5.1 How To Compile Programs
Most Linux software is written in C and compiled with the GNU C compiler. GCC is a part of every Linux distribution. The latest compiler version, documentation, and patches are on ftp://ftp.gnu.org/pub/gnu/.
Programs that are written in C++ must be compiled with the GNU G++ compiler, which is also included in Linux distributions and available from the same place as GCC.
To build version 2.0.x kernels, you will need GCC version 2.7.2.x, approximately. Trying to build an early Linux kernel with a different compiler, like GCC 2.8.x, EGCS, or PGCC, may cause problems because of GCC related code dependencies. Kernel versions 2.3 and 2.4 should compile correctly with more recent compilers.
Information on the EGCS compiler is at http://www.gnu.org/software/gcc/gcc.html.
Note that at this time, the kernel developers are not answering bug
requests for earlier kernels, but instead are concentrating on
developing 2.4.x version kernels and maintaining 2.2.x version
kernels.
[J.H.M. Dassen, Axel Boldt]
5.2 How To Install GNU Software
On a correctly configured system, installing a GNU software package requires four steps:
* With the source.tar.gz archive in the /usr/src/ directory, or wherever you maintain your source files, untar and decompress the package with the command:
tar zxvf package-name.tar.gz
* Run the ./configure script in the untarred source archive's top-level directory with whatever command line arguments you need. The options that configure recognizes are usually contained in a file called INSTALL or README.
* Run make. This will build the source code into an executable program (or programs) and may take a few minutes or a few hours, depending on the speed of the computer and the size of the package.
* Run make install. This will install the compiled binaries, configuration files, and any libraries in the appropriate directories.
5.3 Where To Get Java
The Sun Microsystems Java runtime environments and developer's kits are at http://java.sun.com/java/.
You can also get the source code, which is licensed by Sun Microsystems.
The home page of IBM's Jikes Java compiler is http://www10.software.ibm.com/developerworks/opensource/jikes.
There is a version of Sun's HotJava browser for Linux at: http://www.java.sun.com/products/hotjava/.
Kaffee, a free Java clone, is available from: http://www.kaffe.org/.
There is a resource page of free and commercial Java packages at: http://www.blackdown.org/java-linux.html.
Netscape Communicator comes with its own version of the Java Runtime Environment, so if you need Java only to view Web graphics, you may already have the runtime version of the Java Virtual Machine and libraries that you need installed on your system. You can download Communicator from http://www.netscape.com/.
5.4 How To Port XXX to Linux
In general, *nix programs need very little porting. Simply follow the installation instructions. If you don't know--and don't know how to find out--the answers to some of the questions asked during the installation procedure, you can guess, but this tends to produce buggy programs. In this case, you're probably better off asking someone else to do the port. If you have a BSD-ish program, you should try using -I/usr/include/bsd and -lbsd on the appropriate parts of the compilation lines.
5.5 What Is ld.so and How To Get It?
ld.so is the dynamic library loader. Each binary using shared libraries used to have about 3K of start-up code to find and load the shared libraries. Now that code has been put in a special shared library, /lib/ld.so, where all binaries can look for it, so that it wastes less disk space, and can be upgraded more easily. ld.so can be obtained from http://tsx-11.mit.edu/pub/linux/packages/GCC/ and mirror sites. The latest version at the time of writing is ld.so.1.9.5.tar.gz. /lib/ld-linux.so.1 is the same thing for ELF ("What's all this about ELF? ") and comes in the same package as the a.out loader.
5.6 How To Upgrade the Libraries without Trashing the System
Warning
Note: You should always have a rescue disk set ready when you perform this procedure, in the likely event that something goes wrong!
This procedure is especially difficult if you're upgrading very old libraries like libc4. But you should be able to keep libc4 on the same system with libc5 libraries for the programs that still need them. The same holds true for upgrading from libc5 to the newer-yet glibc2 libraries.
The problem with upgrading dynamic libraries is that, the moment you remove the old libraries, the utilities that you need to upgrade to the new version of the libraries don't work. There are ways around around this. One is to temporarily place a spare copy of the run time libraries, which are in /lib/, in /usr/lib/, or /usr/local/lib/, or another directory that is listed in the /etc/ld.so.conf file.
For example, when upgrading libc5 libraries, the files in /lib/ might look something like:
libc.so.5 libc.so.5.4.33 libm.so.5 libm.so.5.0.9
These are the C libraries and the math libraries. Copy them to another directory that is listed in /etc/ld.so.conf, like /usr/lib/:
$ cp -df /lib/libc.so.5* /usr/lib/ $ cp -df /lib/libm.so.5* /usr/lib/ $ ldconfig
Be sure to run ldconfig to upgrade the library configuration.
The files libc.so.5 and libm.so.5 are symbolic links to the actual library files. When you upgrade, the new links will not be created if the old links are still there, unless you use the -f flag with cp. The -d flag to cp will copy the symbolic link itself, and not the file it points to.
If you need to overwrite the link to the library directly, use the -f flag with ln.
For example, to copy new libraries over the old ones, try this. Make a symbolic link to the new libraries first, then copy both the libraries and the links to /lib/, with the following commands:
$ ln -sf ./libm.so.5.0.48 libm.so.5 $ ln -sf ./libc.so.5.0.48 libc.so.5 $ cp -df libm.so.5* /lib $ cp -df libc.so.5* /lib
Again, remember to run ldconfig after you copy the libraries.
If you are satisfied that everything is working correctly, you can remove the temporary copies of the old libraries from /usr/lib/ or wherever you copied them.
5.7 How To Use Code or a Compiler Compiled for a 486 on a 386
Yes, unless it's the kernel.
The -m486 option to GCC, which is used to compile binaries for x486 machines, merely changes certain optimizations. This makes for slightly larger binaries that run somewhat faster on a 486. They still work fine on a 386, though, with a small performance hit.
However, from version 1.3.35 the kernel uses 486 or Pentium-specific instructions if configured for a 486 or Pentium, thus making it unusable on a 386.
