Unsupported Printers
Unfortunately, some printers just won't work on Linux. There is a class of printers known as GDI printers, which tend to be cheap and frankly rather nasty printers they are designed to interact directly with the Windows graphics device interface, and they do not have an independent open printer control language. These printers are either unsupported or poorly supported in Linux. (This is, in a way, the printing equivalent of the Winmodem problem.) The best place to get good information about...
Using Webalizer
Another popular log analyzer is Webalizer. Webalizer was specifically written to produce an HTML page with graphing statistics for access to a web site. Figure 7-1 shows a Webalizer page for a relatively busy site. The webalizer package on openSUSE installs a binary executable usr bin webalizer that can be run manually, but is normally configured to be run as a scheduled task by cron. The configuration file is etc webalizer.conf. When webalizer is run, it creates a set of HTML pages from the...
Mware Virtual Machines
VMware is a commercial and proprietary virtualization product. VMware began as a desktop product for running Windows under Linux and vice versa, but now a number of products are offered, including expensive server versions (the VMware GSX and ESX servers) that allow server consolidation by letting you migrate a variety of servers running different operating systems onto a single physical server. You must pay for the Workstation product, but there are also two free download versions, VMware...
Office Formats
OpenOffice.org opens almost all Microsoft Word .doc, Excel .xls, and PowerPoint .ppt files, as well as its own and StarOffice native formats. As noted earlier in the chapter, to quickly extract the text from a Word file, antiword can be useful. The other office applications on Linux (AbiWord, Gnumeric, Koffice) are generally not as good as OpenOffice.org at opening alien files. You can try to educate your contacts to understand that if they want to send you a shopping list, it's not actually...
Compiling Source Code
To transform source code (C, C++, Fortran, and so on) to a machine architecture binary, you use a compiler. A compiler takes the source code and analyzes itfor syntactical and semantic errors (much like checking the spelling and grammar of text), tokenizing (splitting the source code into smaller, quantifiable chunks), and then producing a binary runtime. This runtime is linked to any libraries it relies upon to run. The internals of these operations are handled for the C programming language...
Global Directives
The global directives apply to the behavior of the Apache server as a whole they are pulled in by Include directives from a number of other files including etc apache2 uid.conf, etc apache2 server-tuning.conf,and etc apache2 listen.conf. 1 ' fYT The files under etc apache2 sysconfig.d are generated when the Apache - . ,t .-.5 . server starts from the information in etc sysconfig apache2 and should not be edited directly. Instead, changes should be made in etc sysconfig apache2 for the variables...
Vanilla kernel packages built for openSUSE are available at httpdownload opensuseorgrepositoriesKernel Vani 11
A Linux kernel has a version number such as 2.6.23.12 (the latest stable version of the kernel at the time of this writing). The convention is that the stable kernel series has a middle number that is even. Thus 2.0, 2.2, 2.4, and 2.6 are successive stable kernel series. The odd numbers represent the development series. For a long period while the 2.4 kernels were the stable series, 2.5 kernels were being issued in the development toward the current stable 2.6 kernel. The third and fourth...
The openSUSE Web Site
The openSUSE web site is www.opensuse.org, shown in Figure 5-6. This is the place to start for all information about the openSUSE project. You can download the entire openSUSE distribution here as ISO images. You can browse software that has been contributed via the openSUSE Build Service (which allows developers to build packages from source and make them available for different versions of Linux). You can read hundreds of articles on the openSUSE Wiki. You can join mailing lists and browse...
The exportfs Command
The exportfs command can be used to handle the exporting of directories directly from the command line. To export all directories listed in etc exports, use exportfs -a. If etc exports has changed, exportfs -r rereads etc exports and changes the state of the directories being exported accordingly. This is like using rcnfsserver reload. Configuring the NFS server with YaST Configuring the NFS server with YaST You can export a directory that is not mentioned in etc exports by using something like...
Shell Aliases
If you have long compound commands that you regularly type, a bash alias is a nice way of reducing the amount of typing and thinking you have to do. You can create aliases at the command line (for the current session only) or permanently in the file .alias. For example, if you want to be able to use the single letter command b as an alias for the command ssh user somemachine.mydomain.net, you can type the following user bible > alias b 'ssh user somemachine.mydomain.net' From now on, in the...
The RPM Header
Summary Logcheck system log analyzer Vendor Craig Rowland < crowland psionic.com> Packager Justin Davies < justin palmcoder.net> Logcheck is a software package that is designed to automatically run and check system log files for security violations and unusual activity. Logcheck utilizes a program called logtail that remembers the last position it read from in a log file and uses this position on subsequent runs to process new information. Some of the header options are...
Mail Facility Logging via syslog
The format of the syslog.conf file is relatively simple. The first field (on the left in Listing 7-2) specifies the name of the logging facility, followed by the logging level. The second field (on the right in the preceding listing) is the file or host to log this message to. j f - - p You will find that a lot of naming conventions in Linux, and Unix in general, are ' - > standardized in an unofficial way. The prefix.suffix notation is found in a few configuration files. In the syslog...
