Linux Server Hacks Volume Two phần 4 ppsx

On some Gentoo Linux distributions, the X font server port is set by the XFS_PORT directive in the /etc/conf.d/xfs configuration file. If you are using Gentoo and your font server starts but you can't contact it, check this file to make sure the font server is actually following the directives that you specified in its configuration file. Next, determine the appropriate limits for the number of clients that can connect to the font server and how the font server should behave when that limit is reached. This is done by a combination of the client-limit and clone-self settings in the xfs configuration file. The client-limit setting requires an integer value that determines the maximum number of clients that a specific font server will support before it refuses service to incoming requests. The clone-self setting requires a Boolean value and determines how the font server behaves when this limit is reached. If clone-self is on (true), the font server will start a new instance of itself when it reaches the maximum number of clients specified. If clone-self is off (false), the font server will attempt to contact any other servers identified in the alternate-servers entry, in order, until one can be contacted successfully. In environments with multiple centralized font servers that service large numbers of desktops, I'd suggest always having clone-self set to false, and starting out with a client-limit of 100. Once you see how well this performs, you can raise or lower this limit to best balance response time from the font server (affected by both system load and network bandwidth) with reasonable utilization of all of your font servers. As the final step in creating your X font server's configuration file, you'll need to add each directory that contains X fonts to the comma-separated value for the catalogue statement. The next section explains how to copy font files from remote systems to the X font server system and create appropriate entries for them in the font server configuration file. 3.5.3. Copying Fonts to a Font Server The next step in configuring your font server is to actually populate it with all of the fonts that you want it to deliver to your X Window System clients. The easiest way to do this is to examine the X Window System configuration files on each of your types of systems to see where they are currently getting fonts. This is specified in one or more FontPath statements in the Files section of the X Window System configuration file, which is either /etc/X11/xorg.conf (for X Window servers from X.org) or /etc/X11/XF86Config-4 or /etc/X11/XF86Config (for X Window servers from XFree86.org). If the Files section contains a single, uncommented statement such as the following, that system is using itself as a local font server: FontPath "unix/:7100" For each FontPath entry that points to an actual directory on the system you're examining, first check if the same directory (with the same contents) exists on the system where you'll be running your enterprise-wide X font server. If not, you'll need to copy the contents of that directory to the X font server system, creating the directory if necessary. Once any necessary directories have been cloned to the X font server system, make sure that those same directories are being identified in the catalogue statement in the X font server's configuration file. For example, the following are some sample statements from an X font server configuration file that refers to a local font directory: FontPath "/usr/X11R6/lib/X11/fonts/misc:unscaled" FontPath "/usr/X11R6/lib/X11/fonts/local" FontPath "/usr/X11R6/lib/X11/fonts/75dpi:unscaled" FontPath "/usr/X11R6/lib/X11/fonts/misc/sgi:unscaled" 122 122 After copying font directories to the machine that will be running the X font server, you will then have to update the X font server's configuration file, /etc/ X11/fs/config, to have equivalent statements. Each FontPath statement in the X server's configuration file translates into one of the comma-separated values associated with the catalogue keyword in the X font server's configuration file. Thus, an equivalent statement to the previous example would be the following: catalogue = /usr/X11R6/lib/X11/fonts/misc:unscaled, /usr/X11R6/lib/X11/fonts/75dpi:unscaled, /usr/X11R6/lib/X11/fonts/100dpi:unscaled, /usr/X11R6/lib/X11/fonts/misc/sgi:unscaled The last entry in the catalogue statement must not be followed by a comma. If you copy fonts into an existing font directory on the machine that will be running the X font server, you should su to root or use the sudo command to re-run the mkfontdir command so that all the fonts in that directory can be identified and delivered by the X font server. 3.5.4. Starting or Restarting the X Font Server Almost there! Before restarting the X font server to pick up the new settings and start offering fonts to any X clients that happen by, check the xfs startup script located in /etc/init.d/xfs to make sure that it doesn't explicitly specify a different port than the one on which your font server expects to listen. For example, suppose that your startup script contained a statement like the following: daemon check xfs xfs -port -1 -daemon -droppriv -user xfs You would want to modify this statement to the following: daemon check xfs xfs -port 7100 -daemon -droppriv -user xfs Some startup scripts use a variable to hold the port number. If this is the case in your font server startup scripts, make sure that the variable identifies port 7100 as the port on which to run the server. You're now officially ready to go! To restart (or start) your X font server, simply execute the following command: # /etc/init.d/xfs restart If the font server isn't already running, the stop portion of the restart will fail, but the start portion will start your X font server with all your new options. 