GCC can be configured for a 386 or 486; the only difference is that configuring it for a 386 makes -m386 the default and configuring for a 486 makes -m486 the default. In either case, these can be overridden on a per-compilation basis or by editing /usr/lib/gcc-lib/i*-linux/ n.n.n/specs.
There is an alpha version of GCC that knows how to do optimization well for the 586, but it is quite unreliable, especially at high optimization settings. The Pentium GCC can be found on ftp://tsx-11.mit.edu/pub/linux/ALPHA/pentium-gcc/. The ordinary 486 GCC supposedly produces better code for the Pentium using the -m386, or at least slightly smaller.
5.8 What Does "gcc -O6" Do?
Currently, the same as -O2 (GCC 2.5) or -O3 (GCC 2.6, 2.7). Any number greater than that does the same thing. The Makefiles of newer kernels use -O2, and you should probably do the same.
5.9 Where Are linux/*.h and asm/*.h?
The files /usr/include/linux/ and /usr/include/asm/ are often soft links to the directories where the kernel headers are. They are usually under /usr/src/kernel*/.
If you don't have the kernel sources, download them. Refer to the answer: ("How To Upgrade/Recompile a Kernel.")
Then, use rm to remove any garbage, and ln to create the links:
$ rm -rf /usr/include/linux /usr/include/asm $ ln -sf /usr/src/linux/include/linux /usr/include/linux $ ln -sf /usr/src/linux/include/asm /usr/include/asm
/usr/src/linux/include/asm/ is a symbolic link to an architecture-specific asm directory. If you have a freshly unpacked kernel source tree, you must make symlinks. You'll also find that you may need to do `make config' in a newly-unpacked kernel source tree, to create linux/autoconf.h.
5.10 What To Do about Errors Trying to Compile the Kernel
See the previous question regarding the header files.
Remember that when you apply a patch to the kernel, you must use the "-p0" or "-p1" option: otherwise, the patch may be misapplied. See the patch manual page for details.
"ld: unrecognized option `-qmagic'" means that you should get a newer linker, from ftp://tsx-11.mit.edu/pub/linux/packages/GCC/, in the file binutils-2.8.1.0.1.bin.tar.gz.
5.11 How To Make a Shared Library
For ELF,
$ gcc -fPIC -c *.c $ gcc -shared -Wl,-soname,libfoo.so.1 -o libfoo.so.1.0 *.o
For a.out, get tools-n.nn.tar.gz from tsx-11.mit.edu/pub/linux/packages/GCC/src/. It comes with documentation that will tell you what to do. Note that a.out shared libraries are a very tricky business. Consider upgrading your libraries to ELF shared libraries. See the ELF HOWTO, at ftp://metalab.unc.edu/pub/Linux/docs/HOWTO/
5.12 Programs Are Very Large
With an ELF compiler ("What's All This about ELF? glibc?"), the most common cause of large executables is the lack of an appropriate .so library link for one of the libraries you're using. There should be a link like libc.so for every library like libc.so.5.2.18.
With an a.out compiler the most common cause of large executables is the -g linker (compiler) flag. This produces (as well as debugging information in the output file) a program which is statically linked--one which includes a copy of the C library instead of a dynamically linked copy.
Other things worth investigating are -O and -O2, which enable optimization (check the GCC documentation), and -s (or the strip command) which strip the symbol information from the resulting binary (making debugging totally impossible).
You may wish to use -N on very small executables (less than 8K with the -N), but you shouldn't do this unless you understand its performance implications, and definitely never with daemons.
5.13 Does Linux Support Threads or Lightweight Processes?
As well as the Unix multiprocessing model involving heavyweight processes, which is of course part of the standard Linux kernel, there are several implementations of lightweight processes or threads. Recent kernels implement a thread model, kthreads. In addition, there are the following packages available for Linux.
* GNU glibc2 for Linux has optional support for threads. The archive is available from the same place as glibc2, ftp://ftp.gnu.org/pub/gnu/
* In sipb.mit.edu:/pub/pthread/ or ftp.ibp.fr:/pub/unix/threads/pthreads. Documentation isn't in the package, but is available on the World Wide Web at http://www.mit.edu:8001/people/proven/home_page.html. Newer Linux libc's contain the pthreads source. The GNU Ada compiler on ftp://metalab.unc.edu/pub/Linux/devel/lang/ada/gnat-3.01-linux+elf .tar.gz contains binaries made from that source code.
* In ftp://ftp.cs.washington.edu:/pub/qt-001.tar.Z is QuickThreads. More information can be found in the technical report, available on the same site is /tr/1993/05/UW-CSE-93-05-06.PS.Z.
* In gummo.doc.ic.ac.uk/rex/ is lwp, a very minimal implementation.
* In ftp://ftp.cs.fsu.edu:/pub/PART/, an Ada implementation. This is useful mainly because it has a lot of Postscript papers that you'll find useful in learning more about threads. This is not directly usable under Linux.
Please contact the authors of the packages in question for details.
5.14 Where To Find lint for Linux
Roughly equivalent functionality is built into GCC. Use the -Wall option to turn on most of the useful extra warnings. See the GCC manual for more details (type F1-i in Emacs and select the entry for GCC).
There is a freely available program called lclint that does much the same thing as traditional lint. The announcement and source code are available at on ftp://larch.lcs.mit.edu/pub/Larch/lclint/; on the World Wide Web, look at http://lclint.cs.virginia.edu/.
5.15 Where To Find Kermit for Linux
Kermit is distributed under a non-GPL copyright that makes its terms of distribution somewhat different. The sources and some binaries are available on ftp://kermit.columbia.edu.
The WWW Home Page of the Columbia University Kermit project is http://www.columbia.edu/kermit/.
5.16 How To Use Linux with a Cable Modem
The www.CablemodemInfo.com and xDSL Web page at http://www.cablemodeminfo.com/ has a section devoted to Linux.