Creating and Managing the Samba Password File
The Samba server uses its own password file to authenticate users connecting from clients. On SUSE systems this is the file etc samba smbpasswd. Users that already exist on the system (in etc passwd, having their encrypted passwords in etc shadow) are not automatically added as Samba users. To add a samba user, you need to use the smbpasswd command, which adds or modifies a user in the file etc samba smbpasswd. To add a Samba user, run smbpasswd with the - a (add) option smbpasswd -a roger New...
Konqueror
It is both a web browser and a file manager, and much more. Konqueror is probably the most important achievement of the KDE team, and as a web browser it is very pleasant to use. Konqueror's HTML rendering engine has been incorporated by Apple into the Safari browser on Mac OS X. As a browser, Konqueror includes nice features such as tabbed browsing (where you can open various web sites within a single browser, each of which is created as a separately...
Printing in Linux The Role of Post Script
As we hinted previously, the essentials of printing in Linux have their origins in the way printing was handled in traditional Unix systems, which originally printed to line printers that were only capable of printing lines of text characters. The first printers with graphical capabilities used the PostScript language. As a result PostScript became a standard page description language. PostScript was introduced by Adobe Systems and dates back to 1982. It is both a page description language and...
Logging Dropped Packets
When your firewall has been configured to your liking, you will want to log any traffic that has not been explicitly sanctioned by you. To do this, you need a final rule before the packet hits the default policy for the chain that uses a target of LOG. The LOG target interprets the TCP IP packet and logs it via the syslog facility for you to monitor unauthorized traffic. Just logging raw, unauthorized traffic is quite difficult to manage, and thankfully the LOG target enables you to specify a...
Pluggable Authentication Modules
Before Pluggable Authentication Modules (PAM) came along, any application that needed to authenticate a user had to read the etc passwd and etc shadow files directly. This restricted how data about users was stored because the data always had to be in a text file. PAM provides authentication modules that can obtain user accounts from numerous sources an LDAP server, a SQL database, or a Windows Active directory, for example. PAM works by having a configuration file for each service that needs...
Taking Part in an IPX Network
The IPX protocol is closely associated with Novell NetWare. Traditionally NetWare setups used networking over the IPX protocol rather than TCP IP. Now, IPX is becoming rarer, but it is still in use. Novell NetWare has been extremely good at managing large pools of users (in the thousands), and this is why it is so popular with large organizations. A large proportion of universities have tens of thousands of user accounts that they must manage in an efficient manner. Linux is able to communicate...
Using pax
A nice alternative to tar and cpio is pax, which is capable of unpacking archives in both these formats. Its command syntax is also simpler to learn than either tar or cpio, both of which can give a new user headaches. It also offers a neater solution than tar to the problem of exactly copying an entire directory tree complete with permissions, timestamps, and symbolic links from one place to another. To create a pax archive file of the current directory, do the following user bible tmp> pax...
W
Wainwright, Peter, 409 Wall, Larry, 410 Wammu, for viewing phone records, 442-444 warnings, YaST's partitioning warning, 386 wbinfo command, 515 wc command, 285 web interface (CUPS), 531-534 enterprise architecture and, 670 setting up with Squid. See Squid web shortcuts (Konqueror), 210-211 web sites for downloading antiword package, 294 ATI drivers, 220-221 Cygwin X software, 207 desktop project, 214 diff and patch command manual, 293 GNU awk manual, 285 HOWTO collection on Samba, 515...
Output of route n
In this example, the IP address of the machine called bible is 192.168.131.70 255.255.255.0. As you can see from the routing table, there is a route to the 192.168.131.0 network through the eth0 device. The 0.0.0.0 IP address we talked about before can be seen in the code output, and this refers to the default router we are using if our routing table does not understand how to communicate with a machine we specify. In this case, the default route is 192.168.131.254. This is the IP address of a...
Persistent Naming of Network Interfaces
Historically, some versions of Linux have had the rather irritating problem that not all network interface names were stable. In the past, there were workarounds for this such as including a variable PERSISTENT_NAME in the configuration file corresponding to the specific device in the directory etc sysconfig network . In recent versions of SUSE, the persistent naming of Ethernet devices is handled in a much more elegant way through the udev kernel device management subsystem. If you find that...
Redirecting Traffic
What if you want to redirect traffic to a different port on the firewall This is very common when you are setting up a transparent HTTP proxy with something like Squid or another content proxy. A redirection rule does not redirect to an IP, only a port. This makes it a local rule to the firewall only. With this in mind, any redirect rules must have a matching INPUT rule that allows the traffic to be accepted on the redirected port. bible - iptables -t nat -A PREROUTING -p tcp --dport 80 -i eth0...
In the example here YaST has created the file etcnamedconf the file etcnamedd forwardersconf and everything under
The YaST DNS Server module is an example of how YaST has evolved to be capable of creating and maintaining relatively complex configurations. Regardless of whether you have a large corporate network or a small home network with an asymmetric digital subscriber line (ADSL), you will probably want to use a DNS server. In the case of a home network with multiple machines, you can make your life a lot easier by configuring a forwarding caching server to speed up your general Internet use, as well...
Sed
Sed is the stream editor that means that you can use it to edit a stream of text (from a file or from the output of a different program) according to rules that you define. In fact, these rules can be very complex and you can do very clever things with sed, but we suggest that for the more complex tasks these days, a modern scripting language (Python, Perl, or Ruby according to taste) may sometimes be a better option. For simple tasks (such as replacing all instances of a string in a file with...