123 123 Make sure you add the X font server startup fairly early on in your various runlevels, especially if you start your machine in graphical mode. If the X font server isn't available when you try to start the X Window System itself, and no local fonts are available, X will fail to start. 3.5.5. Updating Desktop Systems to Use an X Font Server While there's a bit of work involved in setting up your X font server and making sure it offers all the fonts your clients will need, switching a desktop system to use a remote X font server is easy. As mentioned previously, many modern desktop Linux distributions already use a local font server (i.e., a font server that is running on the same host as the X server) to deliver fonts. Switching these systems to use a remote X font server is extremely easy. The key to where your X server gets its fonts is the Files section of its configuration file. As stated previously, if the Files section contains a single, uncommented statement such as the following, that system is using itself as a local font server: FontPath "unix/:7100" To switch this system to using the remote font server, change this line to something like the following: FontPath "tcp/fontserver1.vonhagen.org:7100" You should then restart the X server on your desktop system to ensure that it can contact the X font server and retrieve the fonts that it needs. If the system cannot contact the font server, starting X will fail, and you should follow some of the tips in the troubleshooting section of this hack. Otherwise, you're done! Though I'm a fan of centralizing X resources such as fonts to make everyone's lives easier, I use a somewhat paranoid X server configuration file that provides some fallback in case a font server or the network goes down. For example, the FontPath entries in the xorg.conf files for machines on my home office network are the following: FontPath "tcp/fontserver1.vonhagen.org:7100" FontPath "tcp/fontserver2.vonhagen.org:7100" FontPath "/usr/X11R6/lib/X11/fonts/75dpi:unscaled" FontPath "/usr/X11R6/lib/X11/fonts/misc:unscaled" FontPath "/usr/X11R6/lib/X11/fonts/local" This tells my X servers to try two local font servers first and then fall back to a minimized collection of local fonts if the font servers don't work for some reason. The font servers are just CNAMEs in my DNS server, so I can easily move them to different hosts as my computing environment evolves. The fallback entries cover those rare cases when I just want to start a single machine. 3.5.6. Troubleshooting If an X server can't contact your font server and that is the only font resource and you haven't provided any local fallback fonts, the X server will not start and will terminate with a message about not being able to 124 124 contact the font server. Luckily, both Linux and the X Window System include some helpful commands to enable you to diagnose the problem. First, on the font server, make sure that the font server is actually running by using the ps command, as in the following example: $ ps -ef | grep xfs root 13841 31053 0 04:39 pts/13 00:00:00 xfs wvh 13848 31053 0 04:39 pts/13 00:00:00 grep -i xfs Next, check that you can contact it successfully by retrieving a list of the fonts that it provides. You can do this using the fslsfonts command, as in the following example: $ fslsfonts -server fontserver1 :7100 This should display a long list of available fonts. If it doesn't, make sure that the font server is actually listening on the correct port, using a command like the following: $ netstat -an | grep 7100 tcp 0 0 0.0.0.0:7100 0.0.0.0:* LISTEN tcp 0 0 :::7100 :::* LISTEN unix 2 [ ACC ] STREAM LISTENING 862009 /tmp/.font-unix/ If you don't see this information and you can't contact the X font server using fslsfonts, make sure that you commented out the no-listen = tcp entry in your font server's configuration file. If you see messages like the following when you start your X font server, some of the directories specified in its configuration file either don't exist or don't contain valid fonts: xfs notice: ignoring font path element /usr/X11R6/lib/X11/fonts/Speedo (unreadable) xfs notice: ignoring font path element /usr/X11R6/lib/X11/fonts/CID (unreadable) xfs notice: ignoring font path element /usr/X11R6/lib/X11/fonts/local (unreadable) These messages are nonfatal, but you should clean up your font server's configuration file so that no other sysadmin is confused about whether these directories were supposed to contain fonts that have somehow gotten "lost." Finally, double-check that you have the right font server settings in your X server's startup file. You can use the fallback approach suggested in the previous section to start the X font server using a small collection of local fonts until you resolve your connectivity problems. While you're working on them, you can use the fslsfonts and xset fp (set font path for the X Window System) commands to, respectively, test connectivity to the font server and add it to your current X session for testing purposes. The xset fp command enables you to add a font server to the list of font sources that X applications search (known as a font path), using a command like the following: $ xset +fp tcp /fontserver1 :7100 125 125 You may need to cause the X server to re-probe its font sources by using the xset fp rehash command. While testing, you can also remove elements from your X font path using a command like the following: $ xset -fp tcp /fontserver1 :7100 You can determine the current settings for your X font path (along with other settings) by executing the xset -q command, which provides a variety of information about your working X Window System environment. 