5.17 Is There an ICQ Program That Runs under Linux?
Several ICQ clients are available on metalab.unc.edu. (Refer to: "Where Are the Linux FTP Archives?") ICQ itself does not have a Linux client, but there is a Java client at http://www.mirabilis.com/download/.
6.1. FTP Transfers Seem to Hang
FTP transfers that die suddenly are due, apparently, to some form of overrunning buffer. It occurs both with Linux and Microsoft servers. On Linux systems, The problem seems to occur most commonly with the distribution's server software.
If you receive ftp: connection refused errors, then the problem is likely due to a lack of authentication. Refer to "FTP or Telnet Server Won't Allow Logins.."
One remedy is to be replacing the distribution FTP server with the Linux port of the OpenBSD FTP server. The home page is: http://www.eleves.ens.fr:8080/home/madore/programs/
To install the BSD server, follow the installation instructions, and refer to the manual pages for inetd and inetd.conf. (If you have the newer xinetd, see below.) Be sure to tell inetd to run the BSD daemon alone, not as a subprocess of, for example, tcpd. Comment out the line that begins "ftp" in the /etc/inetd.conf file and replace it with a line similar to (if you install the new ftpd in /usr/local/sbin/):
# Original entry, commented out. #ftp stream tcp nowait root /usr/sbin/tcpd /usr/sbin/in.ftpd # Replacement entry: ftp stream tcp nowait root /usr/local/sbin/ftpd -l The replacement daemon will become effective after rebooting or sending (as root) a SIGHUP to inetd, e.g.: # kill -HUP inetd
To configure xinetd, create an entry in /etc/xinetd.d per the instructions in the xinetd.conf manual page. Make sure, again, that the command-line arguments for ftpd are correct, and that you have installed the /etc/ftpusers and /etc/pam.d/ftp files. Then restart xinetd with the command: /etc/rc.d/init.d/xinetd restart. The command should report "OK," and the restart will be noted in the system message log.
6.2 Free Dumps Core
In Linux 1.3.57 and later, the format of /proc/meminfo was changed in a way that the implementation of free doesn't understand. Get the latest version, from metalab.unc.edu, in /pub/Linux/system/Status/ps/procps-0.99.tgz.
6.3 Netscape Crashes Frequently
Netscape shouldn't crash, if it and the network are properly configured. Some things to check:
* Make sure that the MOZILLA_HOME environment variable is correctly set. If you installed Netscape under /usr/local/netscape/, for example, that should be the value of MOZILLA_HOME. Set it from the command line (e.g, "export MOZILLA_HOME="/usr/local/netscape"" under bash or add it to one your personal or system initialization files. Refer to the manual page for your shell for details.
* If you have a brand-new version of Netscape, try a previous version, in case the run-time libraries are slightly incompatible. For example, if Netscape version 4.75 is installed (type "netscape --version" at the shell prompt), try installing version 4.7. All versions are archived at ftp://ftp.netscape.com/.
* Netscape uses its own Motif and Java Runtime Environment libraries. If a separate version of either is installed on your system, ensure that they aren't interfering with Netscape's libraries; e.g., by un-installing them.
* Make sure that Netscape can connect to its default name servers. The program will appear to freeze and time out after several minutes if it can't. This indicates a problem with the system's Internet connection; likely, the system can't connect to other sites, either.
6.4 FTP or Telnet Server Won't Allow Logins
This applies to server daemons that respond to clients, but don't
allow logins. On new systems that have Pluggable Authentication
Modules installed, look for a file named, "ftp," or "telnet," in the
directory /etc/pam/ or /etc/pam.d/. If the corresponding
authentication file doesn't exist, the instructions for configuring
FTP and Telnet authentication and other PAM configuration, should be
in /usr/doc/pam-
If it's an FTP server on an older system, make sure that the account exists in /etc/passwd, especially "anonymous."
This type of problem may also be caused a failure to resolve the host addresses properly, especially if using Reverse Address Resolution Protocol (RARP). The simple answer to this is to list all relevant host names and IP addresses in the /etc/hosts files on each machine. ( Refer to the example /etc/hosts and /etc/resolv.conf files in: "Sendmail Pauses for Up to a Minute at Each Command..") If the network has an internal DNS, make sure that each host can resolve network addresses using it.
If the host machine doesn't respond to FTP or Telnet clients at all, then the server daemon is not installed correctly, or at all. Refer to the manual pages: inetd and inetd.conf on older systems, or xinetd and xinetd.conf, as well as ftpd, and telnetd.
6.5 How To Keep Track of Bookmarks in Netscape?
This probably applies to most other browsers, too. In the Preferences/Navigator menu, set your home page to Netscape's bookmarks.html file, which is located in the .netscape (with a leading period) subdirectory. For example, if your login name is "smith," set the home page to:
file://home/smith/.netscape/bookmarks.html
Setting up your personal home page like this will present you with a nicely formatted (albeit possibly long) page of bookmarks when Netscape starts. And the file is automatically updated whenever you add, delete, or visit a bookmarked site.
6.6 The Computer Has the Wrong Time
There are two clocks in your computer. The hardware (CMOS) clock runs even when the computer is turned off, and is used when the system starts up and by DOS (if you use DOS). The ordinary system time, shown and set by date, is maintained by the kernel while Linux is running.
You can display the CMOS clock time, or set either clock from the other, with /sbin/clock (now called hwclock in many distributions). Refer to: man 8 clock or man 8 hwclock.
There are various other programs that can correct either or both clocks for system drift or transfer time across the network. Some of them may already be installed on your system. Try looking for adjtimex (corrects for drift), Network Time Protocol clients like netdate, getdate, and xntp, or NTP client-server suite like chrony. Refer to: "How to Find a Particular Application.."
6.7 Setuid Scripts Don't Seem to Work
That's right. This feature has been disabled in the Linux kernel on purpose, because setuid scripts are almost always a security hole. Sudo and SuidPerl can provide more security than setuid scripts or binaries, especially if execute permissions are limited to a certain user ID or group ID.
