RHCT Vocab
Terms
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- ~
- The tilde (~) represents the home directory of the current user.
- Address Resolution Protocol (ARP)
- A protocol that maps an IP address to the hardware address on a network card.
- anacron
- The anacron service, while not included with RHEL 3, was formerly part of the RHCT prep course, and I believe an important tool for Linux administrators. It runs cron jobs that could not run while a server was powered down.
- apachectl
- The apachectl command is the preferred method to start and stop an Apache server.
- arp (Address Resolution Protocol) command
- The arp command is used view or modify the kernel’s ARP table. Using arp, you can detect problems such as duplicate addresses on the network. Alternatively, you can use arp to add the required entries from your LAN.
- at
- The at command is similar to cron, but it allows you to run a job on a onetime basis.
- BIND (Berkeley Internet Name Domain)
- BIND is the Unix/Linux software used to set up a Domain Name System (DNS) service. The associated daemon is named.
- /boot
- The directory with the main files required to boot Linux, including the Linux kernel and initial RAM disk. By default, /boot is mounted on a separate br />partition.
- BOOTP
- A TCP/IP protocol that sends IP address information from a remote DHCP server.
- caching-only name server
- A caching-only name server performs many of the functions of a DNS server. It stores the IP address associated with recent name searches, for use by other computers on your LAN.
- Apache Web server
- The Apache Web server provides both normal and secure Web services. Apache is controlled by the httpd daemon.
- authentication
- The way Linux checks the login rights of a user. Linux and Unix users are normally authenticated through use of a username and password, checked against /etc/passwd and related files.
- Automounter
- The Automounter can be configured to mount local and network directories on an as-needed basis. It’s configured in /etc/auto.master and /etc/auto.misc.
- chage
- The chage command manages the expiration date of a password.
- chains
- Chains are iptables (or ipchains) commands that are linked together. These are linked rules that are applied to each network packet that passes through a Linux firewall computer. iptables is the standard for RHEL 3.
- chgrp
- The chgrp command changes the group that owns a file.
- chkconfig
- The chkconfig command manages runlevel service information. It can activate or deactivate services. It can also customize services at specific runlevels.
- chmod
- The chmod command changes the permissions on a file.
- chown
- The chown command changes ownership on a file.
- CIFS (Common Internet File System)
-
CIFS is the Microsoft name for
advances in its networking software. It’s also covered by the latest version of Samba, 3.0, which is included with RHEL 3. - CNAME (canonical name)
-
The CNAME is a way to assign several different
names to a computer in a DNS database. For example, you can set up www as an alias for the computer with your Web server. CNAME records cannot be assigned to a mail server (MX) or a Start of Authority (SOA) record. - cron
- A service which runs jobs on a periodic basis. It’s configured in /etc/crontab; by default, it executes jobs in the /etc/cron.hourly, /etc/cron.daily, /etc/cron.weekly and /etc/cron.monthly directories.
- crontab
- Individual users can run the crontab command to configure jobs that are run periodically.
- CUPS (Common Unix Printing System)
- CUPS is the default print service for RHEL 3.
- usermod
- The usermod command modifies different settings in /etc/passwd, such as expiration date and additional groups.
- Very Secure FTP (vsFTP)
- The Very Secure FTP service is the default FTP server for RHEL 3.
- X Font Server
- The X Font Server, xfs, has to run before you can start theLinux GUI.
- X Display
- The X Display is a console and a virtual window. By default, there are six virtual consoles configured with Linux; the X Display is associated with virtual console number seven.
- X client
- An X client is an application that uses the X server services to display output.
- window manager
- The window manager is a special type of X client that<br />controls how other X clients appear on your display.
- volume group (VG)
- A collection of physical volumes (PV) in LVM.
- vi
- The vi editor is a basic Linux text editor. While other editors are more popular,vi may be the only editor you have available in the linux rescue environment.
- vgcreate
- Creates a volume group (VG) from two or more physical volumes (PV) for LVM.
- ypbind
- The NIS client service is ypbind.
- xinetd daemon
- The xinetd “super-server†daemon controls connections to servers in the /etc/xinetd.d directory such as the Kerberos Telnet server and POP3 e-mail.
- xhost
- The xhost command can be used to allow other hosts to access your X server. In other words, you can configure remote X clients to send their display to the local X server.