3.5.7. Summary The X Window System is a great thing for Linux and Unix users, but the number of available (or required) fonts can quickly escalate, especially in internationalized (I18N) environments. Some X Window System applications, such as Wolfram Research's Mathematica, also take advantage of many custom fonts in order to display results as nicely as possible. (Wolfram's docs even identify a font server that they export over the Internet for this purpose.) Centralizing resources such as fonts that are used by many of the machines in your computing environment can save local disk space and, more importantly, provide a single location where you can easily install custom fonts that multiple users may require. Be careful, thoughcentral resources simplify administration, but they can also provide single points of failure unless you architect your installation correctly. The disk space required to install most fonts locally is no big deal (or expense) nowadays. However, centralizing custom fonts is always a good idea. Installing custom fonts locally isn't really a problem until you upgrade or replace the machine on which they live, at which point you may forget that the machine had custom fonts installed. Once bitten, twice shy! An X font server is easy preventative medicine for this sort of problem. 3.5.8. See Also man xset• man xfs• man fslsfonts• http://www.x.org• http://www.xfree86.org• Hack 24. Create a CUPS Print Server Let printers announce themselves and create a flexible, modern printing environment by setting up CUPS. Today's printers are typically high-quality laser or inkjet printers, often capable of color printing and near-photographic quality. The original Unix printing system, known as lpd (Line Printer Daemon) was designed to queue and print jobs that were intended for huge, text-only line printers. As more sophisticated 126 126 printers were developed that were capable of higher-quality printouts (such as the original x9700, Canon-CX, and Imagen-300 laser printers), the original lpd print system continued to be used, but it required that the jobs you were printing be preprocessed so that they contained the special commands the printer used internally to produce higher-quality printouts. This quickly became tedious, because it meant that users had to know which printers they wanted to print to and required use of the appropriate preformatting commands. Eventually, the lpd system was updated and a similar printing system known as lp was developed. lp encapsulated the knowledge about the formats required by specific printers, implementing the necessary preformatting commands into filters (also known as print drivers) that automatically formatted files as required by the target printers. The evolution of multiple printing systems for Unix systems was not without pitfalls: it led to incompatibilities between the different print systems, required recompilation of the filters for specific printers for multiple Unix systems (if you could get the source code at all), and so on. Eventually, a company known as Easy Software Products began developing a more generalized printing system for Unix, Linux, and other Unix-like systems, called the Common Unix Printing System (CUPS). The original version of CUPS used the standard networked LDP protocol, but it quickly switched to using a new standard, the Internet Printing Protocol (IPP), which non-Unix/Linux systems such as Windows can use to print to CUPS printers. Easy Software Products also had the foresight to make the CUPS source code freely available under the GPL so that it could be compiled for multiple operating systems and thus become a true, cross-system standard popularized by zillions of users and sysadmins. This strategy has workedtoday, CUPS is used by every major Linux distribution and most other Unix-like systems. Almost every Linux system provides its own administrative tool for print system and printer configuration: SUSE provides YaST; Red Hat and Fedora Core distributions use printconf-gui; and so on. Printer configuration would therefore still be a sysadmin nightmare if not for the fact that the CUPS print daemon provides a built-in administrative tool that is easily accessed through any web browser via port 631. This provides a standard interface for CUPS configuration (though you're still welcome to use your Linux distribution's administrative printer configuration tools, if you insist). This hack focuses on the standard CUPS interface and web-based configuration. 3.6.1. Defining a New Printer in CUPS To define a new printer on any Linux system using the CUPS administrative interface, you must first make sure that the CUPS daemon, cupsd, is running on your system. You can do this using the ps command, as shown in the following example: $ ps alxww | grep cupsd 5 4 6923 1 16 0 24540 1452 - Ss ? 