Subject: Linux Frequently Asked Questions with Answers (FAQ: 2/2)
From: [email-masked] (Ian Jackson)
Date: Sun, 10 Apr 1994 12:05:36 GMT
Newsgroups: comp.os.linux.announce,comp.os.linux.help,comp.answers,news.answers

Archive-Name: linux/faq/part2
Last-Modified: 10 Apr 1994

(Continued from part 1, where you'll find the introduction and
 table of contents.)
===============================================================================

Section 6.  Miscellaneous questions and problems

 Q6.1        How do I make my executables smaller ?
 Q6.2        How many people use Linux ?
 Q6.3        How can I get scrollback on text VC's ?
 Q6.4        Setuid scripts don't seem to work.
 Q6.5        Free memory as reported by free keeps shrinking.
 Q6.6        What is a BogoMip ?
 Q6.7        How do I set the timezone ?
 Q6.8        What version of Linux and what machine name am I using ?
 Q6.9        When I add more memory it slows to a crawl.
 Q6.10       Some programs (e.g. xdm) won't let me log in.
 Q6.11       Some programs let me log in with no password.
 Q6.12       My machine runs very slowly when I run GCC / X / ...
 Q6.13       I can only log in as root.
 Q6.14       How can I produce core files ?
 Q6.15       How do I stop producing core files ?
 Q6.16       My keyboard goes all funny after I switch VC's.
 Q6.17       My screen is all full of weird characters instead of letters.
 Q6.18       What is a .gz file ? And a .tgz ? And ... ?
 Q6.19       I have screwed up my system and can't log in to fix it.
 Q6.20       How do I upgrade/recompile my kernel ?
 Q6.21       Can I have more than 3 serial ports by sharing interrupts ?
 Q6.22       Emacs just dumps core.
 Q6.23       How do I make a bootable floppy ?
 Q6.24       How do I remap my keyboard to UK, French, etc. ?
 Q6.25       I've discovered a huge security hole in rm !
 Q6.26       lpr and lpd aren't working.
 Q6.27       How do I make a shared library ?
 Q6.28       What does VFS stand for ?

-------------------------------------------------------------------------------

Question 6.1.  How do I make my executables smaller ?

The most common cause of large executables is the -g compiler flag.  This
causes (as well as debugging information in the output file) the resulting
program to be linked statically, i.e. by including a copy of the C library
in it instead of using a dynamically linked copy.

Other things that are worth investigating are -O and -O2 which enable
optimisation (check the GCC documentation), -s which strips the symbol
information from the resulting binary (making debugging totally
impossible).

On very small executables you may wish to use -N, but you shouldn't do
this unless you understand its performance implications.

-------------------------------------------------------------------------------

Question 6.2.  How many people use Linux ?

Linux is freely available, and no one is required to register their copies
with any central authority, so it is difficult to know.  Several
businesses are now surviving solely on selling and supporting Linux, and
very few Linux users use those businesses, relatively speaking.  The Linux
newsgroups are some of the most heavily read on the Net, so the number is
likely in the hundreds of thousands, but firm numbers are hard to come by.

However, one brave soul, Harald T. Alvestrand
<[email-masked]>, has decided to try, and asks that if you
use Linux, you send a message to [email-masked] with one of the
following subjects: `I use Linux at home', `I use Linux at work', or `I
use Linux at home and at work'.  He will also accept `third-party'
registrations - ask him for details.  He posts his counts to
comp.os.linux.misc.

-------------------------------------------------------------------------------

Question 6.3.  How can I get scrollback on text VC's ?

With the default US keymap you can use Shift with the PageUp and PageDown
keys (NB these must be the grey ones, not the ones that are on the numeric
keypad !).  With other keymaps check the maps in /usr/lib/keytables; you
can remap the scroll up and down keys to be whatever you like --- for
example, in order to remap them to keys that exist on an 84-key AT
keyboard.

You can't increase the amount of scrollback, because of the way it is
implemented using the video memory to store the scrollback text, though
you may be able to get more scrollback in each VC by reducing the total
number of VC's --- see <linux/tty.h>.

-------------------------------------------------------------------------------

Question 6.4.  Setuid scripts don't seem to work.

That's right.  This feature has been specifically disabled in the Linux
kernel because setuid scripts are almost always a security hole.  If you
want to know why read the FAQ for comp.unix.questions.

-------------------------------------------------------------------------------

Question 6.5.  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'.

The disk buffer cache tends to grow soon after starting Linux up, as you
load more programs and use more files and the contents get cached.  It
will stabilise after a while.