- XFree86
- The XFree86 server is the default X server for RHEL 3.
- X Window System
-
The GUI for Linux is also known as X Window. Unlike
other applications, the X Window System is a layered application. - X server
- The X server is the part of the X Window System that runs on your desktop. The X server draws images on your screen, takes input from your keyboard and mouse, and controls access to your display.
- user ID (UID)
- Every Linux user has a user ID, as defined in /etc/passwd.
- umask
- The umask command defines default permissions for newly created files.
- tmpwatch
- The tmpwatch command removes files that have not been accessed in a specified number of hours. The default daily tmpwatch script checks files in the /tmp and /var/tmp directories.
- TCP/IP (Transmission Control Protocol/Internet Protocol)
- TCP/IP is a suite of communications protocols for internetwork communication. It is primarily used as the communication system for the Internet.
- SRPM (source RPM)
- SRPMs include the source code required to build a binary RPM package. SRPMs are installed with the rpm -i command, which installs SRPM files within the /usr/src/redhat directory. You can then use the rpmbuild command to create a binary RPM. SUID The SUID bit sets common user
- superuser
- The superuser represents a regular user who has taken root user privileges. Closely associated with the su and sudo commands.
- swap space
- Linux uses swap space for less frequently used data that would otherwise be stored in RAM. It is normally configured in Linux in a swap partition.
- SUID
- The SUID bit sets common user ID permissions on a file or directory.
- Shadow Password Suite
-
The Shadow Password Suite creates an additional
layer of protection for Linux users and groups in the /etc/shadow and /etc/gshadow files. - showmount
- The showmount command lists the shared directories from an NFS server.
- single-user mode
- When you start RHEL 3 in single-user mode, you’re automatically logged in as the root user, without networking or most services. If your Linux system has boot problems, single-user mode may allow enough access to fix them.
- smbmount and smbumount
- The smbmount and smbumount commands,when properly configured, allow regular users to mount directories shared over a Microsoft Windows network through Samba.
- SMTP (Simple Mail Transfer Protocol)
- A TCP/IP protocol for sending mail. sendmail uses SMTP.
- soft limit
- Associated with user quotas. Specifies the maximum amount of space a user can have on a partition. Soft limits can be configured with grace periods.
- SGID
- The SGID bit sets common group ID permissions on a file or directory.
- server
- A computer that controls centralized resources such as files and printers. Servers can share these resources with client computers on a network.
- sendmail
- A standard e-mail server application. Most Internet e-mail uses sendmail.
- Samba
- The Linux and Unix implementation of the Server Message Block protocol and the Common Internet File System. Allows computers that run Linux and Unix to<br />communicate with computers running Microsoft Windows operating systems.
- 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.
- 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 (/).
- refresh rate
- This is the rate at which the image you see on your screen is redrawn, in hertz (Hz).
- 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-kickstart
- Configures a file to automatically install RHEL 3. Also known as the Kickstart Configurator.
- redhat-config-httpd
-
Allows you to configure an Apache Web server. Also
known as the HTTP configuration tool. - redhat-config-date
- Sets the clock, and supports synchronization with a remote time server. Can also be started with redhatconfig-time. Also known as the Date/Time Properties<br />configuration tool.
- redhat-config-bind
- Configures a DNS server. Also known as the Domain Name Service configuration tool.
- redhat-config-authentication
- Supports client computers on NIS, LDAP, and Samba password databases. Also known as the Authentication Configuration tool.
- redhat-config-*
- Red Hat has created a series of GUI configuration tools to help configure a number of different systems and services. They can be started with several different commands that begin with redhat-config-*.
- 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.
- 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. - 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.
- 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.
- 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.<br />If one disk is damaged, all data will still be intact and accessible from the other disk.
- RAID 0
- A RAID 0 array requires two or more partitions or hard drives. Reads and writes are done in parallel, increasing performance and 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 (Redundant Array of Independent Disks)
- RHEL 3 supports software RAID. You can use Anaconda to set up software RAID 0, 1, and 5 arrays.
- quota
- In Linux, a quota can limit users and/or groups by disk space or the number of inodes. Quotas can include hard and soft limits.
- pvcreate
- The pvcreate command allows you to configure PEs from a properly configured partition.
- /proc
- /proc is the Linux virtual filesystem. In this case, virtual means that it doesn’t occupy real disk space. /proc files are used to provide information on kernel configuration and device status.
