Running Linux in a Nutshell, Chapter 10: Installing the X Window System
(Reproduced with kind permision of O'Reilly & Associates: www.oreilly.com)
We come now to the X Window System - one of the most powerful and important software packages available for Linux. If you've ever used X on a Unix system before, you're in luck; running X under Linux is almost no different from Unix systems. And, if you've never had the occasion to use it before, never fear: salvation is at hand.
It's difficult to describe the X Window System in a nutshell. X is a complete windowing graphics interface for Unix systems. It provides a huge number of options to both the programmer and the user. For instance, there are at least half a dozen window managers available for X, each one offering a different interface for manipulating windows. By customizing the attributes of the window manager, you have complete control over how windows are placed on the screen, the colors and borders used to decorate them, and so forth.
X was originally developed by Project Athena at MIT and Digital Equipment Corporation. The current version of X is Version 11 revision 6 (X11R6), which was first released in April 1994. Since the release of Version 11, X has virtually taken over as the de facto standard for Unix graphical environments. It is now developed and distributed by The Open Group, an association that is composed of many large computer manufacturers.
Despite its commercial use, the X Window System remains distributable under a liberal license from the X Consortium. As such, a complete implementation of X is freely available for Linux systems. XFree86, an implementation of X, originally for i386 Unix systems, is the version most often used by Linux. Today, this version supports not only Intel-based systems, but also Alpha AXP, MicroSPARC, PowerPC, and other architectures. Further architectures will follow. XFree86 is based on X386-1.2, which was part of the official X11R5 sources, but is no longer maintained and is therefore outdated. The current versions now have only a very little part in common with their ancestors. Support for innumerable graphics boards and many other operating systems (including Linux) has been added - and XFree86 implements the latest version X11R6.3.
In this chapter, we will tell you how to install and configure the X Window System, and in the next chapter, we will explore how to use X.
Linux distributions automatically install X (if you ask them to). If you're lucky, you won't need this chapter at all. But a large percentage of users aren't lucky - the distribution doesn't recognize some graphics hardware, writes a file to the wrong location so the X server can't start up, or has some other problem. One of the big advantages of this book is that we take you down to the depths of X configuration so you can get it running no matter what your distribution does. You may not need to read this chapter, but if you do need it, you'll appreciate everything that's here.
X is based on a client-server model in which the X server is a program that runs on your system and handles all access to the graphics hardware. An X client is an applications program that communicates with the server, sending it requests such as "draw a line" or "pay attention to keyboard input." The X server takes care of servicing these requests by drawing a line on the display or sending user input (via the keyboard, mouse, or whatever) to the client application. Examples of X clients are xterm (which emulates a terminal within a window) or xman (an X-based manual-page reader).
It is important to note that X is a network-oriented graphics system. That is, X clients can run either locally (on the same system that the server is running) or remotely (on a system somewhere on a TCP/IP network). The X server listens to both local and remote network sockets for requests from clients. This feature is obviously quite powerful. If you have a connection to a TCP/IP network, you can log in to another system over the network and run an X application there, directing it to display on your local X server.
Further advantages of X are security (if the user so desires), the modular separation of functions, and the support for many different architectures. All this makes the X Window System technically superior by far to all other window systems.
The X Window System makes a distinction between application behavior and window management. Clients running under X are displayed within one or more windows on your screen. However, how windows are manipulated (placed on the display, resized, and so forth) and how they are decorated (the appearance of the window frames) is not controlled by the X server. Instead, it is handled by another X client called a window manager that runs concurrently with the other X clients. Your choice of window manager will decide to some extent how X as a whole looks and feels. Most window managers are utterly flexible and configurable; the user can select the look of the window decoration, the focus policy, the meaning of the mouse buttons when the mouse is on the background part of the screen rather than on an application window, and many other things by editing the configuration files of the window manager. More modern systems even let you configure those aspects over a graphical user interface.
In order to fully understand the concept of window managers, you need to know that the window manager does not affect the presentation of the window created by the client. The window manager is only in charge of painting the window decoration, that is, the frame and the buttons that let you close, move, and resize windows.
There can be only one window manager on any X server. Theoretically, it is even possible to completely do away with window managers, but then you would not be able to move windows around the screen; put a hidden window on top; or minimize, maximize, or resize windows unless the programs themselves provide this functionality.