Mount devhda5 mint o notail
Another option that you can specify when mounting a ReiserFS filesystem is to disable journaling. To turn off journaling, add the nolog parameter to the options that you supply to the mount command. At the time of this writing, the Reiser filesystem actually still executes its journaling algorithm internally when this option is specified but simply does not write this data to disk, so this option provides only a slight increase in performance at the potential detriment of reliability should...
Using the vim Initialization File
If you want to customize how vim works, you can add startup commands to the file .vimrc in your home directory. This file is used to set the profile for how vim works for you and is very useful. One popular feature of vim is its syntax highlighting. If you are editing C, or maybe Perl, vim can colorize your text so it is easier to read. Open the .vimrc file (it may not exist, which means you'll have to create it) and add the following to the file It is usually nice to be able to use the...
Copy and Paste in X
Windows users are used to using Ctrl+C and Ctrl+V for copying and pasting between applications. Almost all X applications follow the principle that selecting with the left mouse button copies and clicking with the middle button pastes. This is one reason why you should really make sure that you have a genuine three-button mouse when you run Linux. However, many applications, including KDE applications, also use the Ctrl+C Ctrl+V system. KDE has a clipboard application (klipper) that maintains a...
Setting Up SCPM
SUSE Configuration and Profile Manager (SCPM) is a profile manager for the SUSE system. Profiles allow you to define multiple configurations for the same system and switch between them. This is particularly useful for laptop users who, for example, need different network, proxy, and printer settings at home and at work. We will configure this same environment as a quick introduction to what can be achieved with SCPM. It is an extremely powerful component of the SUSE system that can profile any...
Strictrfc821 envelopes
If you want clients connecting to Postfix to have to strictly use RFC 821 envelope addresses (fully qualified and enclosed in angle brackets), then this option will deny any MAIL FROM RCPT TO non-RFC addresses. J1 rr SHSglf It may be a bad idea to set this because there are many mail servers that are broken W . 'CV-.w s in the sense that they are not fully compliant with the standards set in the RFCs, and so assume they can get away without the angle brackets, and so on.
Finding Files with find and locate
The find command searches the filesystem for files that match a specified pattern. The locate command provides a faster way to find files but depends on a database that it creates and refreshes at regular intervals. The locate command is fast and convenient, but the information it displays may not always be up-to-date this depends on whether its database is up-to-date. To use the locate command, you need to have the package findutils-locate installed. If the package is installed, the database...
Setting Up a Scanner
YaST's scanner module automatically detects and sets up a scanner if it can USB and SCSI scanners are supported, as well as Hewlett-Packard's all-in-one (scanner-printer-fax devices) USB devices and network scan stations. The ancient parallel port scanners are not supported and cannot be configured with this module. In most cases, if a USB or SCSI scanner is detected, YaST sets it up automatically. A few USB scanners require a firmware file to be installed. If this is required, YaST warns you...
Looking at the Configuration of the Running Kernel
Root bible proc zcat config.gz more Automatically generated make config don't edit CONFIG_X86 y CONFIG_MMU y CONFIG_UID16 y CONFIG_EXPERIMENTAL y CONFIG_CLEAN_COMPILE y When you get bored with reading this, type q to quit more. It is instructive to page through this file and look at the various options that refer to the hardware, filesystems, and so on that are to be supported by the kernel. The y at the end of lines means that the support for the relevant item is compiled into the kernel....
Configuring BIND for Caching and Forwarding
After installing the BIND DNS server using YaST, you need to edit its main configuration file etc named.conf. When you are configuring BIND to act as a central DNS server for your home or an organization, it is always a good idea to tap into your Internet service provider's DNS server as a resource to provide you with public DNS lookups. When you rely on another DNS server to go and find your DNS lookups, it is called a forwarder because it literally forwards your DNS lookups to another DNS...
Getting Started with Squid on SUSE
The SUSE installation media contain the Squid installation package first, you need to install this in the usual way using YaST. Squid is included in the YaST installation selection Network Server. For this discussion, we assume that you are setting up Squid on a machine on your network that can connect freely to the outside world. Start Squid with the command rcsquid start. The first time that Squid is started, it creates a hierarchy of cache directories under var cache squid . If you look in...
Setting Up a Samba Server Using YaST
YaST's Samba Server module can be found in the Network Services section of the YaST menus, or can be started using the command yast2 samba-server. 1. As with other Samba modules, the Samba Server module behaves differently according to whether YaST finds a previous configuration already in existence or not. If there is no previous configuration it runs as a wizard asking essential questions until it has the information to create a configuration. If a previous configuration already exists, it...
Completing Installation
Once you have finished with your hardware configuration, click Next. It has been a long road, but you have successfully installed SUSE at this point (see Figure 1-33). Pat yourself on the back if you are new to the world of Linux. Although installing Linux is much easier now than it used to be, you have begun a journey in which you will learn a great deal and join a worldwide community of Linux users whose help and insights (thanks to the Internet) are never far away. V welcome Syiitenttouljiia...
R
V iSM( ii* & . -W , In the early days of Linux, printing was difficult to set up and equally difficult to manage. The print system was known as LPD (line printer daemon). Just as with X configuration, in the early days, at least, grown men wept. I still have bitter memories from 1997 of trying to make sense of the Linux Printing HOWTO and then, when I thought I had cracked it, ending up with a huge stack of paper covered in apparent garbage (raw PostScript code). Fortunately, those days are...