-------------------------------------------------------------------------------

Question 6.6.  What is a BogoMip ?

`BogoMips' is a contraction of `Bogus MIPS'.  MIPS stands for (depending
who you listen to) Millions of Instructions per Second, or Meaningless
Indication of Processor Speed.

The number printed at boot-time is the result of a kernel timing
calibration, used for very short delay loops by some device drivers.

As a very approximate guide the BogoMips will be approximately:
          386SX               clock * 0.125 + 0.2
          386DX               clock * 0.20 - 0.6
          486SX/DX            clock * 0.49 + 0.25
          486DX2              clock * 0.50 + 0.37
          Pentium             24.0

If the number you're seeing is wildly lower than this you may have the
Turbo button or CPU speed set incorrectly, or have some kind of caching
problem [as described in Q6.9 `When I add more memory it slows to a
crawl.'.]

For values people have seen with other, rarer, chips, see the Bogomips
Information Sheet, published by Wim van Dorst <[email-masked]> in
comp.os.linux.announce.

-------------------------------------------------------------------------------

Question 6.7.  How do I set the timezone ?

Change directory to /usr/lib/zoneinfo; get the timezone package if you
don't have this directory.  The source can be found on sunsite.unc.edu in
/pub/Linux/system/Admin/timesrc-1.2.tar.gz.

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.

Don't try to use the TZ variable - leave it unset.

If you have a system which complies with a very recent version of the
Linux Filesystem Standard you will find that /usr/lib/zoneinfo/localtime
is a symbolic link to /etc/localtime.  In this case, simply copy the
appropriate file from /usr/lib/zoneinfo to /etc/localtime and leave the
link alone.  For example:
   cp /usr/lib/zoneinfo/US/Mountain /etc/localtime

-------------------------------------------------------------------------------

Question 6.8.  What version of Linux and what machine name am I using ?

Type:
   uname -a

-------------------------------------------------------------------------------

Question 6.9.  When I add more memory it slows to a crawl.

This is quite 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 RAMs have to be in certain sockets to be cached.

Sometimes you have to set jumpers to enable the caching.

Some motherboards don't cache all the RAM if you have more RAM per amount
of cache than they expect.  Usually a full 256K cache will solve this
problem.

If in doubt, check your motherboard manual.  If you still can't fix it
because the documentation is inadequate you might like to post a message
giving *all* the details - make, model number, date code, etc. so that
other Linux users can avoid it.

-------------------------------------------------------------------------------

Question 6.10.  Some programs (e.g. xdm) won't let me log in.

You are probably using non-shadow-password programs but are using shadow
passwords.

If so, you have to get or compile a shadow password version of the
program(s) in question.  The shadow password suite can be found in
(amongst other places):
   tsx-11.mit.edu:/pub/linux/sources/usr.bin/shadow-*
This is the source code; you will probably find the binaries in
.../linux/binaries/usr.bin.

-------------------------------------------------------------------------------

Question 6.11.  Some programs let me log in with no password.

You probably have the same problem as in Q6.10 `Some programs (e.g. xdm)
won't let me log in.', with an added wrinkle:

If you are using shadow passords you should put 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.

-------------------------------------------------------------------------------

Question 6.12.  My machine runs very slowly when I run GCC / X / ...

You probably don't have any swap enabled.  You need to enable swapping to
allow Linux to page out bits of data programs aren't using at the moment
to disk to make more room for other programs and data.  If you don't Linux
has to keep data in memory and throw away in-memory copies of programs
(which are paged straight from the filesystem) and so less and less
program is in memory and everything runs very slowly.

See the Installation HOWTO and the Installation and Getting Started Guide
[Q2.1 `Where can I get the HOWTOs and other documentation ?'] for details
of how to set up a swap partition or swapfile; see also Q4.5 `My swap area
isn't working.'.

Alternatively you may have too little real memory.  If you have less RAM
than all the programs you're running at once use Linux will use your hard
disk instead and thrash horribly.  The solution in this case is to not run
so many things at once or to buy more memory.  You can also reclaim some
memory by compiling and using a kernel with less options configured.  See
Q6.20 `How do I upgrade/recompile my kernel ?'.

You can tell how much memory and/or swap you're using by using the free
command, or by typing
    cat /proc/meminfo

-------------------------------------------------------------------------------

Question 6.13.  I can only log in as root.

You probably have some permission problems, or you have a file
/etc/nologin.

If the latter put rm -f /etc/nologin in your /etc/rc or /etc/rc.local.

