When building bootdisks, the first few tries often will not boot. The general approach to building a root disk is to assemble components from your existing system, and try and get the diskette-based system to the point where it displays messages on the console. Once it starts talking to you, the battle is half over because you can see what it is complaining about, and you can fix individual problems until the system works smoothly. If the system just hangs with no explanation, finding the cause can be difficult. To get a system to boot to the stage where it will talk to you requires several components to be present and correctly configured. The recommended procedure for investigating the problem where the system will not talk to you is as follows:
/bin on your
root diskette.
/lib directory on your hard disk.
/dev directory in your
existing system also exist on your root diskette filesystem, where those links
are to devices which you have included in your root diskette. In particular,
/dev/console links are essential in many cases.
/dev/tty1, /dev/null, /dev/zero,
/dev/mem, /dev/ram and /dev/kmem files.
Once these general aspects have been covered, here are some more specific files to check:
init is included as /sbin/init or
/bin/init. Make sure it is executable.
ldd init to check init's libraries. Usually this is just
libc.so, but check anyway. Make sure you included the necessary
libraries and loaders.
ld.so for a.out or ld-linux.so for ELF.
getty (or some getty-like program, such as
agetty, mgetty or
getty_ps).
Double-check these against
your hard disk inittab. Check the man pages of the program you use to
make sure these make sense. inittab is possibly the trickiest part
because its syntax and content depend on the init program used and the
nature of the system. The only way to tackle it is to read the man pages
for init and inittab and work out exactly what your existing
system is doing when it boots. Check to make sure
/etc/inittab has a system initialisation entry. This should
contain a command to execute the system initialization script, which must
exist.
init, run ldd on your getty to see
what it needs, and make sure the necessary library files and loaders were
included in your root filesystem.
bash or ash)
capable of running all of your rc scripts.
If init starts, but you get a message like:
Id xxx respawning too fast: disabled for 5 minutes
it is coming from init, usually indicating that getty or
login is dying as soon as it starts up.
Check the getty and login
executables and the libraries they depend upon. Make sure the invocations
in /etc/inittab are correct. If you get strange messages from
getty, it may mean the calling form in /etc/inittab is
wrong. The options of the getty programs are variable; even different
versions of agetty are reported to have different incompatible calling
forms.
If you try to run some executable, such as df, which is on your rescue
disk but you yields a message like: df: not found, check two things: (1)
Make sure the directory containing the binary is in your PATH, and (2) make
sure you have libraries (and loaders) the program needs.