Starting sendmail
Installing sendmail as described in the previous section also installs the sendmail startup script etc init.d sendmail and creates symbolic links that automatically start and stop sendmail at run levels 3 ( etc init.d rc3.d S14sendmail and etc init.d rc3.d K08sendmail, respectively) and 5 ( etc init.d rc5.d S14sendmail and etc init.d rc5.d K08sendmail, respectively). To start sendmail, execute the startup script manually, as in the following example To verify that sendmail is running and its...
IP Addresses
Every machine that takes part in a TCP IP network such as the Internet has an IP address. If you dial up and check your e-mail, you are given an IP address to distinguish you from other machines so that machines you communicate with know how to find you. An IP address is something called a dotted decimal number. We will take a private IP address (which we talk about later in the chapter) of 192.168.0.1 as an example. 192.168.0.1 is a dotted decimal number. The dots split up the number into...
Disk Space Usage
To see how much disk space is being taken up by files in the current directory, you can use the du command (think disk usage). du alone lists the current directory and each subdirectory together with the disk usage. du -h lists the output in human readable'' form (that is in kilobytes, megabytes or gigabytes). du -hs (s for summary) just tells you the total usage under the current directory. To see how much disk space is being used per filesystem, use the command df (think disk full). Often,...
Adding Information
When the LDAP server is up and running, you can populate the server with your information. Some tools available for LDAP help with the initial population of LDAP data, as well as migrating existing users on the system to the LDAP directory. Here, we will populate the server with information using an LDIF (LDAP Data Interchange Format) file. j r - - r PADL (the reverse of LDAP) provides some infrastructure tools that integrate with LDAP, providing a much easier environment for an administrator...
Configuring a Firewall with iptables
To configure a firewall on Linux, you need to get used to the iptables command, which is used to manipulate the kernel packet filtering settings from user space. (Refer to Chapter 6 for more information on TCP IP because an understanding of TCP IP is needed.) f - - r The terms ''user space'' and ''kernel space'' are used a lot in the Unix community. rr when something runs in kernel space, it is under the control and the constraints of the kernel. Something running in kernel space could be a...
Setting Up Desktop Effects
To get desktop effects to work, you need a suitable modern graphics card. Having installed SUSE, the easy way, particularly if you have done a GNOME install, is to run the Gnome Control Center and choose the icon Desktop Effects.'' This will attempt to install an appropriate driver for your card, reconfigure your graphics using sax2 to use that driver, and rewrite your display manager configuration ( etc sysconfig displaymanager), so that GDM or KDM starts the Xgl server rather than X. The...
All group passwd rpc
The network information that was entered in the final stage of the YaST configuration is stored in the file var yp securenets. To set up a NIS server entirely from the command line, use the following steps. 1. To set the NIS domain name, use the following ypdomainname disruptive.org.uk 2. To go through a set of configuration steps to define, run the program usr lib yp ypinit (note that this is not in the path by default, so you need to call it with its full path) 3. At this point, we have to...
Postfix maincf file Example
Queue_directory var spool postfix command_directory usr sbin daemon_directory usr lib postfix unknown_local_recipient_reject_code 550 debug_peer_level 2 debugger_command xxgdb daemon_directory process_name process_id & sleep 5 sendmail_path usr sbin sendmail newaliases_path usr bin newaliases mailq_path usr bin mailq setgid_group maildrop manpage_directory usr share man sample_directory usr share doc packages postfix samples readme_directory mail_spool_directory var mail canonical_maps hash...
Emacs Modes
This is where emacs really comes into its own. emacs provides different sets of key bindings and functions that are automatically associated with different types of files. The set of key bindings and functions for a particular type of file is known as a mode. For example, if you are editing HTML, emacs has a mode for HTML. If you are editing Perl code, emacs has a mode for Perl. In the same way, there are modes for all major programming languages, for shell scripts, for Makefiles, for almost...
Searching Files with grep
The grep (global regular expression print) command is a very useful tool for finding stuff in files. It can do much more than even the examples that follow this paragraph indicate. Beyond simply searching for text, it can search for regular expressions. It's a regular expression parser, and regular expressions are a subject for a book in themselves. When using or administering a system, you often need to look for lines in a file that contain a certain string. In the first example in the list...
The bochs PC Emulator
The bochs project goes back a long way. It is a free (licensed under the GNU LGPL) PC hardware emulator that provides a complete emulation of PC hardware in software. As is the case with QEMU and VMware (see later in the chapter), you can install an operating system into bochs. However, bochs does not offer virtualization of the underlying hardware to the guest. This means that it can be built and run on any Unix-like platform on any hardware architecture, but it also means that it is slow. For...
Runlevel Editor
Throughout the book, we have talked about enabling services at boot time. This is very important when dealing with Unix systems. A mail server would be useless if the server process itself did not start up at boot time. You would have to manually start the mail server every time the system booted, which is inefficient and time-consuming. The Runlevel Editor can be used to turn on and off system services at system boot in different runlevels. To load the Runlevel Editor, start YaST and select...