- Primary Domain Controller (PDC)
- A PDC is the governing server on a Microsoft Windows NT 4–style network. You can configure RHEL 3 with Samba to function as a PDC.
- NIC (network interface card)
- A NIC connects your computer to a network. A NIC can be anything from a Gigabit Ethernet adapter to a telephone modem.
- physical volume (PV)
- An area of space for an LVM, which usually corresponds to a partition or a hard drive.
- physical extent (PE)
- A chunk of disk space created from a PV for LVM.
- PATH
- A shell variable that specifies the directories (and in what order) the shell automatically searches for input commands and files.
- PAM (Pluggable Authentication Module)
- PAM separates the authentication process from individual applications. It consists of a set of dynamically loadable library modules that configures how an application verifies its users before allowing access.
- NIS (Network Information System)
- NIS allows you to share one centrally managed authorization database for the Linux and Unix systems on your network.
- NFS (Network File System)
- NFS is a file-sharing protocol originally developed by Sun Microsystems; it is the networked filesystem most commonly used for networks of Linux and Unix computers.
- Network Time Protocol (NTP)
- The Network Time Protocol allows you to synchronize your computer with a central timeserver. You can do this on RHEL 3 with the Date/Time Configuration tool.
- netstat
- The netstat command can display connectivity information for your network cards. For example, the netstat -r command is used to display the routing tables as stored in your kernel.
- mount
- The mount command can specify mounted partitions, or attach local or network partitions to specified directories.
- mkfs
- The mkfs command can help you format a newly configured partition.
- mkbootdisk
- The mkbootdisk command can create a boot disk, customized for your system.
- MBR (Master Boot Record)
- The first sector of a bootable disk. Once the BIOS cycle is complete, it looks for a program on the MBR, which then looks at a boot loader configuration file such as grub.conf to see how to start an operating system.
- logrotate
- The logrotate command utility allows you to maintain log files. By default, RHEL 3 uses the cron daemon to rotate, compress, and remove various log files.
- lpc
-
You can use the lpc command to manage the queues associated with an
individual printer or a printer class. - lpq
- You can use the lpq command to view print jobs still in progress.
- lpr
- You can use the lpr command to send print requests.
- lprm
- You can use the lprm command to remove print jobs from the queue.
- lvcreate
-
The lvcreate command creates a logical volume (LV) from a specified
number of available PEs. - lvremove
-
The lvremove command is functionally opposite to the lvcreate
command.
MBR (Master Boot Record) The first sec - Logical Volume Management (LVM)
- Logical Volume Management (LVM) allows you to set up a filesystem on multiple partitions.
- logical volume (LV)
- A logical volume (LV) is composed of a group of LEs.
- logical extent (LE)
-
A logical extent (LE) is a chunk of disk space that
corresponds to a physical extent (PE). - locate
-
The locate command searches through a default database of files and
directories. - Lightweight Directory Access Protocol (LDAP)
- The Lightweight Directory Access Protocol allows you to keep authentication information on a central server on your network.
- lftp
- The lftp command starts a slightly more flexible FTP command line client.
- LDP (Linux Documentation Project)
-
The LDP is a global effort to produce
reliable documentation for all aspects of the Linux operating system. Its work is available
online at www.tldp.org. - Internet Printing Protocol (IPP)
-
The Internet Printing Protocol (IPP) is the
evolving standard for printers shared over networks. It’s being adapted by all major
operating systems; the Linux implementation is CUPS. - iptables
-
The iptables command is the basic command for firewalls and
masquerading. - KDE
-
A GUI for Linux and Unix computers. Also known as the K Desktop
Environment. - kernel
-
The kernel is the heart of any operating system. It loads device drivers.
You can recompile a Linux kernel for additional drivers, for faster loading, and to
minimize the required memory. - kernel module
-
Kernel modules are pluggable drivers that can be loaded and
unloaded into the kernel as needed. Some loaded kernel modules are shown with
the lsmod command. - GNOME (GNU Network Object Model Environment)
-
GNOME is the
default GUI desktop for Red Hat Enterprise Linux. - group ID
- Every Linux group has a group ID, as defined in /etc/group.
- GRUB (Grand Unified Bootloader)
- The default boot loader for RHEL 3.