0:00 /usr/sbin/cupsd 0 1000 13304 31053 17 0 536 112 - R+ pts/13 0:00 grep -i cupsd If it isn't shown in the process listing, you can start it as the root user or via sudo, as in the following example: # /etc/init.d/cups start You should see an OK message once the system starts the CUPS daemon. Next, open your favorite web browser and connect to the network address http://127.0.0.1:631. The odd port number comes from its roots as an IPP print server (the default port for IPP is 631). The screen shown in Figure 3-1 will display. 127 127 When you see this screen, click the Do Administration Tasks link. An authentication dialog will display, into which you enter the name and password of a user who is authorized to do printer configuration on your system. The users who can administer printers and the print subsystem differ across multiple Linux distributions. On SUSE Linux systems, you must add authorized users to the CUPS authentication file using the lppasswd command (for example, lppasswda wvh would add the user wvh and prompt you twice for a password for printer administration by that user). On Red Hat, Fedora Core, and many other Linux distributions, you can simply enter the root user's login and password. Figure 3-1. The web-based CUPS administrative interface Once you successfully enter an authorized user's name and password, the screen shown in Figure 3-2 will display. Figure 3-2. The main CUPS admin screen 128 128 Click Add Printer to display the screen shown in Figure 3-3, where you can begin configuring your printer. (You can also get to this screen by selecting the Printers item from any CUPS page header and clicking the Add Printer button, but I think of this as an administrative action and therefore usually get there from the Admin page.) This hack focuses on configuring a local (physically attached) printer. "Configure Linux Connections to Remote CUPS Printers" [Hack #25] provides information on configuring a remote printer is provided in. Figure 3-3. The initial printer definition screen Enter a memorable short name for the printer in the Name field (most commonly without spaces), enter a summary of the printer's location in the Location field, and enter a short description of the printer in the Description field. The latter two are simply text strings, but putting meaningful values in these fields will help you remember which printer is which if your print server supports multiple printers. Click Continue to proceed. The screen shown in Figure 3-4 will display. Figure 3-4. Selecting how your printer is attached 129 129 Select the device to which your printer is attached from the drop-down list shown in Figure 3-4. As you can see, some Linux distributions auto-identify the printers attached to various ports when they perform hardware detection (this example screen was captured on a SUSE Linux system). After selecting the interface to which your printer is attached, click Continue. The screen shown in Figure 3-5 will display. Figure 3-5. Selecting your printer's manufacturer Select the manufacturer of your printer from the drop-down list in Figure 3-5. If the manufacturer of your printer isn't explicitly listed, your printer probably emulates a printer from some other manufacturer. (Printers that emulate various Hewlett-Packard printers are quite common. Any printer that supports PCLHP's Printer Control Languagecan emulate some sort of HP printer.) You'll note that many print drivers provide two printing options: gimp-print and foomatic. gimp-print is a print plug-in for the GNU Image Manipulation Program (GIMP) graphics package that includes many custom print drivers, while foomatic is a database-driven interface to another set of print drivers. I generally select whichever is marked as Recommended. If neither is recommended, it's usually best to start with gimp-print drivers, because gimp-print can also access foomatic drivers, but foomatic can't access the gimp-print drivers. Most Linux distributions preinstall these packages when you install CUPS, but you may have to install them separately on distributions whose goal is minimizing disk usage. Click Continue to proceed. A screen like the one shown in Figure 3-6 will display, listing all of the printers that are available from the selected manufacturer. Figure 3-6. Selecting a specific print driver 130 130 Select your printer (or an equivalent) from this list. It's important to select your printer exactly if possible, to best take advantage of the printer's capabilities. Click Continue to proceed. You'll see a summary screen telling you that the printer has been set up, which includes creating the right print queues and configuration entries that are used internally by CUPS. 3.6.2. Testing CUPS Printing Once you've set up a new printer, the first thing you'll want to do is test printing to it, not just to ensure that it is correctly configured in terms of ports and drivers, but also to check the default quality level for the printer. To do this, click the Printers entry in the heading of any CUPS administrative web page. A screen like the one shown in Figure 3-7 will display. Click the Print Test Page button. You should see your printer's activity light come on, and the printer should begin to print a CUPS test page. If the activity light doesn't come on, click the Jobs entry in the web page to display a page showing the status of the test print job. If this page shows that the job has completed, your printer is not configured correctly. The most common problems are that the printer isn't connected to the port that you selected in Figure 3-4, or that you've selected the wrong print driver. You can review and modify your current settings by clicking the Modify Printer button on the Printers page, which walks you through the steps described in the previous section using your current settings as defaults. Figure 3-7. Summary information about your printer 131 131 [...]