Virtual Machines Using QEMU
QEMU is an open source hardware emulator. It can emulate an x86 system on x86, but can also both emulate and run on some other architectures. In particular, it can emulate and run on the PowerPC architecture. QEMU packages are included in the SUSE distribution. QEMU is developed by the French genius Fabrice Bellard, and the latest version is always available from http fabrice .bellard.free.fr qemu . You can install most x86 operating systems in QEMU, including most versions of Windows and most...
Configuring sendmail
The primary configuration information for sendmail is stored in the file etc sendmail.cf. Additional configuration information is stored in the directory etc mail. The file etc sendmail.cf is a text file that contains configuration information consisting of name value pairs on separate lines of the file. Most systems that run sendmail create the file etc sendmail.cf from another file, send-mail.mc, which is often stored in the etc mail (Linux systems such as Red Hat) or usr lib mail cf...
Booting Concepts
The term booting comes from the saying Pull yourself up by your bootstraps, which is fundamentally what a machine must do. When power is applied to the processor, it carries out a self-check to make sure it is healthy and jumps to a predefined address in memory called the BIOS (basic input-output system) to load and initialize the system hardware. The BIOS is the piece of code that checks your system memory, initializes hardware, and checks to see if you have a bootable operating system. This...
The Initial Ramdisk
As the system boots, it needs drivers for the disk controllers and the filesystems on the hard disk otherwise, it will not be able to mount the disks. The necessary drivers may not be included in the kernel itself but loaded as drivers. This is not a problem on the running system but can create a chicken and egg'' situation at boot time. This problem is solved by loading the initrd into memory at boot time. (Typically the initrd loaded is whatever is pointed to by the symbolic link boot initrd,...
Printer Configuration
One of the biggest annoyances for Linux users in the past was the configuration of printers. In the Windows world, the addition of a printer is painless, but in Linux it seemed the process was always marred by problems with drivers and configuration options. The Common Unix Printing System (CUPS) print drivers have helped to provide a unified printer architecture for Unix in general, and with distributions such as SUSE providing powerful configuration front ends, printer configuration has...
Mount devsda1 mnt o nosuid
This command mounts the partition dev sda1 on the directory mint and ensures that no programs in that filesystem whose s bit is set will be able to take advantage of that fact to execute as a privileged (or specific other) user. Three final mount options that are generally useful are ro, rw, and remount. When mounting external or remote partitions, you may occasionally want to mount them read-only so that you cannot accidentally change their contents. You would do this by specifying the ro...
ToPDC or Not to PDC
A domain controller is a server that supplies authentication information for a Windows domain. If you want your Samba server to join an existing Windows domain, you probably do not want it to act as a primary domain controller because a primary domain controller will already exist (probably in the form of a Windows server). Starting a second primary domain controller on an existing Windows domain will certainly confuse any Windows systems that are already members of that domain and will...
Sendmail
As mentioned earlier in this chapter, sendmail is the most popular Mail Transfer Agent in use on Linux and Unix systems today, but is not used by default on SUSE systems because its configuration syntax is somewhat cryptic. However, if you are installing a SUSE system in an environment where sendmail is the default MTA, you'd be hard pressed to argue for using a different MTA on your SUSE box. The sendmail program was written by Eric Allman, whose delivermail program was the original ARPANET...
Figure 2821
Installing Windows 2003 as a Xen virtual machine windows Virtual Machine Console < roger-amd64> Configuration Files and Command-Line Tools Each virtual machine has a configuration file in etc xen vm. If you use file-based virtual machines (in other words, the virtual disk is a file), these are stored by default under var lib xen images . The following is an example of a configuration file name opensuse ostype opensuse extra disk vif 'mac 00 16 3e 10 ab 98', vfb 'type vnc,vncunused 1' This...
Apache logrotate Entry for accesslog
var log apache2 access_log compress dateext maxage 365 rotate 99 size +4096k notifempty missingok etc init.d apache2 reload endscript As you can see in Listing 7-8, a given logrotate entry is made up of multiple directives. Each of these directives gives logrotate some instruction as to how to behave toward the log files covered by that particular logrotate entry. Table 7-3 details each of the directives in this file and the actions they inspire. Compress Compress the file when it is rotated....
Adding or Editing Groups
To create or edit groups in your system, select Security and UsersOGroup Management or, from the command line, type yast2 groups. Similar to the User section, you are presented with a list of groups currently on the system (see Figure 9-24). You can select a group from the list and click Edit to change settings for that group, or click Add to create a new group. You can choose to filter the list to show all system groups or local groups only (that is, the groups made up of real human users)....
Dos2unixand unix2dos
DOS and Windows have a different convention for newline characters from Unix and Linux. In DOS, the newline character is a carriage return and a line feed, whereas in Unix it is just a linefeed. What this means is that there can be problems when dealing with files from one system on the other. The programs dos2unix and unix2dos will convert (by default in place) a file from one system of newlines to the other. This will silently overwrite the original file with its Unix-style line endings with...
SUSE Kernels and Vanilla Kernels
Traditionally, the kernels shipped by SUSE and other commercial Linux vendors have always differed from the official kernels (often known as vanilla kernels) that are available from www.kernel.org. Exactly how much difference there has been has varied with time. During the long period when the 2.4 kernel series was the stable kernel and extensive development was being done on the 2.5 series, a large number of 2.5 features were backported into SUSE's 2.4 kernels. The first release of the 2.6...