If you want to know why setuid scripts are a security hole, read the FAQ for comp.unix.questions.
6.8 Free Memory as Reported by free Keeps Shrinking
The "free" figure printed by free doesn't include memory used as a disk buffer cache--shown in the "buffers" column. If you want to know how much memory is really free add the "buffers" amount to "free." Newer versions of free print an extra line with this info.
The disk buffer cache tends to grow soon after starting Linux up. As you load more programs and use more files, the contents get cached. It will stabilize after a while.
6.9 When Adding More Memory, the System Slows to a Crawl
This is a common symptom of a failure to cache the additional memory. The exact problem depends on your motherboard.
Sometimes you have to enable caching of certain regions in your BIOS setup. Look in the CMOS setup and see if there is an option to cache the new memory area which is currently switched off. This is apparently most common on a '486.
Sometimes the RAM has to be in certain sockets to be cached.
Sometimes you have to set jumpers to enable caching.
Some motherboards don't cache all of the RAM if you have more RAM per amount of cache than the hardware expects. Usually a full 256K cache will solve this problem.
If in doubt, check the manual. If you still can't fix it because the documentation is inadequate, you might like to post a message to comp.os.linux.hardware giving all of the details--make, model number, date code, etc., so other Linux users can avoid it.
6.10 Some Programs (E.g. xdm) Won't Allow Logins
You are probably using non-shadow password programs and are using shadow passwords.
If so, you have to get or compile a shadow password version of the programs in question. The shadow password suite can be found at ftp://tsx-11.mit.edu:/pub/linux/sources/usr.bin/shadow/. This is the source code. The binaries are probably in linux/binaries/usr.bin/.
6.11 Some Programs Allow Logins with No Password
You probably have the same problem as in ("Some Programs (E.g. xdm) Won't Allow Logins."), with an added wrinkle.
If you are using shadow passwords, you should put a letter `x' or an asterisk in the password field of /etc/passwd for each account, so that if a program doesn't know about the shadow passwords it won't think it's a passwordless account and let anyone in.
6.12 The Machine Runs Very Slowly with GCC / X / ...
You may have too little real memory. If you have less RAM than all the programs you're running at once, Linux will swap to your hard disk instead and thrash horribly. The solution in this case is to not run so many things at once or buy more memory. You can also reclaim some memory by compiling and using a kernel with less options configured. See ("How To Upgrade/Recompile a Kernel.")
You can tell how much memory and swap you're using with the free command, or by typing:
$ cat /proc/meminfo
If your kernel is configured with a RAM disk, this is probably wasted space and will cause things to go slowly. Use LILO or rdev to tell the kernel not to allocate a RAM disk (see the LILO documentation or type "man rdev").
6.13 System Only Allows Root Logins
You probably have some permission problems, or you have a file /etc/nologin.
In the latter case, put "rm -f /etc/nologin" in your /etc/rc.local or /etc/rc.d/* scripts.
Otherwise, check the permissions on your shell, and any file names that appear in error messages, and also the directories that contain these files, up to and including the root directory.
6.14 The Screen Is All Full of Weird Characters Instead of Letters.
You probably sent some binary data to your screen by mistake. Type echo '\033c' to fix it. Many Linux distributions have a command, reset, that does this.
If that doesn't help, try a direct screen escape command.
$ echo 'Ctrl-V Ctrl-O'
This resets the default font of a Linux console. Remember to hold down the Control key and type the letter, instead of, for example, Ctrl, then V. The sequence
$ echo 'Ctrl-V Esc C'
causes a full screen reset. If there's data left on the shell command line after typing a binary file, press Ctrl-C a few times to restore the shell command line.
Another possible command is an alias, "sane," that can work with generic terminals:
$ alias sane='echo -e "\\033c";tput is2; \ > stty sane line 1 rows $LINES columns $COLUMNS'
The alias is enclosed with open quotes (backticks), not single quotes. The line break is included here for clarity, and is not required.
Make sure that $LINES and $COLUMNS are defined in the environment with a command similar to this in ~/.cshrc or ~/.bashrc,
$ LINES=25; export $LINES; $COLUMNS=80; export $COLUMNS
using the correct numbers of $LINES and $COLUMNS for the terminal.
Finally, the output of "stty -g" can be used to create a shell script that will reset the terminal:
Save the output of "stty -g" to a file. In this example, the file is named "termset.":
$ stty -g >termset
The output of "stty -g" (the contents of "termset") will look something like:
500:5:bd:8a3b:3:1c:7f:15:4:0:1:0:11:13:1a:0:12:f:17:16:0:0:73
Edit "termset" to become a shell script; adding an interpreter and "stty" command:
#!/bin/bash stty 500:5:bd:8a3b:3:1c:7f:15:4:0:1:0:11:13:1a:0:12:f:17:16:0:0:73
Add executable permissions to "termset" and use as a shell script:
$ chmod +x termset $ ./termset
[Floyd L. Davidson, Bernhard Gabler]
Another way to accomplish normal characters again is to type:
$ tput reset
and then, of course tap Return or Enter.
Note: You will have to tap your keyboard blindly.
[gwl]
6.15 I Screwed Up the System and Can't Log In to Fix It
Reboot from an emergency floppy or floppy pair. For example, the Slackware boot and root disk pair in the install subdirectory of the Slackware distribution.
There are also two, do-it-yourself rescue disk creation packages in ftp://metalab.unc.edu/pub/Linux/system/recovery/. These are better because they have your own kernel on them, so you don't run the risk of missing devices and file systems.
Get to a shell prompt and mount your hard disk with something like
$ mount -t ext2 /dev/hda1 /mnt
Then your file system is available under the directory /mnt and you can fix the problem. Remember to unmount your hard disk before rebooting (cd somewhere else first, or it will say it's busy).
6.16 I Forgot the root Password
Note: Incorrectly editing any of the files in the /etc/ directory can severely screw up a system. Please keep a spare copy of any files in case you make a mistake.
