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[linux_from_scratch_hints.git] / OLD / one-partition-hint.txt

TITLE:          One Partition HINT
LFS VERSION:    2.x-4.0*
AUTHOR:         Alex Kloss (LX) <l.x.@gmx.de>

SYNOPSIS:
        Install LinuxFromScratch using only 1 bootable Linux-partition
        on which is your actual distribution.

HINT:
________________________________________________________________________________

The following text describes the changes you have to make to the normal LFS 
installing procedere when using only 1 bootable partition. It's not complete
without the LFS Book. It is just a description of the things you ought to do
in a different way than declared in the LFS book. It splits up into 2 parts
that differ from the Book: first, of course, the making of partition, which is
replaced by the making and setup of a loop device file, and next, the deletion
of the previous system due to the need of diskspace for the new one and the
installation and boot setup, that differs a bit, too.
________________________________________________________________________________

*: A certain Version of LFS is not really necessary. You can perform the 
   following tricks with any recent LFS Version known to me. The only thing 
   that really depends on the LFS version are the Chapter Names and Numbers.
________________________________________________________________________________

HISTORY:

Summer 2000: After doing this little trick on my own notebook, I urged
myself to write a hint (after all, I had a lot fun with LFS and wanted to 
help spread that fun).

Somewhen later 2000: While using my own hint when I tried to make a LFS BootCD 
without using the hint (I'll never do that again), I stumbled over a nice 
information about losetup, which opens a better way to handle loop devices and
added it to that hint.

14. Dec. 2001: After a few month, I wanted 1. to do a new LFS using my hint 
again (not only for the fun of it, I also wanted the System as new as possible),
2. try to reorganise this hint and 3. make the scripts on the end a bit nicer.
Note: I had to enlarge the lfs.disk file a bit, due to the fact that on some 
systems, during glibc compilation in chapter 6 the disk usage conquers 800MB.

19. Dec. 2001: Corrected a bad typo

30. Mar. 2002: I'm trying to keep this hint up to date, so another 
installation is about to take place. I want to go a bit beyond the current 
version, so I'll try to use gcc-3.0.4 and another few versions not yet used by
the book. Wish me luck!

31. Oct. 2002: Currently testing LFS 4.0 on a One Partition Build. Since
the chapters have a new structure and the static utils are stored in a
separate directory, the advantages should be used in this hint, too.

________________________________________________________________________________

THANKS:
Many thanks goes to Gerard, without his book, developing this hint had never 
been possible.
Thanks to the whole bunch of people that usually idles the whole day on 
#lfs@irc.linuxfromscratch.org for helping me in so many ways.
And thanks to all the people not mentioned here for not minding it...
________________________________________________________________________________

REISERFS WARNING:

If you're using reiserfs, this hint is almost unusable for you due to
deletion errors on a recursive mounted volume with reiserfs (the files
will be deleted, but the space wouldn't be freed). You could still use
the hint to make everything ready for a transfer using a bootdisk/CD,
but don't try the "Delete the previous System" section or further.
You've been warned!

RECOMMENDATION:

Make yourself a bootdisk or bootCD, whatever is sufficient on your
system. You can prevent a lot of damage to your system. 

If you don't know how to make a bootdisk or bootCD, look at the hints,
the BLFS section about it or search for bootdisk on freshmeat. Be sure
that the bootdisk/CD is able to read/write your root partition, e.g. a
tomsrtbt is currently not able to mount reiserfs.

INSTALLATION:

When you come to the part of the LFS Book which is called:

Part II, Paragraph 4
====================

Preparing a new partition

You don't want to create a new partition! That's why you're trying to use this 
hint. Therefore, this should be replaced with:

Making a loop device file and setting it up

Be sure to be superuser and that you have all variables ($LFS) set up like
you're told in the book. Then make a file containing enough MB of
nothing using:

        dd if=/dev/zero of=/tmp/lfs.disk bs=1M count=XXX

This file /tmp/lfs.disk will become our loop device file afterwards. The newer
versions of software you use, the more space you need for compiling; you might
want to replace XXX with 800 for LFS 2.x, 900-1000 for LFS 3.x and
1100-1300 for LFS 4.x or even more to be on the safe site.

LFS 4.0 allows to put all the static stuff to another directory, so it
would be cool to part the loopback volumes, too:

        dd if=/dev/zero of=/tmp/lfs.disk bs=1M count=450 &&
        dd if=/dev/zero of=/tmp/static.disk bs=1M count=750

This makes one volume for the finished LFS and one for the static stuff
you'll delete afterwards.

________________________________________________________________________________

Command explanations

dd: 

data dump utility - a small utility to read from an input file/device and dump 
the data into an output file.

if=/dev/zero: 

defining /dev/zero as Input file. We don't need nor want any input. The Zero 
device contains as much "0" as we want to read from it.

of=/tmp/lfs.disk: 

we dump a choosed amount full of nothing into the Output File called
"lfs.disk" in the directory /tmp. It's not necessary to call it like
that. You can even put it into any directory you got read/write-rights
for. But if you call it otherwise, you'll better remind to change this
filename within the later instructions.

bs=1M: 

Blocksize is set to 1 MegaByte.

count=XXX: 

We want XXX blocks each containing 1MB, so our file will be XXX MB big.
Version 2.x can be build with about 800MB, Version 3.x with about 1GB,
Version 4.x with about 1.2GB. If you want to be on the safe site, you
might want to take 100MB more. Even if it the size written in the
book works, when installing glibc, you may reach the limits faster than
you thought.
________________________________________________________________________________

Finding out wether the loop device is available and install it if not

For this hint, you need the loop device to be installed in your kernel,
either as module or included. To find out wether it is available, simply
try

        dmesg | grep loop

if you get something like 

        loop: loaded (max 8 devices)
        Calibrating delay loop... XXXX.XX BogoMIPS

The driver is already loaded. If you don't get it, try

        modprobe loop

If modprobe complains about the module not to be found, it's possible,
that you haven't compiled it into your kernel. If not, you can skip the
following section.
________________________________________________________________________________

Command Explanation

dmesg:

Giving the kernel messages (like these you see every bootup - if you
ever see one, actually) to the standard output.

|:

A so-called "pipe". Gives the standard output from one command to the
standard input of another one.

grep loop:

print only the lines with "loop" in it, e.g. the one about the loop
device driver.
________________________________________________________________________________

Setting up the loop device in your kernel

First, we check again, if there's really no loop device support in your kernel
(there are few chances that depmod didn't run properly or that you're running
the wrong kernel):

        cat /usr/src/linux/.config | grep CONFIG_BLK_DEV_LOOP

If you get something like

CONFIG_BLK_DEV_LOOP=Y 

meaning the support is compiled into the kernel, or

CONFIG_BLK_DEV_LOOP=M

stating that loop device support is compiled as module.
If you get something like

#CONFIG_BLK_DEV_LOOP is not set

you could change the necessary option by typing (or copy and paste - X
is great!)

        sed s/\#\ CONFIG_BLK_DEV_LOOP\ is\ not\ set/CONFIG_BLK_DEV_LOOP=m/ \
        /usr/src/linux/.config > conf && mv conf /usr/src/linux/.config &&
        cd /usr/src/linux && make modules modules_install && insmod loop

After some minutes (depending on the speed of your system) you should be
able to use the loop device.
________________________________________________________________________________

Command Explanation:

cat /usr/src/linux/.config: 

writes the kernel configuration to the standard output.

| grep CONFIG_BLK_DEV_LOOP: 

searches the output for the loop-device-option.

sed...: 

replaces the "is not set" instruction with the instruction for making a module
to use the loop device. For further explanation, please read the LFS book.

insmod loop: 

loading the module for mounting loop devices

mount lfs.disk /mnt/lfs -o loop: 

mounting the disk image file to the directory /mnt/lfs using the loop device 
driver (-o loop).
________________________________________________________________________________

If your loop device was already available, you should get on with things
right here:

Setting up the loop device

You load the file you made to the loop device with the command

        losetup /dev/loop0 /tmp/lfs.disk

And if you're using LFS 4.x with splitting of lfs and static, add

        losetup /dev/loop1 /tmp/static.disk

If you get an error: /dev/loop0 device file not found, it so seems that
you're missing the device file (which is really unusual), but you could
make it easily by typing

        mknod b 7 0 /dev/loop0

And for the splitting again

        mknod b 7 1 /dev/loop1

and perform the losetup again.
________________________________________________________________________________

Command Explanations

losetup /dev/loop0 /tmp/lfs.disk:

Attaching the file /tmp/lfs.disk to the loop device on /dev/loop0. This
is somewhat like mounting, only there's no filesystem on a device to
mount to a directory, but a file that gets "mounted" to a device for
later mounting.

mknod b 7 0 /dev/loop0:

Making a block device with major/minor nr. 7/0 using the filename
/dev/loop0. You could read the mknod manpage and the devices.txt of
the kernel Documentation for further informations on the issue.
________________________________________________________________________________

Creating a ext2 file system on the new partition

We don't have a new partition. But we have our file "lfs.disk" (or whatever you 
called it). on the /dev/loop0 device So instead of creating the file system 
on /dev/hda2 or any other partition, we're using the command on the
loop device our file is attached to:
 
        mke2fs /dev/loop0

And if you made a static.disk you should also

        mke2fs /dev/loop1

You could also use mkreiserfs or any other filesystem that's capable of
unix-style attributes, but I should warn you that e.g. reiserfs produces
grossiping amounts of overhead, so prepare yourself in patience for a
slow installation. I hear your questions why reiserfs should be slower
than ext2fs at a loop device. This is because the reiserfs uses a
journal which is accessed every time at write accesses, so you have to
write almost any data twice vs. once using ext2fs.

If you haven't got any idea about what I was writing about the last
paragraph, just believe me using ext2fs is the best method.
________________________________________________________________________________

Command explanations

mke2fs /dev/loop0: 

creating an ext2 file system through /dev/loop0 into the file lfs.disk
instead of an block device 
(like e.g. /dev/hda1).
________________________________________________________________________________

Mounting the new partition

        mount /dev/loop0 /mnt/lfs

And again the static part:

        mkdir /mnt/lfs/static
        mount /dev/loop1 /mnt/lfs/static
________________________________________________________________________________

Command explanations

You don't really expect me to explain commands like that, hm?
________________________________________________________________________________

Where to put the sources
========================

When using this hint, you're possibly about to have space problems. You
can reduce such by putting the sources to your usual partitions, using
an extra terminal to extract the source package you intend to compile
and apply the patches by using the following commands

        cd /mnt/lfs/<sourcedir>/<packagedir> &&
        bzcat <patch> | patch -Np1

Of course you can delete every packagedir after installation.


Halting the Building of LFS
===========================

So you found that building LFS using this hint takes too long to do it
in one pass? Never mind. All you have to do is save the system in a
secure state so you can shut down safely. When in chroot'ed mode, first

        umount /proc

Then exit the chrooted mode. If you got a static volume, you sure want
to

        umount /mnt/lfs/static

before you

        umount /mnt/lfs

Now you can set back the loop devices:

        losetup -d /dev/loop0

and for the static part

        losetup -d /dev/loop1

Now you can safely shut down your system. When you start again, you need
to perform those steps "backwards", like you already did in the
beginning:

        losetup lfs.disk /dev/loop0
        losetup static.disk /dev/loop1
        mount /dev/loop0 /mnt/lfs
        mount /dev/loop1 /mnt/lfs/static

chroot and mount proc if necessary (use the commands you find in the LFS
Book, they may differ from version to version). Omit the "/dev/loop1"
stuff (every 2nd line) if you've not using a static volume.

________________________________________________________________________________


Go on with LFS
============== 

The following steps are quite the same. The only differences starts again when 
you want to make this drive bootable:

Part II, Chapter 8
==================

Making the LFS System bootable.

A thought on making the kernel in LFS: why reconfigure everything? Even
if you've got an old kernel, most of the things you've chosen (or not)
during kernel configuration have not changed a bit. You could fasten up
this if instead of

        make menuconfig

using out of the chroot'ed environment

        cp /usr/src/linux/.config $LFS/usr/src/linux
        <enter chroot>
        make oldconfig

Now you only get asked on the things that weren't configured with your
new kernel (which should be somewhat less work than choosing every
menu). If you're unsure, you could still check it with "make menuconfig".

Make your kernel and /etc/lilo.conf in the chroot'ed environment as described 
in the LFS book. Don't try to start lilo now! Stop here! I hope you're
still in the chroot'ed environment, otherwise go back there.

The only bootable partition you've got is the one your current distro is 
running on. 

If you want to use the /tmp/lfs.disk file for anything else than
installing LFS over your distribution, you'll probably not need the
following part.

You're about to install LFS on the partition, deleting the distro. But
before you get started, read the following warning carefully:

--------------------------------------------------------------------------------
                Do yourself a real big favour and get a bootdisk! 
--------------------------------------------------------------------------------

If you delete your distribution and have a power failure, you would lose
your whole system (including the lfs.disk file that you can't access
anymore without a bootable linux system).
________________________________________________________________________________

Mounting the main partition

Mount the main partition to "/mnt" in the chroot'ed environment suggesting your 
main partition is /dev/hda1, otherwise fill in what is necessary:

        mount /dev/hda1 /mnt

Explanations of the command shouldn't be necessary. Just to help your 
imagination. The main partition is now mounted to a directory in a file 
attached to a block device which is mounted on the main partition (that is 
mounted to a directory...). This is a nice example for recursion. And this 
could get another nice example of an almost infinite loop (depending on your 
harddisk's size), if you try to copy everything to mount. Or an destructive 
loop, if you try to delete everything in /mnt (because this also holds the 
file currently working as your root environment). If you're asking what I'm
talking about, never mind, just follow the next instructions very carefully.
________________________________________________________________________________

Making sure init finds his getty

If you're not completely puzzled about that headline, you could go
straight to the following paragraph. "init" is the process that is
started by the kernel to start everything else during the bootup.
Everything else, that is, all calls that are in /etc/inittab. In this
inittab, you should find some version program getty, for example agetty
or mgetty, but maybe only getty. This program is used to load the
programs that allow you to login into your system. Now imagine you
delete the whole old stuff including the old getty. Imagine further the
LFS's agetty is different from the distro's version, or in a different
directory (Debian, for example, uses getty). The inittab should remain
in the memory. Init would try (on your next login) to use a getty that's
not there, meaning you wouldn't be able anymore to login into your
system.

Before you logout of the chroot'ed system you should be sure that the
init process will find the version of getty named in the inittab,
otherwise you would be unable to access the system anymore and need the
the bootdisk! A short

        cat /mnt/etc/inittab | grep getty

shows wether your previous system is using getty, agetty, mgetty or any
other version possible. If it's using any other version than agetty
(that's what Linux From Scratch is using), you should do a symlink like

        ln -s /sbin/agetty /sbin/<the previous getty version>

Now you can safely replace the old system.
________________________________________________________________________________

Command Explanations

cat /mnt/etc/inittab | grep getty:

Writes the content of /mnt/etc/inittab (your previous' systems inittab) to the
standard output, piping it to grep, which filters out all lines not bearing 
"getty" in it.

ln -s /sbin/agetty /sbin/<the previous getty version>:

Making a symbolic link that init will follow from the old getty version to the
new one.
________________________________________________________________________________

Deleting the previous System

You'll have to get the main partition entirely clean from everything that is not
/tmp/lfs.disk (and proc, which holds another file system).

        for dirname in `ls -1 /mnt | sed -e /tmp/d -e /proc/d -e /mnt/d`; 
        do rm -r /mnt/$dirname; done &&
        for filename in `ls /mnt/tmp | sed s/lfs.disk//`; do 
        rm $filename; done

Now it's clean enough for copying the LFS system. 
________________________________________________________________________________

Command explanations

for dirname/filename in <list>; do <command>; done:

performing <command> in a bash loop for every entry of <list>. The command in 
this case is simply deleting the directory or file named in the entry.

'ls -1 /mnt ...':

These kind of apostrophs let bash execute the commands inside and giving the 
result back as string, so we could use it as a <list> for our bash loop.
ls -1 /mnt lists all files in /mnt using 1 line per entry for easier editing 
with sed.

'... | sed -e /tmp/d -e /proc/d -e /mnt/d':

We are piping the result of "ls" to sed. -e states the following string to be
a (regular) expression. /.../d deletes the first line to have the expression 
... in it. So we're taking /mnt/tmp, /mnt/proc and /mnt/mnt out of the list.
________________________________________________________________________________


Now we may copy the new system. Everything but the /mnt directory, to which 
the device that we are filling with LFS is mounted and the directory /proc, in 
which are dynamic files written by the kernel.

        for dirname in `ls -1 / | sed -e /mnt/d -e /proc/d -e /tmp/d`; do 
        cp -a $dirname /mnt; done
________________________________________________________________________________

Command explanations

cp -a ... /mnt:

copies in "archive" mode, so the whole directories are copies with their 
content and all subdirs and all filemodes are kept, if possible. For the 
for ...; do; done constructions look at the previous command explanation.
________________________________________________________________________________

Now the LFS is on your primary partition logout of the chroot'ed environment 
into the new system. Now you can perform lilo and this stuff.

        logout (or exit)
        cd /
        umount /mnt/lfs/proc
        umount /mnt/lfs
        losetup -d /dev/loop0
________________________________________________________________________________

Command explanations

logout/exit:

Get out of 1. a bash, 2. a chroot'ed environment.

cd /

we change to the root dir not to have former access on the device we're
about to unmount.

umount...

First we need to unmount the proc device from the loop device, so you
can unmount this.

losetup -d /dev/loop0

delete the binding from /dev/loop0 to /tmp/lfs.disk.
________________________________________________________________________________

You may now delete lfs.disk, unless you don't want to use it otherwise.

After doing LFS another few times I found out that booting on an loop
device is quite unpractical due to the lack of speed and memory (I don't 
think that everyone has 1GB+ of RAM). What you can do is use gparted or 
any similar program to resize your actual partition, make another bootable 
partition on the PC you want to install the LFS on, and then

        dd if=/tmp/lfs.disk of=/dev/hda2

Use the node of the new partition instead of /dev/hda2.

You could also pipe the disk dump to install over network. If anybody is
planning an LFS installation like that I beg you to contact me via
irc.linuxfromscratch.org to 1. get further support and 2. let me share
your experience.

Then you can get back to the book (installing LILO and all that stuff).

Good luck!


The Future of this Hint
=======================

First of all, LFS, Linux and this hint are hobbies to me, so I can only
hope for spare time to test, correct and complement this hint. Even
then, a few additions would be of interest:

- maybe you could make sort of a bootdisk image (rootfs only), copy it
  to a ramdisk and use this to work on the main partition - which would
  be especially useful for a reiserfs installation!

- it could be helpful to be able to resize the lfs.disk file if
  necessary. dd could be used to add size to the file, resize2fs will be
  needed for the filesystem.

- same goes for a decrease in size of those files.

Since I use my systems for serious work, I'm not all eager to play
around with them that much. If you got a system you want to use for such
testing (to help me? How nice!), please contact me.

________________________________________________________________________________

Alex [LX]
(alex@22-music.com) - hope to meet you at #lfs on irc.linuxfromscratch.org