Strings ghex khexedit and antiword
If you are confronted with a file that the file command doesn't give very useful information about (perhaps it just reports data), it may be worth trying to view it with cat -v, with less, or with a text editor. If all you see is binary junk, you may still be able to find out something useful using the strings command, which searches inside a binary file for text strings and outputs them. The output may give some useful clues. The applications ghex or khexedit may also be useful. These are...
Configuring a DNS Server with YaST
YaST has a DNS Server module, which can be found in the Network Services section of the YaST menus, or can be called from the command line with the command yast2 dns-server. In the example in this section, you set up a simple DNS server using this module. As with YaST's DHCP server module (see Chapter 20), the behavior you see when running this module differs according to whether YaST finds a previously configured setup. If previous configuration files are not found, YaST runs as a wizard the...
Linux Enterprise Hardware The Big Players
We have already alluded to the fact that many of the big technology players are involved with Linux and with bringing Linux into the enterprise. This section surveys some of the major companies and technologies that have placed Linux so firmly in the enterprise space. We have always been big fans of ridiculously expensive hardware that runs Linux, and we think that is true for most ubergeeks (although we would never admit to being them ). The de facto hardware in the industry has to be...
Using chkconfig to Control Runlevels
The command chkconfig is a program that allows you to add and remove services from the runlevel directory of a specific runlevel. If this program did not exist, you could in theory create your own links to move from one runlevel to another for example, in the directory etc init.d rc3.d to etc init.d to make sure a process starts and stops in an order you dictate. The services that you can control with the chkconfig command are all of the scripts in the etc init.d directory. However, on a SUSE...
Xgl and Compiz
Around the time of the original release of SUSE 10.0 and SLED 10, there was considerable interest among Linux desktop circles about the introduction of exciting new features on the desktop. These were the use of Xgl as an alternative to X and a compositing window manager. Put in those terms, this does not sound very interesting, but what you can do with these features is novel and compelling. If you have the right hardware and drivers, you can have extraordinary visual effects on the desktop,...
Using squidGuard
The squidGuard filter can be used with Squid to prevent access to undesirable sites. It is an additional package that you may need to install from the installation media. The maintainers of squidGuard also offer a set of blacklists of pornographic and other undesirable sites that squidGuard reads into a database in memory when it runs. Any requests for URLs in the database will be blocked by Squid. In order to use squidGuard, you need an additional line in etc squid squid.conf redirect_program...
CSV Files
CSV (comma-separated values) is a common format for interchanging data, particularly as an export format from various commercial applications running on Windows. A CSV file consists of a set of lines of text. Each line is broken into fields by a field separator, which is usually the comma, and each field is usually surrounded by quotes. First Name,Second Name,Street Address,City The OpenOffice.org imports a CSV file into its spreadsheet how perfectly it will do this depends on the exact format...
NFS Security Considerations
As with SMB shares, you certainly should not make it available beyond the private network. The lists of allowed client IPs or hostnames in the exports file are no defense against someone who is able to alter a machine's IP address (which, with physical access, in practice means anyone). The problem referred to earlier about UIDs failing to match between server and client means that a user may have the wrong permissions on another user's files on the server,...
Network Address Translation
Network Address Translation (NAT) is a technology that allows you to ''hide'' your private IP network from the Internet. All traffic, whether it is to a web server or a mail server or so forth is seen at its destination as having come from your NAT box. The NAT box then does the reverse translation when the server you are communicating with needs to send you data back and will change the destination IP address to that of your private machine. The web mail server you are communicating with has...
Using the YaSt Dhcp Server Wizard
The first time that YaST's DHCP module is run, it runs as a wizard, asking you for the information it needs to create a valid configuration file. On subsequent occasions, YaST provides a slightly different interface to the same configuration information, which is discussed in the following section. To set up and configure a DHCP server for the first time using YaST, do the following 1. Start YaST's DHCP Server module. First you are asked to select the Ethernet interface or interfaces on which...
Zypper Options
As we noted previously, zypper's options are roughly compatible with those of rug. Here, we repeat the previous example, but using zypper Enabled Refresh Type Alias Name 1 Yes Yes rpm-md openSUSE-10.3-Updates openSUSE-10.3-Updates 2 Yes Yes yast2 openSUSE-10.3-DVD 10.3 openSUSE-10.3-DVD 10.3 root bible root zypper sa server ha-clustering SLES_10 LMB-ha * Adding repository 'LMB-ha' Repository 'LMB-ha' successfully added Enabled Yes Autorefresh Yes URL Now if we list the repositories, we see that...
Boot Loader Configuration
We talked in Chapter 4 about configuring the boot loader of the system using the boot loader configuration files directly. Here we will quickly use YaST to install a new boot option into the GRUB boot loader for the installation of a new Linux kernel. We hope that as you move through this chapter you will see there is more than one way to do things in Linux the easy, the interesting, and the downright hard way. We have concentrated on the easy and the interesting ways throughout the book and...