If your Linux distribution permits, try booting into single-user mode by typing "single" at the BOOT lilo: prompt. With more recent distributions, you can boot into single-user mode when prompted by typing "linux 1," "linux single," or "init=/bin/bash."
If the above doesn't work for you, boot from the installation or rescue floppy, and switch to another virtual console with Alt-F1 -- Alt-F8, and then mount the root file system on /mnt. Then proceed with the steps below to determine if your system has standard or shadow passwords, and how to remove the password.
Using your favorite text editor, edit the root entry of the /etc/passwd file to remove the password, which is located between the first and second colons. Do this only if the password field does not contain an "x," in which case see below.
root:Yhgew13xs:0:0: ...
Change that to:
root::0:0: ...
If the password field contains an "x," then you must remove the
password from the /etc/shadow file, which is in a similar format.
Refer to the manual pages: "man passwd," and "man 5 shadow."
[Paul Colquhuon, Robert Kiesling, Tom Plunket]
6.17 There's a Huge Security Hole in rm!
No there isn't. You are obviously new to unices and need to read a good book to find out how things work. Clue: the ability to delete files depends on permission to write in that directory.
6.18 lpr and/or lpd Don't Work
First make sure that your /dev/lp* port is correctly configured. Its IRQ (if any) and port address need to match the settings on the printer card. You should be able to dump a file directly to the printer:
$ cat the_file >/dev/lp1
If lpr gives you a message like myname@host: host not found" it may mean that the TCP/IP loopback interface, lo, isn't working properly. Loopback support is compiled into most distribution kernels. Check that the interface is configured with the ifconfig command. By Internet convention, the network number is 127.0.0.0, and the local host address is 127.0.0.1. If everything is configured correctly, you should be able to telnet to your own machine and get a login prompt.
Make sure that /etc/hosts.lpd contains the machine's host name.
If your machine has a network-aware lpd, like the one that comes with LPRng, make sure that /etc/lpd.perms is configured correctly. Also look at the Printing HOWTO. "Where can I get the HOWTO's and other documentation? ".
6.19 Timestamps on Files on MS-DOS Partitions Are Set Incorrectly
There is a bug in the program clock (often found in /sbin). It miscounts a time zone offset, confusing seconds with minutes or something like that. Get a recent version.
6.20 How To Get LILO to Boot the Kernel Image
>From kernel versions 1.1.80 on, the compressed kernel image, which is what LILO needs to find, is in arch/i386/boot/zImage, or arch/i386/boot/bzImage when it is built, and is normally stored in the /boot/ directory. The /etc/lilo.conf file should refer to the vmlinuz symbolic link, not the actual kernel image.
This was changed to make it easier to build kernel versions for several different processors from one source tree.
6.21 How To Make Sure the System Boots after Re-Installing the Operating System
This should work whether you're re-installing Linux or some other, commercial, operating system:
* Insert a blank, formatted floppy in drive A:
* Save a copy of the boot hard drive's Master Boot Record to the floppy, by executing the command:
#dd if=/dev/hda of=/dev/fd0 count=1
dd is a standard program on Linux systems. A MS-Windows compatible version is available from ftp://ftp.gnu.org/, as well as many MS software archives.
* Test that the floppy boots the system by rebooting with the floppy in the A: drive.
* Then you should be able to install the other operating system (on a different hard drive and/or partition, if you don't want to uninstall Linux).
* After installation, boot Linux again from the floppy, and re-install the MBR with the command: /sbin/lilo.
[Jacques Guy]
6.22 The PCMCIA Card Doesn't Work after Upgrading the Kernel
The PCMCIA Card Services modules, which are located in /lib/modules/version/pcmcia, where version is the version number of the kernel, use configuration information that is specific to that kernel image only. The PCMCIA modules on your system will not work with a different kernel image. You need to upgrade the PCMCIA card modules when you upgrade the kernel.
When upgrading from older kernels, make sure that you have the most recent version of the run-time libraries, the modutils package, and so on. Refer to the file Documentation/Changes in the kernel source tree for details.
Important: If you use the PCMCIA Card Services, do not enable the Network device support/Pocket and portable adapters option of the kernel configuration menu, as this conflicts with the modules in Card Services.
Knowing the PCMCIA module dependencies of the old kernel is useful. You need to keep track of them. For example, if your PCMCIA card depends on the serial port character device being installed as a module for the old kernel, then you need to ensure that the serial module is available for the new kernel and PCMCIA modules as well.
The procedure described here is somewhat kludgey, but it is much easier than re-calculating module dependencies from scratch, and making sure the upgrade modules get loaded so that both the non-PCMCIA and PCMCIA are happy. Recent kernel releases contain a myriad of module options, too many to keep track of easily. These steps use the existing module dependencies as much as possible, instead of requiring you to calculate new ones.
However, this procedure does not take into account instances where module dependencies are incompatible from one kernel version to another. In these cases, you'll need to load the modules yourself with insmod, or adjust the module dependencies in the /etc/conf.modules file. The Documentation/modules.txt file in the kernel source tree contains a good description of how to use the kernel loadable modules and the module utilities like insmod, modprobe, and depmod. Modules.txt also contains a recommended procedure for determining which features to include in a resident kernel, and which to build as modules.
Essentially, you need to follow these steps when you install a new kernel.
* Before building the new kernel, make a record with the lsmod command of the module dependencies that your system currently uses. For example, part of the lsmod output might look like this:
Module Pages Used by memory_cs 2 0 ds 2 [memory_cs] 3 i82365 4 2 pcmcia_core 8 [memory_cs ds i82365] 3 sg 1 0 bsd_comp 1 0 ppp 5 [bsd_comp] 0 slhc 2 [ppp] 0 serial 8 0 psaux 1 0 lp 2 0
This tells you for example that the memory_cs module needs the ds and pcmcia_core modules loaded first. What it doesn't say is that, in order to avoid recalculating the module dependencies, you may also need to have the serial, lp, psaux, and other standard modules available to prevent errors when installing the pcmcia routines at boot time with insmod. A glance at the /etc/modules file will tell you what modules the system currently loads, and in what order. Save a copy of this file for future reference, until you have successfully installed the new kernel's modules. Also save the lsmod output to a file, for example, with the command: lsmod >lsmod.old-kernel.output.
