Linux Patch Management: Keeping Linux Systems Up To Date

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The Red Hat exams are given on computers built for an Intel-based 32-bit architecture.

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An Intel-architecture PC has three basic communications channels: IRQ ports, I/O addresses, and DMA channels.

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The latest version of Red Hat Enterprise Linux as certified should have at least 256MB of RAM.

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You can set up Linux on IDE, SCSI, USB, or IEEE 1394 hard drives. However, the BIOS of a PC can load Linux boot files only from the first two PATA, SATA, or SCSI drives.

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Linux is managed through a series of text configuration files.

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Understanding text editors is a critical skill. If you ever have to recover your system with a rescue CD, you may not have access to the GUI and will need to know how to use a console-based text editor such as vi.

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Linux directories are organized to the Filesystem Hierarchy Standard (FHS).

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In the FHS, devices such as mice and hard drives are grouped in the /dev directory. Some /dev files have logical names such as dvdwriter and are linked to the actual device files.

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FHS partitions can be managed and formatted with the fdisk, fsck, and mkfs commands.

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The Logical Volume Manager allows you to consolidate multiple partitions in one filesystem, on one directory.

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Once configured, Linux directories can be mounted on a partition through /etc/fstab or directly with the mount command.

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Linux administrators need to know how to use the command line interface.

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Basic commands allow you to navigate, find the files that you need, read file contents, create new files, and more.

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File filters allow you to search through the files themselves for specific citations or other file characteristics.

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Administrative commands allow you to manage Linux in a number of ways, including running processes and managing logged-in users.

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The default Red Hat Enterprise Linux print system is CUPS.

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You can configure printers by directly editing the files in the /etc/cups directory or by opening the Red Hat Printer Configuration tool with the system-config-printer command.

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Command lines are based on a shell.

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With the right permissions, you can set up shell programs in executable scripts.

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The way a shell works depends on the settings in its variables and parameters. Some variables and parameters are grouped in the inherited environment, which maintains settings from shell to shell.

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With stdin, stdout, and stderr, you can manage different data streams.

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Basic security within Linux is based on file permissions, users, groups, and umask.

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The SUID and SGID bits allow you to share owner-level permissions with different users and groups.

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Shadow passwords hide user authentication data. The Shadow Password Suite protects user and group passwords in files that should be accessible only to the root user.

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While it's normally best to log in as a regular user, it's faster to log in as the root user for the RHCE and RHCT exams.

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Standard files for new users are kept in /etc/skel.

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Daemons are processes that run in the background.

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Network service can be controlled through scripts in the /etc/init.d and /etc/ xinetd.d directories.

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The cron daemon helps you schedule different jobs, including backup and restore jobs, which should be done when network use is at a minimum.

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When you have problems, system log files, as organized by /etc/syslog.conf, provide important clues to the causes.

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Most of the work in TCP/IP networking is in configuring IP addresses.

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There are three different sets of private IPv4 addresses suitable for setting up TCP/IP on a LAN.

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IPv6 addresses include all available IPv4 addresses. If the first three bits of an IPv6 address are 001, that is a unicast address-in other words, one that is associated with a specific computer or other device.

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The first 48 bits of an IPv6 address are typically associated with a specific network.

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Tools such as ping, ping6, ifconfig, and netstat can help you diagnose problems on that LAN.

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Name resolution configuration files determine how your computer finds the right IP address.

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There are a number of standard network services, including NFS, sendmail, POP, IMAP, FTP, DNS, DHCP, Samba, Apache, and NIS.

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Each of these services, when installed, can be configured to start and stop through the scripts located in the /etc/rc.d/init.d or /etc/xinetd.d directories.

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Basic network security settings can depend on allowing or denying access to different computers by their IP addresses or by the desired TCP/IP port.

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Computers behind a firewall can be protected through Network Address Translation or various iptables commands.

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While GUI e-mail clients should be trivial, it's important to know how to configure a command line e-mail client.

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While GUI Web browsers should be trivial for serious Red Hat exam candidates, it can help to know a text-based browser such as elinks.

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While GUI FTP clients should be trivial for serious Red Hat exam candidates, it can help to understand a text-based FTP client such as lftp.

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There is no evidence that you need to know how to download the Red Hat installation CDs for the Red Hat exams.

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While the best option is to download the RHEL 5 CDs from the Red Hat Network, excellent options are available.

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You can use the rebuild distributions to prepare for the Red Hat exams. Their distributions are built on the same source code used by Red Hat for RHEL 5.