Otherwise check the permissions on your shell, and any filenames which
appear in error messages, and also the directories containing these files
all the way back up the tree to the root directory.

-------------------------------------------------------------------------------

Question 6.14.  How can I produce core files ?

Since 0.99pl14 Linux has had corefiles turned off by default for all
processes.  You can turn them on by using the ulimit command in bash, or
the limit command in tcsh.  See the manpages or Q6.15 `How do I stop
producing core files ?' for more details.

After executing that command all programs run from that shell (directly or
indirectly) will be able to dump core.

If you wish to enable coredumping for all processes by default you can
change the default setting in <linux/sched.h> - see the definition of
INIT_TASK.

-------------------------------------------------------------------------------

Question 6.15.  How do I stop producing core files ?

If you use bash put
   ulimit -c 0
in your .shrc or .bashrc; if you use tcsh put
   limit coredumpsize 0
in your .cshrc.  For other shells check the shell's manpage.

This state of affairs is the default with newer kernels.

-------------------------------------------------------------------------------

Question 6.16.  My keyboard goes all funny after I switch VC's.

This is a bug in kernel versions before 0.99pl14-alpha-n.  Sometimes Linux
loses track of what modifier keys (Shift, Alt, Control etc.) are pressed
or not, and believes that one or more are pressed when they are not.  The
solution is to press and release each of the modifier keys (without
pressing any other keys) --- this will ensure that Linux knows what state
the keyboard is actually in.

This problem often occurs when switching out of X windows; it can
sometimes be avoided by releasing Ctrl and Alt very quickly after pressing
the F-key of the VC you are switching to.

-------------------------------------------------------------------------------

Question 6.17.  My screen is all full of weird characters instead of letters.

You probably sent some binary data to your screen by mistake.  Type echo
"^V^[c" (that's E C H O space control-V escape C return) to fix it.

-------------------------------------------------------------------------------

Question 6.18.  What is a .gz file ? And a .tgz ? And ... ?

.gz (and .z) files have been compressed using GNU gzip.  You have to get a
copy of gunzip (included in the gzip distribution and with most Linux
installations) to unpack the file.

.taz and .tz are tarfiles (made with Unix tar) compressed using standard
Unix compress.

.tgz (or .tpz) is a tarfile compressed with gzip.

The file command can often tell you what a file is.

If you find that gzip complains when you try to uncompress a gzipped file
you probably downloaded it in ASCII mode by mistake.  You must download
most things in binary mode - remember to type binary as a command in FTP
before using get to get the file.

-------------------------------------------------------------------------------

Question 6.19.  I have screwed up my system and can't log in to fix it.

Reboot from an emergency floppy, for example the Slackware a1 disk or the
MCC installation boot floppy.  Get to a shell prompt and mount your hard
disk with something like
   mount -t ext2 /dev/hda1 /mnt

Then your filesystem is available under the directory /mnt and you can fix
the problem.  Remember to unmount your hard disk before rebooting (cd back
down to / first or it will say it's busy).

-------------------------------------------------------------------------------

Question 6.20.  How do I upgrade/recompile my kernel ?

See the README which comes with the kernel release, in
        ftp.funet.fi:/pub/OS/Linux/PEOPLE/Linus
and mirrors thereof.  Try to get it from a closer site if possible;
ftp.funet.fi is a very busy site and therefore slow -- see Q2.3 `How do I
install Linux ?'.  You may already have a version of the kernel source
code installed on your system, but if you got it as part of a standard
distribution it is likely to be somewhat out of date (this is not a
problem if you only want a custom-configured kernel, but it probably is if
you need to upgrade.)

Remember that to make the new kernel boot you must run LILO after copying
the kernel into your root partition -- the Makefile in recent kernels has
a special zlilo target for this; try make zlilo.

-------------------------------------------------------------------------------

Question 6.21.  Can I have more than 3 serial ports by sharing interrupts ?

Not without some trickery.  This is a limitation of the ISA bus
architecture.

See the Serial HOWTO for information about how to work around this
problem.

-------------------------------------------------------------------------------

Question 6.22.  Emacs just dumps core.

You probably have the X version of Emacs that comes with SLS.  It doesn't
work without the X libraries.  The solution is to install X Windows or get
a newer Emacs binary without any X Windows support.

-------------------------------------------------------------------------------

Question 6.23.  How do I make a bootable floppy ?

Make a filesystem on it with bin, etc and lib directories -- everything
you need.  Install a kernel on it and arrange to have LILO boot it from
the floppy (see the LILO documentation, in lilo.u.*.ps).