* Build the new kernel, and install the boot image, either zImage or bzImage, to a floppy diskette. To do this, change to the arch/i386/boot directory (substitute the correct architecture directory if you don't have an Intel machine), and, with a floppy in the diskette drive, execute the command:
$ dd if=bzImage of=/dev/fd0 bs=512
if you built the kernel with the make bzImage command, and if your floppy drive is /dev/fd0. This results in a bootable kernel image being written to the floppy, and allows you to try out the new kernel without replacing the existing one that LILO boots on the hard drive.
* Boot the new kernel from the floppy to make sure that it works.
* With the system running the new kernel, compile and install a current version of the PCMCIA Card Services package, available from metalab.unc.edu as well as other Linux archives. Before installing the Card Services utilities, change the names of /sbin/cardmgr and /sbin/cardctl to /sbin/cardmgr.old and /sbin/cardctl.old. The old versions of these utilities are not compatible with the replacement utilities that Card Services installs. In case something goes awry with the installation, the old utilities won't be overwritten, and you can revert to the older versions if necessary. When configuring Card Services with the "make config" command, make sure that the build scripts know where to locate the kernel configuration, either by using information from the running kernel, or telling the build process where the source tree of the new kernel is. The "make config" step should complete without errors. Installing the modules from the Card Services package places them in the directory /lib/modules/version/pcmcia, where version is the version number of the new kernel.
* Reboot the system, and note which, if any, of the PCMCIA devices work. Also make sure that the non-PCMCIA hardware devices are working. It's likely that some or all of them won't work. Use lsmod to determine which modules the kernel loaded at boot time, and compare it with the module listing that the old kernel loaded, which you saved from the first step of the procedure. (If you didn't save a listing of the lsmod output, go back and reboot the old kernel, and make the listing now.)
* When all modules are properly loaded, you can replace the old kernel image on the hard drive. This will most likely be the file pointed to by the /vmlinuz symlink. Remember to update the boot sector by running the lilo command after installing the new kernel image on the hard drive.
Also look at the questions, How do I upgrade/recompile my kernel? and Modprobe can't locate module, "XXX," and similar messages.
6.23 How To Remove (or Change) the Colors in the ls Display
The shell command, "unalias ls," should completely unset the configuration that some distributions provide as standard. To change the colors, refer to the ls man page ("man ls").
6.24 Why Won't a Program Work in the Current Directory?
Because the current directory (i.e., ".") is not in the search path, for security reasons, as well as to insure that the correct program versions are used. If an intruder is able to write a file to a world-writable directory, like /tmp, presumably he or she would be able to execute it if the directory were in the search path. The solution to this is to include the directory in the command; e.g., "./myprog," instead of "myprog." Or add the current directory to your PATH environment variable; e.g., "export PATH=".:"$PATH" using bash, although this is discouraged for the reasons mentioned above.
7.1. How To Find Out If a Notebook Runs Linux
There's no fixed answer to this question, because notebook hardware is constantly updated, and getting the X display, sound, PCMCIA, modem, and so forth, working, can take a good deal of effort.
Most notebooks currently on the market, for example, use "Winmodems," which often do not work with Linux because of their proprietary hardware interfaces. Even notebooks which are certified as "Linux compatible," may not be completely compatible.
Information about installing Winmodems in general is contained in the Winmodems-and-Linux HOWTO. (Refer to "Where Is the Documentation?")
You can find the most current information, or ask other users about their notebook experiences, on the linux-laptop mailing list, which is hosted by the vger.redhat.com server. (Refer to "What Mailing Lists Are There?")
A mailing list for Linux on IBM Thinkpads has its home page at http://www.topica.com/lists/linux-thinkpad/.
Another Thinkpad mailing list is hosted by http://www.bm-soft.com/. Send email with the word "help" in the body of the message to majordomo@www.bm-soft.com.
There is a Web page about Linux on IBM Thinkpads at http://peipa.essex.ac.uk/tp-linux/.
The Linux Laptop home page is at http://www.cs.utexas.edu/users/kharker/linux-laptop/.
For information about interfacing peripherals like Zip and CD-ROM drives through parallel ports, refer to the Linux Parallel Port Home Page, at http://www.torque.net/linux-pp.html.
If you need the latest version of the PCMCIA Card Services package, it is (or was) located at ftp://cb-iris.stanford.edu/pub/pcmcia/, but that host no longer seems to be available. Recent distributions are on ftp://metalab.unc.edu/pub/Linux/kernel/pcmcia/. You will also need to have the kernel source code installed as well. Be sure to read the PCMCIA-HOWTO, which is included in the distribution.
7.2. Installing Linux Using FTP
Most distributions are too large and complex to make FTP installation practical. Installing a basic Linux system that doesn't have a GUI or major applications is possible with FTP, however. The main non-commercial distribution in use is Debian GNU/Linux, and this answer describes an installation of a basic Debian system, to which you can add other Linux applications and commercial software as necessary.
This answer describes installation on IBM-compatible machines with an Intel x86 or Pentium processor. You will need a machine with at least a 80386 processor, 8 Mb of memory, and about 100 Mb of disk space. More memory and a larger disk is necessary however, for practical everyday use.
For other hardware, substitute "-arm," "-ppc," "-m68k," or other abbreviation in directory names for "-i386."
For detailed and hardware-specific information refer to: http://www.debian.org/releases/stable/.
* Connect using anonymous FTP to ftp.debian.org and cd to the pub/debian/dists/stable/main/disks-i386/current/ subdirectory.