As of XFree86 Version 22.214.171.124, released in January 1999, the video chipsets listed in this section are supported. The documentation included with your video adaptor should specify the chipset used. If you are in the market for a new video card, or are buying a new machine that comes with a video card, have the vendor find out exactly what the make, model, and chipset of the video card is. This may require the vendor to call technical support on your behalf; vendors usually will be happy to do this. Many PC hardware vendors will state that the video card is a "standard SVGA card" that "should work" on your system. Explain that your software (mention Linux and XFree86!) does not support all video chipsets and that you must have detailed information.
A good source for finding out whether your graphics board is supported and which X server it needs is https://www.xfree86.org/cardlist.html.
You can also determine your video card chipset by running the SuperProbe program included with the XFree86 distribution. This is covered in more detail later.
The following accelerated and nonaccelerated SVGA chipsets are supported:
Video cards using these chipsets are normally supported on all bus types, including the PCI and AGP.
All of these chipsets are supported in 256-color mode, some are supported in mono- and 16-color modes, and some are supported on higher color depths.
The monochrome server also supports generic VGA cards, using 64k of video memory in a single bank, the Hercules monochrome card, the Hyundai HGC1280, the Sigma LaserView, the Visa, and the Apollo monochrome cards.
The VGA16 server supports memory banking with the ET4000, Trident, ATI, NCR, OAK and Cirrus 6420 chipsets, allowing virtual display sizes up to about 1600x1200 (with 1 MB of video memory). The maximum display size for other chipsets and X servers varies, but you can get 1024x768 with most modern chipsets, often more (this also depends on the amount of video memory available and the color mode that you choose).
This list will undoubtedly expand as time passes. The release notes for the current version of XFree86 should contain the complete list of supported video chipsets. Please also always see the README file for your particular chipset.
Besides those chipsets, there is also support for the framebuffer device in the 2.2 kernel series via the FBDev server; this kernel has unaccelerated support for several chipsets for which there is not yet a dedicated server; it also supports acceleration on some hardware. If your graphics board is supported by any of the "ordinary" servers, you should use one of those, not the framebuffer server.
One problem faced by the XFree86 developers is that some video card manufacturers use nonstandard mechanisms for determining clock frequencies used to drive the card. Some of these manufacturers either don't release specifications describing how to program the card or require developers to sign a nondisclosure statement to obtain the information. This would obviously restrict the free distribution of the XFree86 software, something that the XFree86 development team is not willing to do.
The suggested minimum setup for XFree86 under Linux is a 486 machine with at least 16 MB of RAM and a video card with a chipset listed earlier. For optimal performance, we suggest using an accelerated card, such as an S3-chipset card. You should check the documentation for XFree86 and verify that your particular card is supported before taking the plunge and purchasing expensive hardware. Benchmark ratings comparisons for various video cards under XFree86 are posted to the Usenet newsgroups comp.windows.x.i386unix and comp.os.linux.misc regularly.
As a side note, one author's (Kalle's) personal Linux system is an AMD K6-2 with 128 MB of RAM and is equipped with a PCI Permedia II chipset card with 8 MB of DRAM. This setup is already a lot faster with respect to display speed than many workstations. XFree86 on a Linux system with an accelerated SVGA card will give you much greater performance than that found on commercial nix workstations (which often employ simple frame buffers for graphics and provide accelerated graphics hardware only as a high-priced add-on).
Your machine will need at least 8 MB of physical RAM, and 16 MB of virtual RAM (for example, 8 MB physical and 8 MB swap). Remember that the more physical RAM you have, the less the system will swap to and from disk when memory is low. Because swapping is inherently slow (disks are very slow compared to memory), having 8 MB of RAM or more is necessary to run XFree86 comfortably. A system with 8 MB of physical RAM could run much more slowly (up to 10 times more slowly) than one with 16 MB or more.
The Linux binary distribution of XFree86 can be found on a number of FTP sites. On ftp://ftp.xfree86.org, it is found in the directory /pub/XFree86/126.96.36.199/binaries; there you will find systems for Intel, m68k, PPC, and Alpha AXP in subdirectories. (At the time of this writing, the current version is 188.8.131.52; newer versions are released periodically).
