Q-R

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quota

In Linux, a quota can limit users and or groups by number of inodes or disk space. Quotas can include hard and soft limits.

RAID (Redundant Array of Independent Disks)

RHEL 3 supports software RAID. You can use Anaconda to set up software RAID 0, 1, and 5 arrays. You can also set up RAID arrays using the fdisk and mkraid commands, as well as by configuring /etc/raidtab. Also known as Redundant Array of Inexpensive Disks.

RAID 0

A RAID 0 array requires two or more partitions or hard drives. Reads and writes are done in parallel, increasing performance, filling up all partitions or hard drives equally. RAID 0 includes no redundancy; if any partition or hard drive in the array fails, all data in the array is lost.

RAID 1

A RAID 1 array requires two or more partitions or hard drives. RAID 1 is also known as mirroring, because the same information is written to both partitions. If one disk is damaged, all data will still be intact and accessible from the other disk.

RAID 5

A RAID 5 array requires three or more partitions. Parity information is striped across all partitions. If one disk fails, the data can be rebuilt. It can be automatically written to a spare disk.

Red Hat Certified Engineer (RHCE)

Perhaps the most elite certification available for Linux systems administrators. Designed to qualify Linux administrators with significant experience in configuring Linux LANs with Red Hat Enterprise Linux 3.

Red Hat Certified Technician (RHCT)

Another elite certification for newer Linux administrators. Designed to qualify Linux administrators with significant experience in configuring Linux workstations with RHEL 3. RHCEs must also meet all RHCT requirements.

Red Hat Hardware Compatibility List

The Red Hat Hardware Compatibility List (HCL) specifies all hardware that has been tested on systems running the various Red Hat operating systems. Red Hat provides installation support for any hardware that is listed as 'support ' on their HCL.

Red Hat Package Manager (RPM)

The Red Hat Package Manager system sets up software in discrete packages. The associated rpm command allows you to add, remove, and upgrade packages.

redhat-config-*

Red Hat has created a series of GUI configuration tools to help configure a number of different systems and services. You can start them with a number of different commands that start with redhat-config-*. While it's usually faster to directly configure a configuration file, not every experienced administrator knows every detail of every major configuration file. I've summarized the tools described in this book in Table G-1.

Table G-1: Red Hat Configuration Tools

Command	Description
redhat-config-authentication	Supports client computers on NIS, LDAP, and Samba password databases. Also known as the Authentication Configuration tool.
redhat-config-bind	Configures a DNS server. Also known as the Domain Name Service configuration tool.
redhat-config-date	Sets the clock, and supports synchronization with a remote time server. Can also be started with redhat-config-time. Also known as the Date/Time Properties configuration tool.
redhat-config-httpd	Allows you to configure an Apache Web server. Also known as the HTTP configuration tool.
redhat-config-kickstart	Configures a file to automatically install RHEL 3. Also known as the Kickstart Configurator.
redhat-config-mouse	Lets you select a mouse or pointing device.
redhat-config-network	Starts the Network Configuration tool, which can help you configure the network interfaces on your system.
redhat-config-nfs	Allows you to configure exported NFS directories with a wide variety of permissions. Also known as the NFS Server Configuration tool.
redhat-config-packages	Opens the Red Hat Package Management tool, which allows you to manage the software on your system by RPM package or package group.
redhat-config-printer	Starts the Red Hat Printer Configuration tool, which can configure local printers as a server, or connections to remote printers.
redhat-config-proc	Allows you to configure kernel parameters in the /proc directory.
redhat-config-rootpassword	Lets the root user change his or her password.
redhat-config-samba	Starts the Samba Server Configuration tool, which allows you to share directories over a Microsoft Windows-based network.
redhat-config-securitylevel	Opens the Security Level Configuration tool, which allows you to set up a firewall.
redhat-config-services	Starts the Service Configuration tool, which is effectively a front-end for the chkconfig command.
redhat-config-users	Allows you to configure users and groups with the Red Hat User Manager.
redhat-config-xfree86	Opens the Display settings tool, which allows you to configure the graphics card and display.

refresh rate

This is the rate at which the image you see on your screen is redrawn, in hertz (Hz).

reverse (inverse) zone

A DNS reverse (inverse) zone can be required by some servers, such as Apache and sendmail, to make sure an IP address points to a real computer. If the reverse zone hostname does not match the IP address, the server might not respond.

rndc

The rndc command is used to manage the operation of a DNS server; it's preferred to commands such as service named start.

root

This word has multiple meanings in Linux. The root user is the default administrative user. The root directory (/) is the top-level directory in Linux. The root user's home directory, /root, is a subdirectory of the root directory (/).

router

A computer that transfers messages between LANs. Computers that are connected to multiple networks often serve as routers.

runlevel

RHEL 3 includes six available runlevels, as defined in /etc/inittab. Key runlevels include 1, single-user mode; 3, text login; and 5, GUI login.

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