /etc/inittab and /etc/rc.d/rc.sysinit files. This is the key to understanding what's happening during the boot process.

• The chkconfig command gives you a simple way to maintain the /etc/rc.d directory structure. The redhat-config-services command provides a GUI tool for the same purpose.

Virtual Consoles

• Because Red Hat Enterprise Linux is a multiterminal operating system, it allows you to have more than one login session on the system console at a time using virtual consoles.

• By default, six virtual consoles are started when you boot Linux.

• You can switch between virtual consoles by pressing ALT-F1 to ALT-F6. By default, you start on the first virtual (ALT-F1) console screen.

• You can get to console mode from your X Window System session with CTRL-ALT-(F1 to F6). Return to the X Window System with ALT-F7.

Other Configuration Tools

• There are a number of non-network configuration files in the /etc/sysconfig directory.

• You can edit many of these files directly, or use GUI tools, which you can start with commands such as redhat-config-date, redhat-config-keyboard, redhat-config-mouse, and redhat-config-services.