It's quite likely you obtained XFree86 as part of a Linux distribution, in which case downloading the software separately is not necessary. If you are downloading XFree86 directly, the following tables list the files in the XFree86-184.108.40.206 distribution.
One of the following servers is required (not all of those are available for all platforms, but all are available for Intel systems):
All of the following files are required:
The following files are optional:
The XFree86 directory should contain README files and installation notes for the current version.
Obtain these files and save them in the directory /var/tmp (you can use any other directory; just change the pathname accordingly in the following examples), and create the directory /usr/X11R6 as root. Copy the three files preinst.sh, postinst.sh and extract to /var/tmp. Change to the directory /usr/X11R6 and run:
Next, make sure the extract utility that you downloaded is executable:
chmod 755 extract
Now unpack the binaries by typing:
Finally, run the post-installation script:
You need to make sure that /usr/X11R6/bin is on your path. This can be done by editing your system default /etc/profile or /etc/csh.login (based on the shell that you or other users on your system, use). Or you can simply add the directory to your personal path by modifying /etc/.bashrc or /etc/.cshrc, based on your shell.
You also need to make sure that /usr/X11R6/lib can be located by ld.so, the runtime linker. To do this, add the line:
to the file /etc/ld.so.conf, and run /sbin/ldconfig as root./usr/X11R6/lib
Setting up XFree86 is not difficult in most cases. However, if you happen to be using hardware for which drivers are under development, or wish to obtain the best performance or resolution from an accelerated graphics card, configuring XFree86 can be somewhat time-consuming.
In this section, we describe how to create and edit the XF86Config file, which configures the XFree86 server. In many cases, it is best to start out with a "basic" XFree86 configuration - one that uses a low resolution. A good choice is 640x480, which should be supported on all video cards and monitor types. Once you have XFree86 working at a lower, standard resolution, you can tweak the configuration to exploit the capabilities of your video hardware. The idea is that you want to make sure XFree86 works at least minimally on your system and that something isn't wrong with your installation before attempting the sometimes difficult task of setting up XFree86 for real use. With current hardware, you should easily be able to get up to 1024x768 pixels.
But before you start to write a XF86Config file yourself, try one of the configuration programs that are available. In many cases, you can avoid going through the hassle that will be described on the next pages. Some programs that may help you are:
If one of these tools is able to configure your X server for you, you should use it and save yourself a lot of trouble. However, if all of the tools fail or if you really want to fine-tune your X server, you will have to know how to edit the XF86Config file yourself.
In addition to the information here, you should read the following documentation:
The main configuration file you need to create is /usr/X11R6/lib/X11/XF86Config (some distributions put this in /etc/XF86Config or /etc/X11 instead). This file contains information on your mouse, video card parameters, and so on. The file XF86Config.eg is provided with the XFree86 distribution as an example. Copy this file to XF86Config and edit it as a starting point.
The XF86Config manual page explains the format of this file in detail. Read this manual page now if you have not done so already.
We are going to present a sample XF86Config file, piece by piece. This file may not look exactly like the sample file included in the XFree86 distribution, but the structure is the same.
The XF86Config file format may change with each version of XFree86; this information is only valid for XFree86 Version 220.127.116.11.Also, you should not simply copy the configuration file listed here to your own system and attempt to use it. Attempting to use a configuration file that doesn't correspond to your hardware could drive the monitor at a frequency that is too high for it; there have been reports of monitors (especially fixed-frequency monitors) being damaged or destroyed by using an incorrectly configured XF86Config file. The bottom line is this: make absolutely sure your XF86Config file corresponds to your hardware before you attempt to use it.