* Retrieve the binary image files for the rescue disk, and the drivers disk. Depending on the floppy drive installed on your machine, retrieve either the diskette images with "1200" in the names if you have a 1.2 Mb, 5.25-in. floppy, or the disks with "1440" in the name if the computer has a 3.25-in., 1.44 Mb floppy. Then retrieve the base system diskettes. Note that there are 7 base system images in the 1.44-Mb set (which have a "14" in their names) , and 9 in the 1.2-Mb set of images (which have a "12" in their names). You will use these to create the basic installation diskettes. If you have a Linux machine, you can use dd to write the images to the diskettes. If you are creating the installation diskettes on a MS-DOS machine, also download the RAWRITE.EXE MS-DOS utility, which will copy the raw binary images to floppy disks. Also download the install.en.txt document, which contains the detailed installation instructions.
* Create the installation disk set on floppies using either dd under Linux (e.g.: "dd if=resc1440.bin of=/dev/fd0"), or the RAWRITE.EXE utility under MS-DOS. Be sure to label each installation diskette.
* Insert the rescue diskette into the floppy drive and reboot the computer. If all goes well, the Linux kernel will boot, and you will be able start the installation program by pressing Enter at the boot: prompt.
* Follow the on-screen instructions for partitioning the hard disk, installing device drivers, the basic system software, and the Linux kernel. If the machine is connected to a local network, enter the network information when the system asks for it.
* To install additional software over the Internet, be sure that you have installed the ppp module during the installation process, and run (as root) the /usr/sbin/pppconfig utility. You will need to provide your user name with your ISP, your password, the ISP's dial-up phone number, the address(es) of the ISP's Domain Name Service, and the serial port that your modem is connected to, /dev/ttyS0-/dev/ttyS3. Be sure also to specify the defaultroute option to the PPP system, so the computer knows to use the PPP connection for remote Internet addresses.
* You may have to perform additional configuration on the PPP scripts in the /etc/ppp subdirectory, and in particular, the ISP-specific script in the /etc/ppp/peers subdirectory. There are basic instructions in each script. For detailed information, refer to the Debian/GNU Linux installation instructions that you downloaded, the pppd manual page (type man pppd), and the PPP HOWTO from the Linux Documentation project, http://www.linuxdoc.org/.
* Once you have a PPP connection established with your ISP (it will be displayed in the output of ifconfig), use the dselect program to specify which additional software you want to install. Use the apt [A]ccess option to retrieve packages via anonymous FTP, and make sure to use the [U]pdate option to retrieve a current list of packages from the FTP archive.
7.3 Resuming an Interrupted Download
You can use the "reget" command of the standard ftp client program after reconnecting to pick up where you left off.
Clients like ncftp support resumed FTP downloads, and wget supports resumed FTP and HTTP downloads.
7.4. Boot-Time Configuration
You can configure Linux at the lilo: prompt either by typing the kernel arguments at the BOOT lilo: prompt, or by adding an "append=" directive to the /etc/lilo.conf file; for example:
# At the LILO prompt (example only): BOOT lilo: parport=0x3bc,7 parport=0x3bc,none serial=0x3f8,4 serial=0x2f8,3 # Example statement for /etc/lilo.conf: append="parport=0x3bc,none serial=0x3f8,4 serial=0x2f8,3"
If you modify the /etc/lilo.conf file, be sure to run the lilo command to install the new configuration.
Configuration notes for specific hardware devices are in the documentation of the kernel source distribution, /usr/src/linux/Documentation in most distributions.
Refer to the lilo and /etc/lilo.conf manual pages, as well as the LDP BootPrompt-HowTo ("Where Is the Documentation?"), and the documentation in /usr/doc/lilo.
7.5. Formatting Man Pages without man or groff
The man2html program translates groff text to HTML, which you can view with a Web browser. The man2html program, and many like it, are availble on the Web. Look for them with your favorite search engine.
The unformatted manual pages are stored in subdirectories of /usr/man, /usr/local/man, and elsewhere.
If you want to view text, use nroff and less. Both of these programs have MSDOS versions with an implementation of the man macro package available as well. An example would be:
$ nroff -man /usr/man/man1/ls.1 | less
If you know where to find a good implementation of the man macros without installing groff, please let the FAQ maintainer know.
If the manual page filename ends in ".gz," then you'll need to uncompress it before formatting it, using gzip -d or gunzip. A one-line example would be:
$ gzip -dc /usr/man/man1/ls.1.gz | nroff -man | less
7.6. How To Scroll Backwards in Text Mode
With the default US keymap, you can use Shift with the PgUp and PgDn keys. (The gray ones, not the ones on the numeric keypad.) With other keymaps, look in /usr/lib/keytables. You can remap the ScrollUp and ScrollDown keys to be whatever you like.
The screen program, http://vector.co.jp/vpack/browse/person/an010455.html provides a searchable scrollback buffer and the ability to take "snapshots" of text-mode screens.
Recent kernels that have the VGA Console driver can use dramatically more memory for scrollback, provided that the video card can actually handle 64 kb of video memory. Add the line:
#define VGA_CAN_DO_64B
to the start of the file drivers/video/vgacon.c. This feature may become a standard setting in future kernels. If the video frame buffer is also enabled in the kernel, this setting may not affect buffering.
In older kernels, the amount of scrollback is fixed, because it is
implemented using the video memory to store the scrollback text. You
may be able to get more scrollback in each virtual console by reducing
the total number of VC's. See linux/tty.h.
[Chris Karakas]
7.7 How To Get Email to Work
For sending mail via SMTP (Simple Mail Transfer Protocol) and receiving mail from an ISP's POP (Post Office Protocol) server, you can use a desktop client like Netscape Communicator or KDE kmail. You will need to enter the names of the SMTP and POP servers in the preferences of the respective application, as well as your E-mail address (username@isp's-domain-name), and your dial-up password. The same applies to Usenet News. Enter the name of the NNTP (Network News Transfer Protocol) server in your News client's preferences section. You may also have to provide the IP addresses of the ISP's primary and secondary name servers.