Adding the Zone to namedconf
To add the zone to the BIND server, you need to create a zone reference in named.conf zone palmcoder.net type master file This defines the zone palmcoder.net, which is the master for this zone and is located in the file var lib named palmicoder.net. When the zone is defined, you need to reload the DNS server's data with rcnamed reload Reloading name server BIND 9 done j r - - r When you define a node, you must specify the type of the zone itself. In this case, , we have defined the zone as a...
Configuration Using YaST
YaST's module for configuring Apache is contained in the package yast2-http-server. The module appears in the YaST menus in the Network Services section labeled HTTP Server. To call the module from the command line, type yast2 http-server. When the Apache packages are installed, a default set of configuration files are also installed. If YaST finds that these have not yet been changed in any way, the module runs in wizard mode to create a customized configuration. Clearly, the number of...
Setting Up User Access
The most common security issue for a web site is the need to password protect a directory or file. To do this, the first step is the creation of a password file. The password file needs to reside somewhere outside of the webspace. For example, if the web site's documents reside at srv www htdocs dir on the filesystem, then the password file needs to reside somewhere outside of that space, such as etc http-passwd. Creating the file is simple just use the htpasswd2 utility that comes with the...
Testing the POP3 Server with Telnet
+OK ready < 2282.1088970620 bible> +OK Password required for justin. pass password +OK justin has 1 visible message (0 hidden) in 544 octets. As you can see, the user justin has one unread mail that is 544 octets in length. You can pass other parameters to Qpopper to extend its functionality. For example, if you want to allow your users to enter their usernames in uppercase or mixed case format, you can add -c to the Qpopper command line in etc xinetd.d qpopper to enable this. Another...
Understanding the Display Environment Variable
As you'll see in the next few sections, the DISPLAY environment variable tells X Window system applications which device they should contact in order to display their output. In most cases, you won't have to set this variable because the default is always your local machine. However, in general, the DISPLAY environment variable is declared using a command such as the following The displayname specification uses the following form When specifying a DISPLAY, hostname specifies the machine on...
The files Macro for logcheck
doc CHANGES CREDITS README* systems linux README* attr(700,root,root) dir etc logcheck attr(600,root,root) config etc logcheck * attr(700,root,root) config etc cron.hourly logcheck attr(755,root,root) usr sbin logcheck.sh attr(755,root,root) usr sbin logtail The entries you want to note in this file are as follows defattr This macro sets the default file permissions for all files installed, unless explicitly stated for each file entry. doc An important files macro entry. It is used to specify...
HELO and EHLO
AHELO is the first part in a handshake (so called because that is how we civilly start a conversation). When an SMTP server receives a HELO from the client, it then responds with the capabilities of the SMTP server itself. As the SMTP grew, more features were added. For backward compatibility, the HELO command responded with the very standard response of what the SMTP server can do. If an SMTP client can understand extended SMTP commands, it can start the conversation with an EHLO (Extended...
The Squid
The main Squid log by default is at var log squid access.log. Exactly what is logged here depends on the options chosen in the configuration file. The options are explained as comments in the standard configuration file shipped with the SUSE package. In particular, if you set in etc squid squid.conf, the format of the log file will change to look more like Apache's access log. The difference can be seen in these two sample entries 1199366332.055 159 192.168.2.111 TCP_MISS 200 768 GET - DIRECT...
Output of chkconfig list with a Customized Runlevel
If you are customizing a runlevel for a specific purpose (again, for Apache in this example), you should choose the runlevel that is closest in principle to what you need to run just for Apache and then customize it to your situation. Because we do not need X Windows, but we do need a multiuser system with networking, we choose runlevel 3 as a default and then customize it down. 'You can also adjust runlevels with YaST's runlevel module (command yast2 runlevel). See Chapter 9 for more details.
DOS Emulation Using dosemu and dosbox
The online openSUSE repositories contain packages for two DOS emulators, dosemu and dosbox. They are similar, except that dosbox is intended as a platform for running DOS games. The dosemu package provided by openSUSE includes a version of FreeDOS, and free software DOS clone. However, it is possible to replace this with MS-DOS or another DOS variant if you want to. After the package is installed, all you need to do to run it is type either dosemu or xdosemu, and you will see a window with a...
Querying RPM Packages
To find out information about an RPM package, you must query the RPM database or the RPM package directly. You do this with the -q command-line option. If you are querying an installed RPM, you just need to use the -q parameter with the query type you want to use. If you need to query an RPM package file directly, you have to add the -p (package) directive. Querying RPMs is a very important part of administrating an RPM-based system because you may need to see what version of the software is...
Postfix Terminology and
The configuration options we just discussed represent only a small amount of what can be done with Postfix. We now talk about how this all works together and what it provides to you as a mail server administrator. Any parameter that starts with an SMTPD controls some part of an incoming SMTP-based connection. Similarly, any parameters starting with SMTP refer to outgoing (to other SMTP servers) connections. Configuring and Securing Your Relay Policy Postfix's relaying policy (allowing users to...
Also do this on the command line using rcSuSEfirewall2 start or rcSuSEfirewal stop
To select the network interfaces that will take part in the firewall configuration, click Interfaces. It is very important that you get this right otherwise, your configuration will be the wrong way 'round and will not work as you expect. In the sample network configuration previously in the chapter, you had eth0 as the internal network interface and ethl as the external public interface, so set that here as well (see Figure 24-5). I In this chapter, we have looked at firewalls on systems with...