Each section of the XF86Config file is surrounded
by the pair of lines
Section "Files" RgbPath "/usr/X11R6/lib/X11/rgb" FontPath "/usr/X11R6/lib/X11/fonts/misc/" FontPath "/usr/X11R6/lib/X11/fonts/75dpi/" EndSection
The next section is
Here, we have all lines within the section commented out.Section "ServerFlags" # Uncomment this to cause a core dump at the spot where a signal is # received. This may leave the console in an unusable state, but may # provide a better stack trace in the core dump to aid in debugging # NoTrapSignals # Uncomment this to disable the <Crtl><Alt><BS> server abort sequence # DontZap EndSection
The next section is
Other options are available as well: see the XF86Config file if you wish to modify the keyboard configuration. The previous example should work for most systems with U.S. keyboards. If you have another keyboard, you will have to add additional lines. For example, the following works for a standard German keyboard:Section "Keyboard" Protocol "Standard" AutoRepeat 500 5 ServerNumLock EndSection
XkbRules "xfree86" XkbModel "pc102" XkbLayout "de" XkbVariants "" XkbOptions ""
The next section is
The only options you should concern yourself with now areSection "Pointer" Protocol "MouseSystems" Device "/dev/mouse" # Baudrate and SampleRate are only for some Logitech mice # BaudRate 9600 # SampleRate 150 # Emulate3Buttons is an option for 2-button Microsoft mice # Emulate3Buttons # ChordMiddle is an option for some 3-button Logitech mice # ChordMiddle EndSection
Protocol specifies the
protocol your mouse uses (not the make
or brand of mouse). Valid types for
Linux - there are other options available for other operating
BusMouse should be used for the Logitech busmouse. Note that
older Logitech mice that are not bus mice should use
Logitech, but newer Logitech
mice that are not bus mice use either the
This is a case where the protocol doesn't necessarily have anything
to do with the make of the mouse.
If you have a modern serial mouse, you could also try to specify
It is easy to check whether you have selected the correct mouse driver once you have started up X; when you move your mouse, the mouse pointer on the screen should follow this movement. If it does this, your setup is very likely to be correct. If it doesn't, try another driver, and also check whether the device you specified is correct.
The next section is
Section "Monitor" Identifier "CTX 5468 NI" # These values are for a CTX 5468NI only! Don't attempt to use # them with your monitor (unless you have this model) HorizSync 30-38,47-50 VertRefresh 50-90 # Modes: Name dotclock horiz vert ModeLine "640x480" 25 640 664 760 800 480 491 493 525 ModeLine "800x600" 36 800 824 896 1024 600 601 603 625 ModeLine "1024x768" 65 1024 1088 1200 1328 768 783 789 818 EndSection
Your monitor manual should list these values in the technical specifications section. If you do not have this information, you should contact either the manufacturer or the vendor of your monitor to obtain it. There are other sources of information, as well; they are listed later.HorizSync 31.5, 35.2, 37.9, 35.5, 48.95
You should be careful with those settings. While the settings
name is an arbitrary string, which you will use to refer to the
resolution mode later in the file.
dot-clock is the driving
clock frequency or
dot clock associated with the resolution mode.
A dot clock is usually specified in MHz and is the rate at which the
video card must send pixels to the monitor at this resolution.
vert-values are four numbers each;
they specify when the electron gun of the monitor should fire and
when the horizontal and vertical sync pulses fire during a sweep across the screen.
How can you determine the
Two files included in the XFree86 distribution may include
You should start with
This is a VESA standard timing for a 640x480 video mode. It uses a dot clock of 25.175, which your video card must support to use this mode (more on this later).# 640x480@60Hz Non-Interlaced mode # Horizontal Sync = 31.5kHz # Timing: H=(0.95us, 3.81us, 1.59us), V=(0.35ms, 0.064ms, 1.02ms) # # name clock horizontal timing vertical timing flags "640x480" 25.175 640 664 760 800 480 491 493 525
To include this entry in the XF86Config file, you'd use the line:
ModeLine "640x480" 25.175 640 664 760 800 480 491 493 525
If the VESA standard timings do not work for you (you'll know after
trying to use them later when the screen is unsteady, flickers, or
shows snow), the files modeDB.txt and
Monitors include specific mode values for many monitor types.
You can create
If you are completely at a loss, and can't find working
Lastly, if you do obtain
values for monitors other than the model you own. If you attempt to
drive the monitor at a frequency for which it was not designed, you can
damage or even destroy it.
The next section of the XF86Config file is
Section "Device" Identifier "#9 GXE 64" # Nothing yet; we fill in these values later. EndSection
This section defines properties for a particular video card.
Initially, you don't need to include anything in the
Before we do this, however, we need to finish writing the
XF86Config file. The next section is
Section "Screen" Driver "Accel" Device "#9 GXE 64" Monitor "CTX 5468 NI" Subsection "Display" Depth 16 Modes "1024x768" "800x600" "640x480" ViewPort 0 0 Virtual 1024 768 EndSubsection EndSection
ln -s /usr/X11R6/bin/XF86_SVGA /usr/X11R6/bin/X
Of course, you have to replace the first pathname with that of another server binary if you don't use the SVGA server.