- grub-install
-
The grub-install command makes your BIOS look for your GRUB
boot loader. - home directory
- The home directory is the login directory for Linux users. Normally, this is /home/user, where user is the user’s login name. It’s also represented by the tilde (~) in any Linux command.
- ifconfig
- The ifconfig command is used to configure and display network devices.
- init
-
The init process is the first Linux process called by the kernel. This process
starts other processes that compose a working Linux system, including the shell. - getty
-
A getty is a terminal program, which includes prompts for a login and
a password. Virtual console gettys are configured through the mingetty program
via /etc/inittab. - gateway
-
A route from a computer to another network. A default gateway
address is the IP address of a computer or router that connects a LAN with another
network such as the Internet. - FTP (File Transfer Protocol)
-
A TCP/IP protocol designed to optimize file
transfers between computers. - fsck
- The fsck command checks the filesystem on a Linux partition for consistency.
- firstboot
-
The process that starts when you’ve configured RHEL 3 during
installation to boot into the GUI (runlevel 5). - firewall
-
A hardware or software system that prevents unauthorized access over a
network. Normally used to protect a private LAN from attacks through the Internet. - fips
-
The First Interactive Partition Splitter, fips, allows you to split existing
VFAT partitions. - Fedora Linux
- The successor to the freely available version of Red Hat Linux.
- filesystem
-
Filesystem has multiple meanings in Linux. It refers to mounted directories; the root directory (/) filesystem is formatted on its own partition. It also
refers to file formats; Linux partitions are typically formatted to the ext3 filesystem. - find
- The find command searches for a desired file through a given directory and its subdirectories.
- Filesystem Hierarchy Standard
-
The official way to organize files in Unix and Linux directories. The top-level directory is known as the root directory (/);
users’ home directories are configured in /home. - fdisk
- A standard disk partition command utility that allows you to modify the physical and logical disk partition layout.
- edquota
- The edquota command edits the quota for a user or a group.
- emacs
-
The emacs editor is a popular text editor, which can be run from a text
console. - environment
- Each user’s environment specifies default settings such as login prompts, terminals, the PATH, mail directories, and more.
- /etc/fstab
- The /etc/fstab configuration file defines default mounted directories.
- /etc/inittab
-
The /etc/inittab configuration file sets the default runlevel and starts
key processes such as terminal gettys. - /etc/X11/prefdm
-
The /etc/X11/prefdm configuration file specifies the preferred
GUI display manager. - exportfs
- The exportfs command allows shared NFS directories to be shared with a network.
- e2label
- The e2label command associates a device with a filesystem directory.
- dumpe2fs
-
The dumpe2fs command provides a lot of information about the
format of a partition. - DNS (Domain Name System)
-
This service maintains a database of domain names such as www.redhat.com and IP addresses like 206.132.41.202. If the domain
name is not in the local database, DNS is normally configured to look to other, more authoritive DNS servers. The associated daemon is named. - dmesg
- The dmesg command lists the kernel ring buffer, the initial boot messages.
- display manager
-
A Linux display manager includes a dialog box for your
username and password. Three major display managers are used in RHEL 3: gdm
(GNOME), kdm (KDE), and xdm. - Disk Druid
- Anaconda’s hard disk management program. While the functionality is similar to fdisk, it is easier to use. However, Disk Druid is available only during the Linux installation process.
- DHCP (Dynamic Host Configuration Protocol)
-
DHCP clients lease IP
addresses for a fixed period of time from a DHCP server on a local network. The
BOOTP protocol allows DHCP clients to get IP address information from a remote
DHCP server. The DHCP server daemon is dhcpd; the DHCP client daemon is
dhclient. - /dev
-
The directory with device files, used to represent hardware and software
components. - client
- A client is a computer that accesses information or resources from a server.
-
cron A service which runs jobs on a periodic basis. It’s configured in /etc/crontab;
by default, it executes jobs in the /etc/cron.hourly, /etc/cron.daily, /etc/cron.weekly,
and /etc/cron.monthly directories. -
A service which runs jobs on a periodic basis. It’s configured in /etc/crontab;
by default, it executes jobs in the /etc/cron.hourly, /etc/cron.daily, /etc/cron.weekly,
and /etc/cron.monthly directories. - daemon
- A process such as the Web service (httpd) or X font server (xfs) that runs in the background and executes as required.