Sound and Multimedia Formats
As far as sound is concerned, you can play .mp3, .ogg, and .wav files with a number of different applications, including RealPlayer, Audacious, amaroK, and Banshee. Some versions of openSUSE do not include mp3 support for all these applications by default, in which case you will need to add the mp3 codec to your favorite player manually. However, the RealPlayer application (command realplay) always has built-in mp3 support. As well as playing files from disk, the RealPlayer application plays...
Output of the ifconfig Command
Eth0 Link encap Ethernet HWaddr 00 03 FF 69 68 12 inet addr 192.168.131.70 Bcast 192.168.131.255 Mask 255.255.255.0 i net6 addr fe80 203 ffff fe69 6812 64 Scope Link UP BROADCAST NOTRAILERS RUNNING MULTICAST MTU 1500 Metric 1 RX packets 30256 errors 0 dropped 0 overruns 0 frame 0 TX packets 35690 errors 0 dropped 0 overruns 0 carrier 0 collisions 0 txqueuelen 1000 RX bytes 4048565 (3.8 Mb) TX bytes 34473633 (32.8 Mb) Interrupt 11 Base address 0x1080 lo Link encap Local Loopback UP LOOPBACK...
Diskless X Terminals
To act just as a display for programs that are running elsewhere does not require a great deal of physical resources the idea of using legacy hardware just to do this is an interesting one. We won't discuss this in any detail, but interest is growing in a thin-client approach to desktop computing using Linux. In a true thin-client situation, the client machine uses network booting to get its kernel, mounts its directory tree entirely across the network from a server by the Network File System...
Creating a Shared Mailbox
If you want to create a mailbox that is shared between certain users, use the cm command to create the mailbox and also set the access control list (ACL) for users on the mailbox. For example, if you have three users, justin, roger, and aimee, on the system, and you want them to be able to store and view messages in this folder, but not to be able to delete any, you can look up the access control codes in Table 17-1 and set the ACL on that folder using the sam command (set ACL on folder). I' SW...
Using a Windows Printer from Linux
To access a networked Windows printer from your Linux system using Samba, you must have created a printer definition entry for that printer using YaST. You can then print to it as you would to any other local or networked printer. To create a printer definition for a Windows printer after installing and configuring the Samba client software, follow these steps 1. Start YaST's Printer module (from the Hardware menu or using the command yast2 printer). This launches the dialog box shown in Figure...
Running Microsoft Windows Applications with Wine
According to the Wine web site at www.winehq.org Wine officially stands for wine is not an emulator. Wine is an open source implementation of the Windows API on top of X, OpenGL, and Unix. Think of Wine as a compatibility layer for running Windows programs. Wine does not require Microsoft Windows, as it is a completely free alternative implementation of the Windows API consisting of 100 percent non-Microsoft code. However Wine can optionally use native Windows DLLs if they are available. Wine...
User Authentication
A common requirement is to add user authentication so that only known users within the network can get web access via Squid. The simplest way to do this is to make use of whatever authentication methods are available on the machine where Squid is running, using PAM (Pluggable Authentication Modules). To do this, you need something like the following in etc squid squid.conf auth_param basic program usr sbin pam_auth This line says that you should use PAM for authentication Whatever...
Working with the Winbind Daemon
The Winbind daemon, winbindd, enables the Linux name switch service (nsswitch) to retrieve user and group information from a Windows primary domain controller (PDC). This provides a networked authentication mechanism similar to the Network Information System (NIS and NIS+) often used in computing environments that make heavy use of Sun's Network File System (NFS). The Winbind daemon enables Windows users to log in on a Linux machine using the Windows credentials provided by the PDC without...
The Cname Record
To create an alias of a host so that a lookup returns the same IP address, you use a CNAME record. It is an alias for a host name, and we have found it most commonly used to define the address www.hostname.tld when the web server is on the same host as the DNS server. When you have it composed, the zone file can be saved as a standard text file. You then need to add the zone to the named.conf file so that BIND can load and serve the zone to the network.
The CUPS Logs
CUPS logs its activity in three log files var log cups access_log, var log cups page_log, and var log cups error_log. The names are self-explanatory. The file access_log shows access to the CUPS server in a rather similar way to the Apache web server logs. It shows the requesting host name and the date for each access to the CUPS server. The file page_log shows the user and the job name, as well as the number of pages printed. Each page printed shows in the file as a serial number against the...
YaST Modules
The YaST system is split into nine main menus, each one providing a number of modules. i- i j If you want to load a YaST module without loading the main menu, you can enter 'j- .,.',' . yast2 modulename. For a list of modules available in your installed YaST environment, type yast2 -l. Most (but not all) of the module names are fairly self-explanatory. To load the software management module, type yast2 sw.single. Tables 9-1 through 9-9 comprise a list of YaST modules (as seen on an openSUSE...
Framebuffer Graphics
Any VESA2-compliant graphics adapter is capable of providing framebuffer graphics. Framebuffer graphics provide an abstraction layer for the graphics hardware in your computer system and provide an easy way for X to interact with and control your graphics hardware. If nothing else works, this is your best chance of getting graphics configured, but may not take advantage of any specialized features of your hardware. If you need to use framebuffer graphics, you can specify a graphical resolution...