Therefore, we useIdentifier "#9 GXE 64"
"#9 GXE 64" on the
Device line here.
The options you should know about are:
Many other options for this section exist; see the XF86Config manual page for a complete description. In practice, these other options are not necessary to get XFree86 working initially.
Your XF86Config file is now ready to go with the exception of complete information on the video card. What we're going to do is use the X server to probe for the rest of this information and fill it into XF86Config.
Instead of probing for this information with the X server, you can find the XF86Config values for many cards in the files modeDB.txt, AccelCards, and Devices. These files are all in /usr/X11R6/lib/X11/doc. In addition, there are various README files for certain chipsets. You should look in these files for information on your video card, and use that information (the clock values, chipset type, and any options) in the XF86Config file. Unfortunately, some manufacturers put out a graphics board with a new chipset without changing the board's name. If any information is missing, you can probe for it as described here.
In these examples, we will demonstrate configuration for a #9 GXE 64 video card, which uses the XF86_S3 chipset. This card happens to be the one that used by one of the authors, but the discussion here applies to any video card.
The first thing to do is to determine the video chipset used on the card. Running SuperProbe (found in /usr/X11R6/bin) will tell you this information, but you need to know the chipset name as it is known to the X server.
To do this, run the command:
This lists the chipset names known to your X server. (The manual pages for each X server list these as well.) For example, with the accelerated XF86_S3 server, we obtain:#
XFree86 Version 18.104.22.168 / X Window System (protocol Version 11, revision 0, vendor release 6000) Release Date: March 2 1998 If the server is older than 6-12 months, or if your card is newer than the above date, look for a newer version before reporting problems. (see https://www.XFree86.Org/FAQ) Operating System: Linux 2.0.33 i686 [ELF] Configured drivers: S3: accelerated server for S3 graphics adaptors (Patchlevel 0) newmmio, mmio_928, s3_generic
The valid chipset names for this server are
If you don't know which chipset to use, the X server can probe it for you. To do this, run the command:
if you use bash as your shell. If you use csh, try:#
You should run this command while the system is unloaded, that is, while no other activity is occurring on the system. This command also probes for your video-card dot clocks (as seen later), and system load can throw off this calculation.
The output from this command (in /tmp/x.out) should contain lines such as the following:
Here, we see that the three valid chipsets for this server (XF86_S3) areXFree86 Version 22.214.171.124 / X Window System (protocol Version 11, revision 0, vendor release 6000) Operating System: Linux Configured drivers: S3: accelerated server for S3 graphics adaptors (Patchlevel 0) newmmio, mmio_928, s3_generic . . . (--) S3: card type: 386/486 localbus (--) S3: chipset: 864 rev. 0 (--) S3: chipset driver: mmio_928
server probed for and found a video card using the
mmio_928 chipset driver.
Section "Device" # We already had Identifier here... Identifier "#9 GXE 64" # Add this line: Chipset "mmio_928" EndSection
Now we need to determine which dot clocks are made available by the video card. First, you should look into the files (modeDB.txt and so forth) mentioned at the beginning of this section and see if your card's clocks are listed there. The dot clocks will usually be a list of 8 or 16 values, all of which are in MHz. For example, when looking at mode-DB.txt, we see an entry for the Cardinal ET4000 video board, which looks like this:
As we can see, the dot clocks for this card are 25, 28, 38, 36, 40, 45, 32, and 0 MHz.# chip RAM virtual clocks default-mode flags ET4000 1024 1024 768 25 28 38 36 40 45 32 0 "1024x768"
to theClocks 25 28 38 36 40 45 32 0
Devices section of the file, after
The order of the clocks is important! Don't re-sort the list
of clocks or remove duplicates.
If you cannot find the dot clocks associated with your card, the X server can probe for these as well. Using the X -probeonly command described earlier, the output should contain lines that look like the following:
We could then add a(--) S3: clocks: 25.18 28.32 38.02 36.15 40.33 45.32 32.00 00.00
Clocks line containing all of these values,
as printed. You can use more than one
Clocks line in
if all the values (sometimes there are more than eight clock values
printed) don't fit onto one line. Again, be sure to keep the list of clocks
in the order that they are printed.