... (SAMS) • "Create a CUPS Print Server" [Hack # 24] Chapter 4 Cool Sysadmin Tools and Tips Section 4. 1 Hacks 2 945 : Introduction Hack 29 Execute Commands Simultaneously on Multiple Servers Hack 30 Collaborate Safely with a Secured Wiki 147 148 Hack 31 Edit Your GRUB Configuration with grubby Hack 32 Give Your Tab Key a Workout Hack 33 Keep Processes Running After a Shell Exits Hack 34 Disconnect Your Console... [05/Sep/2005:17:55 :49 - 040 0] get_job_attrs: job #0 doesn't exist! E [05/Sep/2005:17:55 :49 - 040 0] print_job: Unsupported format 'application/ octet-stream'! I [05/Sep/2005:17:55 :49 - 040 0] Hint: Do you have the raw file printing rules enabled? These messages should help you identify the problem and suggest a fix 3.8 .4 See Also • http://www.cups.org/documentation.php • "Create a CUPS Print Server" [Hack # 24] • "Share... Install Linux Simply by Booting Hack 37 Turn Your Laptop into a Makeshift Console Hack 38 Usable Documentation for the Inherently Lazy Hack 39 Exploit the Power of Vim Hack 40 Move Your PHP Web Scripting Skills to the Command Line Hack 41 Enable Quick telnet/SSH Connections from the Desktop Hack 42 Speed Up Compiles Hack 43 Avoid Common Junior Mistakes Hack 44 Get Linux Past the Gatekeeper Hack 45 Prioritize... visible in the Printer Setup Utility Magic! 143 144 3.9 .4 Troubleshooting Mac OS X Printing to CUPS Servers The most common cause of being unable to print to a CUPS print server is that the printer is not configured to accept print jobs from your host's IP address [Hack # 24] If you're sure that this is not the problem, check the CUPS logfiles CUPS print servers maintain three logfiles that can provide... standard Linux passwords, but I find it most useful to require a separate password for printer access Using standard Linux passwords causes the print server to invoke the PAM modules for CUPS (defined in /etc/pam.d/cups), which often differ from Linux distribution to Linux distribution (PAMs were discussed in "Customize Authentication with PAMs" [Hack #4] ) Also, since most people using Linux systems have Linux. .. install a server farm, or just hacking around with new kernel builds on your web server, you can leave your scripting skills on the back burner by making use of grubby, a simple command-line tool that will edit your kernel definitions for you 153 1 54 Here's an example of a very simple kernel definition from a grub.conf file on a Red Hat Enterprise Linux server: title Red Hat Enterprise Linux AS (2 .4. 21-32.0.1.EL)... existing Linux/ Unix knowledge to working with Mac OS X Integrating Mac OS X printing with a CUPS server running on a remote Linux system is one of the best examples of this, because Mac OS X actually uses CUPS 140 141 as the core of its printing subsystem This hack explains how to use the familiar CUPS web interface to quickly and easily set up your Mac OS X systems to print to centralized CUPS print servers... files and are trying to print to a CUPS printer from Windows, you may see messages like the following: E [05/Sep/2005:17:55 :49 - 040 0] get_job_attrs: job #0 doesn't exist! E [05/Sep/2005:17:55 :49 - 040 0] print_job: Unsupported format 'application/ octet-stream'! I [05/Sep/2005:17:55 :49 - 040 0] Hint: Do you have the raw file printing rules enabled? It doesn't get much more helpful than this in terms of identifying... and are trying to print to a CUPS printer from Mac OS X, you may see messages like the following: E [05/Sep/2005:17:55 :49 - 040 0] get_job_attrs: job #0 doesn't exist! E [05/Sep/2005:17:55 :49 - 040 0] print_job: Unsupported format 'application/ octet-stream'! I [05/Sep/2005:17:55 :49 - 040 0] Hint: Do you have the raw file printing rules enabled? Talk about useful error messages! Double-check the changes... that with your favorite text editor 144 145 (which should be emacs) and a few minutes of your spare time You will have to restart the CUPS server after making any changes to the CUPS configuration file, as discussed in this (or any other) hack The startup script for your CUPS server is called cups and is typically located in /etc/init.d To restart the CUPS print server after saving your changes to its . [05/Sep/2005:17:55 :49 - 040 0] get_job_attrs: job #0 doesn't exist! E [05/Sep/2005:17:55 :49 - 040 0] print_job: Unsupported format 'application/ octet-stream'! I [05/Sep/2005:17:55 :49 - 040 0]. [05/Sep/2005:17:55 :49 - 040 0] get_job_attrs: job #0 doesn't exist! E [05/Sep/2005:17:55 :49 - 040 0] print_job: Unsupported format 'application/ octet-stream'! I [05/Sep/2005:17:55 :49 - 040 0]. being able to 1 24 1 24 contact the font server. Luckily, both Linux and the X Window System include some helpful commands to enable you to diagnose the problem. First, on the font server, make sure