If you build the kernel (or tell LILO to tell the kernel) to have a
ramdisk the same size as the floppy the ramdisk will be loaded at
boot-time and mounted as root in place of the floppy.

-------------------------------------------------------------------------------

Question 6.24.  How do I remap my keyboard to UK, French, etc. ?

For recent kernels, get kbd*.tar.gz from the same place as you got the
kernel source.  Make sure you get the appropriate version; you have to use
the right keyboard-mapping package to go with your kernel version.  The
latest at the time of writing is kbd-0.85.tar.gz, which works with at
kernel versions from 1.0.

For older kernels you have to edit the top-level kernel Makefile, in
/usr/src/linux.

You may find more helpful information in the Keyboard FAQ, on ftp.funet.fi
in /pub/OS/Linux/doc/kbd.FAQ.

-------------------------------------------------------------------------------

Question 6.25.  I've discovered a huge security hole in rm !

No you haven't.  You are obviously new to Unix and need to read a good
book on it to find out how things work.  Clue: ability to delete files
under Unix depends on permission to write the directory they are in.

-------------------------------------------------------------------------------

Question 6.26.  lpr and lpd aren't working.

Check the Printing HOWTO [Q2.1 `Where can I get the HOWTOs and other
documentation ?'].

-------------------------------------------------------------------------------

Question 6.27.  How do I make a shared library ?

Get tools-2.11.tar.gz from tsx-11.mit.edu, in /pub/linux/packages/GCC.
Read the documentation enclosed with these tools for instructions.

-------------------------------------------------------------------------------

Question 6.28.  What does VFS stand for ?

Virtual File System.  It's the abstraction layer between the user and real
filesystems like ext2, minix and msdos.  Amongst other things, its job is
to flush the read buffer when it detects a disk change on the floppy disk
drive:
   VFS: Disk change detected on device 2/0

This would seem like an appropriate entry for a glossary - Matt, are there
any plans to produce such a thing ?

===============================================================================

Section 7.  Frequently Encountered Error messages

 Q7.1        fdisk says Partition X has different phsyical/logical ...
 Q7.2        fdisk: Partition 1 does not start on cylinder boundary
 Q7.3        lp1 on fire
 Q7.4        INET: Warning: old style ioctl(IP_SET_DEV) called!
 Q7.5        ld: unrecognized option '-m486'
 Q7.6        GCC says Internal compiler error
 Q7.7        make says Error 139
 Q7.8        df says Cannot read table of mounted filesystems
 Q7.9        shell-init: permission denied when I log in.
 Q7.10       No utmp entry.  You must exec ... when I log in.
 Q7.11       EXT2-fs: warning: mounting unchecked filesystem
 Q7.12       EXT2-fs warning: maximal count reached
 Q7.13       EXT2-fs warning: checktime reached
 Q7.14       fdisk says cannot use nnn sectors of this partition
 Q7.15       fdisk says partition n has an odd number of sectors
 Q7.16       mtools says cannot initialise drive XYZ
 Q7.17       My AHA1542C doesn't work with Linux.

-------------------------------------------------------------------------------

Question 7.1.  fdisk says Partition X has different phsyical/logical ...

If the partition number (X, above) is 1 this is the same problem as Q7.2
`fdisk: Partition 1 does not start on cylinder boundary'.

If the partition begins or ends on a cylinder numbered beyond 1024, this
is because standard DOS disk geometry information format in the partition
table can't cope with cylinder numbers with more than 10 bits.

This will cause DOS to be unable to access the partition correctly, and
will make booting a Linux kernel from that partition using LILO
problematic at best.

You can still use the partition for Linux or other operating systems that
use linear addressing (ie, number the disk blocks sequentially without
looking at heads, tracks and sectors).

I'd recommend creating at least one Linux partition entirely under the
1024-cylinder limit and booting off that; the other partitions will then
be OK.

-------------------------------------------------------------------------------

Question 7.2.  fdisk: Partition 1 does not start on cylinder boundary

The version of fdisk that comes with many Linux systems creates partitions
that fail its own validity checking.  Unfortunately if you've already
installed your system there's not much you can do about this, apart from
copying the data off the partition, deleting and remaking it, and copying
the data back.

If you are creating a new partition 1 that starts in the first cylinder,
you can do the following to get a partition that fdisk likes.

1. Create partition 1 in the normal way.  A p listing will produce the
mismatch complaint.

2. Type u to set sector mode and do p again.  Copy down the number from
the "End" column.

3. Delete partition 1.

4. While still in sector mode recreate partition 1.  Set the first sector
to match the number of sectors per track.  This is the sector number in
the first line of the p output.  Set the last sector to the value noted in
2. above.

5. Type u to reset cylinder mode and continue with other partitions.

-------------------------------------------------------------------------------

Question 7.3.  lp1 on fire

This is a joke/traditional error message indicating that some sort of
error is being reported by your printer, but it isn't offline or out of
paper.  It may be that you have some kind of I/O or IRQ conflict - check
your cards' settings.  Hopefully it isn't really on fire ...

-------------------------------------------------------------------------------

Question 7.4.  INET: Warning: old style ioctl(IP_SET_DEV) called!

You are trying to use the old network configuration utilities; the new
ones can be found on tsx-11.mit.edu in
/pub/linux/packages/net/net-2/binaries.

Note that they cannot be used just like the old-style programs; see the
NET-2 HOWTO for instructions on how to set up networking correctly.

-------------------------------------------------------------------------------

Question 7.5.  ld: unrecognized option '-m486'

You have an old version of ld.  Install a newer binutils package -- this
will contain an updated ld:
   tsx-11.mit.edu:/pub/linux/packages/GCC/binutils.tar.z

-------------------------------------------------------------------------------

Question 7.6.  GCC says Internal compiler error

If the fault is repeatable (ie, it always happens at the same place in the
same file) you have discovered a bug in GCC.  See the GCC Info
documentation (type Control-h i in Emacs, and select GCC from the menu)
for details on how to report this -- make sure you have the latest version
though.

Note that this is probably not a Linux-specific problem; unless you were
compiling a program many other Linux users also compile you should not
post your bug report to any of the comp.os.linux groups.

If the problem is not repeatable you are very probably experiencing memory
corruption --- see Q7.7 `make says Error 139'.

-------------------------------------------------------------------------------

Question 7.7.  make says Error 139

Your compiler driver (gcc) dumped core.  You probably have a corrupted,
buggy or old version of GCC --- get the latest release.  Alternatively you
may be running out of swap space --- see Q6.12 `My machine runs very
slowly when I run GCC / X / ...' for more info.

If this doesn't fix the problem you are probably having problems with
memory or disk corruption.  Check that the clock rate, wait states and
refresh timing for your SIMMs are correct.  If so you may have some dodgy
SIMMs or a faulty hard disk or controller.

Linux, like any Unix, is a very good memory tester --- much better than
DOS-based memory test programs.

Reportedly some clone x87 maths coprocessors can cause problems; try
compiling a kernel with maths emulation [Q6.20 `How do I upgrade/recompile
my kernel ?']; you may need to use the no387 kernel command line flag on
the LILO prompt to force the kernel to use it, or it may be able to work
and still use the 387, with the maths emulation compiled in but mainly
unused.

-------------------------------------------------------------------------------

Question 7.8.  df says Cannot read table of mounted filesystems

There is probably something wrong with your /etc/mtab or /etc/fstab files.
If you have a reasonably new version of mount, /etc/mtab should be emptied
or deleted at boot time (in /etc/rc or /etc/rc.local), using something
like
   rm -f /etc/mtab*

Some versions of SLS have an entry for the root partition in /etc/mtab
made in /etc/rc by using rdev.  This is incorrect -- the newer versions of
mount do this automatically.

Other versions of SLS have a line in /etc/fstab that looks like:
    /dev/sdb1   /root   ext2   defaults
This is wrong.  /root should read simply /.

-------------------------------------------------------------------------------

Question 7.9.  shell-init: permission denied when I log in.

Your root directory and all the directories up to your home directory must
be readable and executable by everybody.  See the manpage for chmod or a
book on Unix for how to fix the problem.

-------------------------------------------------------------------------------

Question 7.10.  No utmp entry.  You must exec ... when I log in.

Your /etc/utmp is screwed up.  You should have
   > /etc/utmp
in your /etc/rc or /etc/rc.local.  See Q6.19 `I have screwed up my system
and can't log in to fix it.' for how to be able to do this.

-------------------------------------------------------------------------------

Question 7.11.  EXT2-fs: warning: mounting unchecked filesystem

You need to run e2fsck (or fsck -t ext2 if you have the fsutils package)
with the -a option to get it to clear the `dirty' flag, and then cleanly
unmount the partition during each shutdown.

The easiest way to do this is to get the bootutils package, available on
sunsite and tsx-11.  You have to make sure you have a recent umount
command.

NB don't try to check a filesystem that's mounted read-write - this
includes the root partition if you don't see
   VFS: mounted root ... read-only
at boot time.  You must arrange for to initially mount the root filesystem
readonly, check it if necessary, and then remount it read-write.  Read the
documentation that comes with bootutils to find out how to do this.

Note that you need to specify the -n option to mount to get it not to try
to update /etc/mtab, since the root filesystem is still read-only and this
will otherwise cause it to fail !

-------------------------------------------------------------------------------

Question 7.12.  EXT2-fs warning: maximal count reached

This message is issued by the kernel when it mounts a filesystem that's
marked as clean, but whose `number of mounts since check' counter has
reached the predifined value.  The solution is to get the latest version
of the ext2fs utilities (e2fsprogs-0.4a.tar.gz at the time of writing)
from the usual sites [Q2.4 `Where can I get Linux material by FTP ?'].

The maximal number of mounts value can be examined and changed using the
tune2fs program from this package.

-------------------------------------------------------------------------------

Question 7.13.  EXT2-fs warning: checktime reached

Kernels from 1.0 onwards support checking a filesystem based on the
elapsed time since the last check as well as by the number of mounts.  Get
the latest version of the ext2fs utilities [see Q7.12 `EXT2-fs warning:
maximal count reached'].

-------------------------------------------------------------------------------

Question 7.14.  fdisk says cannot use nnn sectors of this partition

Originally Linux only supported the Minix filesystem, which cannot use
more than 64Mb per parition.  This limitation is not present in the more
advanced filesystems now available, such as ext2fs (the 2nd version of the
Extended Filesystem) and xiafs (Qi Xia's filesystem).

If you intend to use ext2fs or xiafs you can ignore the message.

-------------------------------------------------------------------------------

Question 7.15.  fdisk says partition n has an odd number of sectors

The PC disk partitioning scheme works in 512-byte sectors, but Linux uses
1K blocks.  If you have a partition with an odd number of sectors the last
sector is wasted.  Ignore the message.

-------------------------------------------------------------------------------

Question 7.16.  mtools says cannot initialise drive XYZ

This means that mtools is having trouble accessing the drive.  This can be
due to several things.

Often this is due to the permissions on floppy drive devices (/dev/fd0*
and /dev/fd1*) being incorrect --- the user running mtools must have the
appropriate access.  See the manpage for chmod for details.

Most versions of mtools distributed with Linux systems (not the standard
GNU version) use the contents of a file /etc/mtools to discover which
devices and densities to use, in place of having this information compiled
into the binary.  Mistakes in this file often cause problems.  There is
often no documentation about this --- distribution packagers please note
that this is *evil*.

For the easiest way to access your DOS files (especially those on a hard
disk partition) see Q3.2 `How do I access files on my DOS partition or
floppy ?'.  Note - you should never use mtools to access files on an
msdosfs mounted partition or disk !

-------------------------------------------------------------------------------

Question 7.17.  My AHA1542C doesn't work with Linux.

You need to turn off most of the "advanced BIOS" options - all but the one
about scanning the bus for bootable devices.  The option to allow disks
with more than 1024 cylinders is only required as a workaround for a DOS
misfeature and should be turned *off* under Linux.

===============================================================================

Section 8.  The X Window System

 Q8.1        Does Linux support X Windows ?
 Q8.2        Where can I get an Xconfig for my video card and monitor ?
 Q8.3        xterm logins show up strangely in who, finger
 Q8.4        I can't get X Windows to work right.

-------------------------------------------------------------------------------

Question 8.1.  Does Linux support X Windows ?

Yes.  Linux uses XFree86 2.0, which is a derivative of X11R5.  You need to
have a video card which is supported by XFree86 2.0.  See the Linux
XFree86 HOWTO for more details.

Some of the Linux releases -- MCC, for example -- don't come with X
Windows already included; however you can easily download and install it
from /pub/Linux/X11/Xfree86-2.0 on sunsite.unc.edu and its mirror sites.
Read the XFree86 HOWTO for installation instructions.

Other releases -- Slackware, Debian, TAMU and SLS, for example -- come
with X Windows already included

-------------------------------------------------------------------------------

Question 8.2.  Where can I get an Xconfig for my video card and monitor ?

See the Linux XFree86 HOWTO.

You'll need to put together your own Xconfig file, because it depends on
the exact combination of video card and monitor you have.  It's not that
hard to do -- read the instructions that came with XFree86-2.0, in
/usr/X386/lib/X11/etc.  The file you probably most need to look at is
README.Config.

Please don't post to comp.os.linux.help asking for an Xconfig.

-------------------------------------------------------------------------------

Question 8.3.  xterm logins show up strangely in who, finger

The xterm that comes with XFree86 2.0 and earlier doesn't correctly
understand the format that Linux uses for the /etc/utmp file, where the
system records who is logged in.  It therefore doesn't set all the
information correctly.

I do not know whether XFree86 2.1 fixes this problem.

-------------------------------------------------------------------------------

Question 8.4.  I can't get X Windows to work right.

Read the XFree86 HOWTO - note the question and answer section.

Try reading to comp.windows.x.i386unix -- specifically read the the FAQ
for that group.

Please don't post X Windows or XFree86 related questions to
comp.os.linux.help unless they are Linux-specific.

===============================================================================

Section 9.  How to get further assistance

 Q9.1        You still haven't answered my question !
 Q9.2        What to put in a posting to comp.os.linux.help

-------------------------------------------------------------------------------

Question 9.1.  You still haven't answered my question !

Please read all of this answer before posting.  I know it's a bit long,
but you may be about to make a fool of yourself in front of 50000 people
and waste hundreds of hours of their time.  Don't you think it's worth it
to spend some of your time reading and following these instructions ?

If you think an answer is incomplete or inaccurate, please mail Ian
Jackson at <[email-masked]>.

Read the appropriate Linux Documentation Project books - see Q2.1 `Where
can I get the HOWTOs and other documentation ?'.

If you're a Unix newbie read the FAQ for comp.unix.questions, and those
for any of the other comp.unix.* groups that may be relevant.

Linux is a Unix clone, so almost everything you read there will apply to
Linux.  Those FAQs can, like all FAQs, be found on rtfm.mit.edu in
/pub/usenet/news.answers (the [email-masked] can send you these
files, for those who don't have FTP access).

Check the relevant HOWTO for the subject in question, if there is one, or
an appropriate old-style sub-FAQ document.  Check the FTP sites.

Try experimenting --- that's the best way to get to know Unix and Linux.

Read the documentation.  Check the manpages (type man man if you don't
know about manpages.  Try man -k <subject> --- it often lists useful and
relevant manpages.

Check the Info documentation (type C-h i, i.e. Control H followed by I in
Emacs) --- NB this isn't just for Emacs; for example the GCC documentation
lives here as well.

There will also often be a README file with a package giving installation
and/or usage instructions.

Make sure that you don't have a corrupted or out-of-date copy of the
program in question.  If possible, download it again and reinstall it ---
perhaps you made a mistake the first time.

Read comp.os.linux.announce --- this often contains very important
information for all Linux users.

X-Windows questions belong in comp.windows.x.i386unix, not in
comp.os.linux.help.  But read the group first (including the FAQ), before
you post !

Only if you have done all of these things and are still stuck should you
post to comp.os.linux.help; alternatively you could send email to
[email-masked].  Make sure you read the next question, Q9.2
`What to put in a posting to comp.os.linux.help', first.

-------------------------------------------------------------------------------

Question 9.2.  What to put in a posting to comp.os.linux.help

Please read carefully the following advice about how to write your
posting.  Taking heed of it will greatly increase the chances that an
expert and/or fellow user reading your posting will have enough
information and motivation to reply.

Make sure you give full details of the problem, including

* What program, exactly, you are having problems with.  Include the
  version number if known and say where you got it.  Many standard
  commands tell you their version number if you give them a --version
  option.

* Which Linux release you're using (MCC, Slackware, whatever) and what
  version of that release.

* The *exact* and *complete* text of any error messages printed.

* Exactly what behaviour you were expecting, and exactly what behaviour
  you observed.  A transcript of an example session is a good way of
  showing this.

* The contents of any configuration files used by the program in question
  and any related programs.

* What version of the kernel and of the shared libraries you are using.
  The kernel version can be found by typing uname -a, and the shared
  library version by typing ls -l /lib/libc.so.4.

* Details of what hardware you're running on, if it seems appropriate.

You are in little danger of making your posting too long unless you
include large chunks of source code or uuencoded files, so err on the side
of giving too much information.

Use a clear, detailed Subject line.  Don't put things like `doesn't work',
`Linux', `help' or `question' in it --- we already knew that ! Save the
space for the name of the program, a fragment of the error message,
summary of the unusual behaviour, etc.

If you are reporting an `unable to handle kernel paging request' message,
follow the instructions in the Linux kernel sources README for turning the
numbers into something more meaningful.  If you don't do this noone who
reads your post will be able to do it for you, as the mapping from numbers
to function names varies from one kernel to another.

Put a summary paragraph at the top of your posting.

At the bottom of your posting, ask for responses by email and say you'll
post a summary.  Back this up by using Followup-To: poster.  Then, do
actually post a summary in a few days or a week or so.  Don't just
concatenate the replies you got --- summarise.  Putting the word SUMMARY
in your summary's Subject line is also a good idea.

Make sure your posting doesn't have an inappropriate References header
line.  This marks your article as part of the thread of the article
referred to, which will often cause it to be junked by the readers with
the rest of a boring thread.  If you use (t)rn you must make sure that
when you post you use the lowercase f key; using uppercase F and deleting
the quoted text doesn't do the same thing.  However Some versions of trn
2.x have a bug which produces this effect effen if you use f.  If this
applies to your version you can edit out the References line in the
message before you post, or just use plain Pnews to make a new posting.
You should always read the header before posting anyway.

You might like to say in your posting that you've read this FAQ and the
appropriate HOWTOs - this may make people less likely to skip your
posting.

Remember that you should not post email sent to you personally without the
sender's permission.

===============================================================================

Section 10.  Administrative information and acknowledgements

 Q10.1       Feedback is invited
 Q10.2       Formats in which this FAQ is available
 Q10.3       Authorship and acknowledgements
 Q10.4       Disclaimer and Copyright

-------------------------------------------------------------------------------

Question 10.1.  Feedback is invited

Please send me your comments on this FAQ.

I accept submissions for the FAQ in any format;  All contributions
comments and corrections are gratefully received.

Please send them to <[email-masked]>.

-------------------------------------------------------------------------------

Question 10.2.  Formats in which this FAQ is available

This document is available as ASCII text, an Emacs Info document and
PostScript.

The ASCII and Emacs Info versions and a Lout typesetter file (from which
the PostScript is produced) are generated automatically by a Perl script
which takes as input a file in the Bizarre Format with No Name.

The output files linux-faq.ascii, .info and .ps and a tarfile
linux-faq.source.tar.gz, containing the BFNN source and Perl script
converter, are available in the docs directories of the major Linux FTP
sites.

-------------------------------------------------------------------------------

Question 10.3.  Authorship and acknowledgements

This FAQ was compiled by Ian Jackson <[email-masked]>, with
assistance and comments from others too numerous to mention.  It was
loosely based on the original Linux FAQ by Marc-Michel Corsini.

Special thanks are due to Matt Welsh, who coordinates the HOWTOs and has
written substantial portions of many of them, and to Marc-Michel Corsini.
Thanks also to the contributors to the previous Linux FAQ, and to those
sent me comments about this FAQ, and who answered questions on the
newsgroup.

Last but not least, thanks to Linus Torvalds and the other contributors to
Linux for giving us something to write about !

-------------------------------------------------------------------------------

Question 10.4.  Disclaimer and Copyright

Note that this document is provided as is.  The information in it is *not*
warranted to be correct; you use it at your own risk.

Following recent reports on the faq-maintainers list I think it wise to
change the copyright again:

Linux Frequently Asked Questions with Answers is Copyright 1994 by Ian
Jackson <[email-masked]>.  It may be reproduced and distributed in
whole or in part, subject to the following conditions:

* This copyright and permission notice and the paragraph in the
  introduction about the frequency of updates must be retained on all
  complete or partial copies.

* Any translation or derivative work must be approved by me before
  distribution.  Email me - I'll probably be happy to oblige !

* If you wish to charge for non-machine-readable copies you need my
  approval before distribution.  Note that this restriction is not
  intended to prohibit charging for the service of printing or copying a
  document supplied by your customer.

* If you distribute Linux Frequently Asked Questions with Answers in part,
  instructions for obtaining the complete version must be included, and a
  means for obtaining a complete version free or at cost price provided.

Exceptions to these rules may be granted, and I shall be happy to answer
any questions about this copyright --- write to Ian Jackson, Churchill
College, Cambridge, CB3 0DS, United Kingdom or email
[email-masked].  These restrictions are here to protect the
contributors, not to restrict you as educators and learners.

===============================================================================
-- 
Ian Jackson, at home  <[email-masked]> or <[email-masked]>
PGP2 public key available on server.  Urgent email: <[email-masked]>
2 Lexington Close, Cambridge, CB4 3LS, England;  phone: +44 223 64238