Be sure there is no
Note that some accelerated video boards use a programmable clock chip. (See the XF86_Accel manual page for details; this generally applies to S3, AGX, and XGA-2 boards.) This chip essentially allows the X server to tell the card which dot clocks to use. If this is the case, you may not find a list of dot clocks for the card in any of the files mentioned earlier. Or the list of dot clocks printed when using X -probeonly will contain only one or two discrete clock values, with the rest being duplicates or zero.
For boards that use a programmable clock chip, you would use a
If you are not so lucky, the manual pages for each server describe the possible values for your server. For example, in the file README.S3, we see that several S3-864 video cards use an ICD2061A clock chip, and that we should use the line:
instead ofClockChip "icd2061a"
Clocks in the
XF86Config file. As with
Clocks, this line should go in the
Devices section after
Similarly, some accelerated cards require you to specify the RAMDAC chip
type in the XF86Config file, using a
Some video card types require you to specify several options in the
Usually, the X server works without these options, but they are necessary to obtain the best performance. There are too many such options to list here, and they each depend on the particular video card being used. If you must use one of these options, fear not: the X server manual pages and various files in /usr/X11R6/lib/X11/doc will tell you what they are.Option "number_nine"
So when you're finished, you should end up with a
ThisSection "Device" # Device section for the #9 GXE 64 only ! Identifier "#9 GXE 64" Chipset "mmio_928" ClockChip "icd2061a" Option "number_nine" EndSection
is valid only for a particular video card, the #9 GXE 64; it is
given here only as an example. Most video cards require a
Clocks line, instead of
There are other options you can include in the
With your XF86Config file configured, you're ready to fire up the X server and give it a spin. First, be sure that /usr/X11R6/bin is on your path.
The command to start up XFree86 is:
This is a frontend to xinit (in case you're used to using xinit on other Unix systems). You can still use xinit, which gives you precise control about what exactly is started but requires you to start all needed programs manually.startx
This command starts the X server and runs the commands found in the file .xinitrc in your home directory. .xinitrc is just a shell script containing X clients to run. If this file does not exist, the system default /usr/X11R6/lib/X11/xinit/xinitrc will be used.
You can change the initial display when starting up the X Window System by providing a different .xinitrc in your home directory. The next chapter tells you what you can put in this file.
If you are new to the X Window System environment, we strongly suggest picking up a book such as The X Window System User's Guide by Valerie Quercia and Tim O'Reilly.
Often, something will not be quite right when you initially fire up the
X server. This is almost always caused by a problem in your XF86Config
file. Usually, the monitor timing values are off or the video-card
dot clocks are set incorrectly. If your display seems to roll, or the edges
are fuzzy, this is a clear indication that the monitor timing values or
dot clocks are wrong. Also be sure you are correctly specifying
your video card chipset, as well as other options for the
If all else fails, try to start X "bare"; that is, use a command such as:
You can then kill the X server (using the Ctrl-Alt-Backspace key combination) and examine the contents of /tmp/x.out. The X server reports any warnings or errors - for example, if your video card doesn't have a dot clock corresponding to a mode supported by your monitor. This output can be very helpful in diagnosing all kinds of problems. Examine it closely if your X server does not start up at all, does not provide the resolutions you wanted, or shows a flaky, snowy, or otherwise insufficient picture. Even if everything works to your satisfaction, you might want to check this file for interesting information that the X server has found out about your hardware. The lines starting withX > /tmp/x.out 2>&1
(**) contain data that you provided yourself in the configuration file, while lines starting with
(--) contain data that the X server has found out itself.
The file VideoModes.doc included in the XFree86 distribution contains many hints for tweaking the values in your XF86Config file.
Remember that you can use Ctrl-Alt with the plus or minus on the numeric keypad to switch between the video modes
listed on the
Also, check the vertical and horizontal size/hold knobs on your monitor. In many cases it is necessary to adjust these when starting up X. For example, if the display seems to be shifted slightly to one side, you can usually correct this using the monitor controls.
The Usenet newsgroup comp.windows.x.i386unix is devoted to discussions about XFree86. It might be a good idea to watch that newsgroup for postings relating to your video configuration; you might run across someone with the same problems as your own. If this fails, please contact your Linux distributor; their support staff should be able to help you as well.
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