% Linux Installation and Getting Started    -*- TeX -*-
% booting.tex
% Copyright (c) 1992-1994 by Matt Welsh <mdw@sunsite.unc.edu>
%
% This file is freely redistributable, but you must preserve this copyright 
% notice on all copies, and it must be distributed only as part of "Linux 
% Installation and Getting Started". This file's use is covered by the 
% copyright for the entire document, in the file "copyright.tex".

\subsection{Problems with booting the installation media}
\namedlabel{sec-install-probs-booting}{Problems with booting the installation media}

\index{installation!problems!booting|(}
\index{booting!problems|(}

When attempting to boot the installation media for the first time, you
may encounter a number of problems. These are listed below.
Note that the following problems are {\em not\/} related to booting your 
newly-installed Linux system. See 
Section~\ref{sec-install-probs-postinstall} 
for information on these kinds of pitfalls.

\begin{itemize}
\item {\bf Floppy or media error when attempting to boot.}

The most popular
cause for this kind of problem is a corrupt boot floppy. Either the
floppy is physically damaged, in which case you should re-create the
disk with a {\em brand new\/} floppy, or the data on the floppy is bad,
in which case you should verify that you downloaded and transferred the
data to the floppy correctly. In many cases, simply re-creating the boot
floppy will solve your problems. Retrace your steps and try again.

If you received your boot floppy from a mail order vendor or some other
distributor, instead of downloading and creating it yourself, contact the
distributor and ask for a new boot floppy---but only after verifying that
this is indeed the problem. 

\item {\bf System ``hangs'' during boot or after booting.} 

After the installation
media boots, you will see a number of messages from the kernel itself, 
indicating which devices were detected and configured. After this, you will
usually be presented with a login prompt, allowing you to proceed with
installation (some distributions instead drop you right into an installation
program of some kind). The system may appear to ``hang'' during several of
these steps. During all of these steps, be patient; loading
software from floppy is very slow. In many cases, the system has not
hung at all, but is merely taking a long time. Verify that there is no
drive or system activity for at least several minutes before assuming that 
the system is hung. 
\begin{enumerate}
\index{LILO!problems booting}
\item After booting from the {\tt LILO} prompt, the system must load the
kernel image from floppy. This may take several seconds; you will know
that things are going well if the floppy drive light is still on.

\item While the kernel boots, SCSI devices must be probed for. If you do
not have any SCSI devices installed, the system will ``hang'' for up to 15
seconds while the SCSI probe continues; this usually occurs after the line
\begin{tscreen}
lp\_init: lp1 exists (0), using polling driver
\end{tscreen}
appears on your screen.

\item After the kernel is finished booting, control is transferred to the
system bootup files on the floppy. Finally, you will be presented with
a login prompt, or be dropped into an installation program. If you are
presented with a login prompt such as
\begin{tscreen}
Linux login:
\end{tscreen}
you should then login (usually as {\tt root} or {\tt install}---this varies
with each distribution). After entering the username, the system may 
pause for 20 seconds or more while the installation program or shell is
being loaded from floppy. Again, the floppy drive light should be on. 
Don't assume that the system is hung.

\end{enumerate}

Any of the above items may be the source of your problem. However, 
it is possible that
the system actually may ``hang'' while booting, which can be due
to several causes. First of all, you may not have enough available RAM
to boot the installation media. (See the following item for information
on disabling the ramdisk to free up memory.)

The cause of many system hangs is hardware incompatibility. 
Section~\ref{sec-intro-hardware} in the last chapter presented an 
overview of
supported hardware under Linux. Even if your hardware is supported, you may
run into problems with incompatible hardware configurations which
are causing the system to hang. See 
Section~\ref{sec-install-probs-hardware}, below, for a discussion of 
hardware incompatibilities.


\item {\bf System reports out of memory errors while attempting to
boot or install the software.} 

This item
deals with the amount of RAM that you have available. On systems
with 4 megabytes of RAM or less, you may run into trouble booting the
installation media or installing the software itself. This is because
many distributions use a ``ramdisk'', which is a filesystem loaded 
directly into RAM, for operations while using the installation media.
The entire image of the installation boot floppy, for example, may be
loaded into a ramdisk, which may require more than a megabyte of RAM.

The solution to this problem is to disable the ramdisk option when
booting the install media. Each release has a different procedure for
doing this; on the SLS release, for example, you type ``{\tt floppy}''
at the LILO prompt when booting the {\tt a1} disk. 
See your distribution's documentation for details.

You may not see an ``out of memory'' error when attempting to boot or install
the software; instead, the system may unexpectedly hang, or 
fail to boot. If your system hangs, and none of the
explanations in the previous section seem to be the cause, try disabling
the ramdisk.

Keep in mind that Linux itself requires at least 2 megabytes of RAM to
run at all; some distributions of Linux require 4 megabytes or more. 

\item {\bf The system reports an error such as ``{\tt permission denied}''
or ``{\tt file not found}'' while booting.}

This is an indication that your installation bootup media is corrupt. If you
attempt to boot from the installation media (and you're sure that you're
doing everything correctly), you should not see any errors such as this. 
Contact the distributor of your Linux software and find out about the problem,
and perhaps obtain another copy of the boot media if necessary. If you 
downloaded the bootup disk yourself, try re-creating the bootup disk, and
see if this solves your problem.

\item {\bf The system reports the error 
``{\tt VFS: Unable to mount root}'' when booting.}

This error message means that the root filesystem (found on the boot 
media itself), could not be found. This means that either your boot
media is corrupt in some way, or that you are
not booting the system correctly. 

For example, many CD-ROM distributions require that you have the CD-ROM 
in the drive when booting. Also be sure that the CD-ROM drive is on, and 
check for any activity. It's also possible that the system is not locating 
your CD-ROM drive at boot time; see 
Section~\ref{sec-install-probs-hardware} for more information.

If you're sure that you are booting the system correctly, then your 
bootup media may indeed be corrupt. This is a very uncommon problem, so 
try other solutions before attempting to use another boot floppy or tape.

\end{itemize}

\index{installation!problems!booting|)}
\index{booting!problems|)}