If you have a traditional MTA (Mail Transport Agent) like Sendmail, Smail, qmail, or Exim, you'll need to follow the instructions in each package. Basically, configuration entails determining which host machine, either on your local LAN or via dial-up Internet, is the "Smart Host," if you're using SMTP. If you're using the older UUCP protocol, then you'll need to consult the directions for configuring UUCP, and also make sure that your ISP's system is configured to relay mail to you.
Information about Internet hosting, and News and E-mail in general, is available on the Usenet News group news.announce.newusers, and those FAQ's are also archived at ftp://rtfm.mit.edu/pub/usenet/.
7.8 Sendmail Pauses for Up to a Minute at Each Command
Make sure that Sendmail can resolve your hostname to a valid (i.e., parsable) domain address. If you are not connected to the Internet, or have a dial-up connection with dynamic IP addressing, add the fully qualified domain name to the /etc/hosts file, in addition to the base host name; e.g., if the host name is "bilbo" and the domain is "bag-end.com:"
192.168.0.1 bilbo.bag-end.com bilbo
And make sure that either the /etc/host.conf or /etc/resolv.conf file contains the line:
order hosts,bind
Caution: Do not change the "localhost" entry in /etc/hosts, because many programs depend on it for internal message-passing.
Sendmail takes many factors into account when resolving domain addresses. These factors, collectively, are known as, "rulesets," in sendmail jargon. The program does not require that a domain address be canonical, or even appear to be canonical. In the example above, "bilbo." (note the period) would work just as well as "bilbo.bag-end.com." This and other modifications apply mainly to recent versions.
Prior to version 8.7, sendmail required that the FQDN appear first in the /etc/hosts entry. This is due to changes in the envelope address masquerade options. Consult the sendmail documents.
If you have a domain name server for only a local subnet, make sure that "." refers to a SOA record on the server machine, and that reverse lookups (check by using nslookup) work for all machines on the subnet.
Finally, FEATURE configuration macro options like nodns, always_add_domain, and nocanonify, control how sendmail interprets host names.
The document, Sendmail: Installation and Operation Guide, included in
the doc/ subdirectory of Sendmail source code distributions, discusses
briefly how Sendmail resolves Internet addresses. Sendmail source code
archives are listed at: http://www.sendmail.org/
[Chris Karakas]
7.9 How To Enable and Select Virtual Consoles
In text mode, press the left Alt-F1 to Alt-F12 to select the consoles tty1 to tty12; Right Alt-F1 gives tty13 and so on. To switch out of X you must press Ctrl-Alt-F1, etc; Alt-F5 or whatever will switch back.
However, If you have a non-PC compatible system, please see the note below.
If you want to use a VC for ordinary login, it must be listed in /etc/inittab, which controls which terminals and virtual consoles have login prompts. The X Window System needs at least one free VC in order to start.
[Note: The key sequence is actually Ctrl--Meta-- FN. On PC compatible
systems, the right and left Alt keys are really synonymous with the
keysymbols Meta_L and Meta_R. If the binding is different, you can
determine what keys produce Meta_L and Meta_R with xkeycaps or a
similar application.]
[David Charlap]
7.10 How To Set the Time Zone
Change directory to /usr/lib/zoneinfo/. Get the time zone package if you don't have this directory. The source is available in ftp://metalab.unc.edu/pub/Linux/system/admin/time/.
Then make a symbolic link named localtime pointing to one of the files in this directory (or a subdirectory), and one called posixrules pointing to localtime. For example:
$ ln -sf US/Mountain localtime $ ln -sf localtime posixrules
This change will take effect immediately--try date.
If the system uses Red Hat-style configuration files, the respective time zone info files are /usr/share/zoneinfo and /etc/localtime.
The manual pages for tzset or tzselect describe setting the time zone. Some programs recognize the "TZ" environment variable, but this is not POSIX-correct.
You should also make sure that your Linux kernel clock is set to the correct GMT time. Type date -u and check that the correct UTC time is displayed. ("The Computer Has the Wrong Time.")
7.11 Dial-up PPP Configuration
This information is mainly for people who do not have a wrapper utility like kppp or pppconfig, or are not able to get those utilities to work correctly. If you need to manually configure PPP to dial in to your ISP, you will need the following information:
* The port that your modem is connected to: /dev/ttyS0-/dev/ttyS3, which correspond to COM1-COM4 under MS-DOS.
* The phone number of your ISP's data connection.
* The user name and password that your ISP gave you.
* The IP addresses of the primary and possibly secondary Domain Name Service that you will use when dialing in to the ISP. This assumes that you will not be using a DNS that you installed on your system.
When you have all of this information, make sure that the programs pppd and chat, at the very minimum, are installed correctly. In most current distributions, they are installed in the /usr/sbin/ directory, and you will need to be logged in as root to use them. In addition, the following programs are also useful for configuring network connections, determining network status, and diagnosing problems: /sbin/ifconfig, /sbin/route, /bin/ping, /usr/sbin/traceroute.
These are the basic steps that you need to follow to configure PPP. You must be logged in as root.
* Make sure that the serial port and modem are operating correctly. Using a program like minicomm or kermit, you should be able to send AT commands to the modem and receive the OK string in response from the modem.
* Enter the primary and possibly secondary Domain Name Server IP addresses in the /etc/resolv.conf file, using dotted quad notation, with the nameserver label. For example:
order hosts,bind nameserver 196.182.101.103 nameserver 196.182.101.104
The nameserver addresses in the example above are examples only. They don't correspond to actual network hosts. The first line, order hosts,bind, tells your networking software, when it resolves network domain addresses, to first look in the /etc/hosts file, and then use the bind service; i.e., the DNS servers, which are specified on the lines that begin with nameserver.
* Locate the chat script that PPP will use to dial the modem and connect to your ISP. In many systems, this is either in the /etc/chatscripts or /etc/ppp directory, and will be called provider or something similar. You can store a chat script anywhere, provided that you tell pppd to use it rather than the default script. Refer to the chat and pppd manual pages, and the information below, for details. Here is a sample chat script: