A chroot installation environment

I have been having annoying problems with VirtualBox, summed up already at LQ, so I won’t go through them again. I need a clean installation of Slackware (x86_64 and x86), therefor, I decided to learn how to set it up in a chroot environment.

I used as a guide Slackware’s and CRUX’s wiki pages. Below is what I did for a 32bit Slackware on a 64bit “host”.

Create the folder, let’s name it slack32, where the chroot environment will be. I have a data storage HDD, mounted on /media/data0, so that’s where I decided to create it:

mkdir /media/data0/slack32/

Mount the installation ISO (as root, of course):

mount -o loop slackware-15.0-install-dvd.iso /media/cdrom0/

Navigate there, to the subfolder containing the packages:

cd /media/cdrom0/slackware/

Now, install all packages to the folder where we’ll chroot later:

installpkg --root /media/data0/slack32/ */*.t?z

Let’s already define the path to the folder as:

CHROOT=/media/data0/slack32/

Let’s navigate there:

cd $CHROOT

Copy resolv.conf from the host, so we have net:

cp /etc/resolv.conf $CHROOT/etc

There’s no fstab file, so let’s create one:

touch $CHROOT/etc/fstab

Paste these as it’s contents:

# <file system> <mount point>   <type>  <options>       <dump>  <pass>
tmpfs           /dev/shm        tmpfs    defaults        0      0
devpts          /dev/pts        devpts   noexec,nosuid,gid=tty,mode=0620  0      0
sysfs           /sys            sysfs    defaults        0      0
proc            /proc           proc     defaults        0      0

Now mount:

mount -t proc proc $CHROOT/proc
mount --bind /dev $CHROOT/dev
mount --bind /sys $CHROOT/sys

Finally, chroot there:

chroot $CHROOT /bin/bash

Specify that it’s a 32bit system:

linux32

From this point we are working in the chroot environment and all file locations are in the chroot environment. To set up slackpkg, a 32bit mirror should be selected. Since I installed from a 64bit host, the mirrors will be for x86_64 architecture. What I did was, first to modify a mirror close to me by removing the “64” suffix from “slackware:”

# FINLAND (FI)
ftp://elektroni.phys.tut.fi/slackware-15.0/

I had GPG signature problems, which seemed to disappear after I updated ca-certificates. For this, I had to stop the GPG check first:

# If CHECKGPG is "on", the system will verify the GPG signature of each package
# before install/upgrade/reinstall is performed.
CHECKGPG=off

Then, do

slackpkg update
slackpkg upgrade ca-certificates

After that, I put it back to on and then:

slackpkg update gpg

One thing that can also be done is to reinstall slackpkg itself, now when the system knows it’s 32bit, in this way all mirrors should be correct:

slackpkg reinstall slackpkg

Upgrade the whole system, as usual:

slackpkg upgrade-all

That’s it. I went to /tmp and tested a few SlackBuilds (Bpp1.9-*) that just made it back to 15.0. When done with working in slack32, I did:

exit
umount $CHROOT/proc
umount $CHROOT/dev
umount $CHROOT/sys
exit

Next time I need it, just start like this

CHROOT=/media/data0/slack32/
cd $CHROOT
mount -t proc proc $CHROOT/proc
mount --bind /dev $CHROOT/dev
mount --bind /sys $CHROOT/sys
chroot $CHROOT /bin/bash
linux32

Compile times are better than in a VM, that’s for sure. I also have very easy navigation and file sharing there. Phew!


5 Comments on “A chroot installation environment”

  1. Anonymous says:

    There is a problem with “installpkg –root”. Theoretically, doinst.sh scripts should work when “–root” is used, but in reality a lot of them doesn’t work. This is a reason for your ca-certificates problem.

    I’d suggest first install a and l series using installpkg –root, them chroot and install all series, including a and l, with installpkg without –root. This way, all doinst.sh scripts will run and you get a proper installation.

    Also, you should have /var/lib/dbus/machine-id ( = /etc/machine-id ) and root/.Xauthority inside chroot.

    And set the environment variable HOME, TERM, and PATH to be what you want (for root).

  2. slackalaxy says:

    hey, thanks very much! I will give it a try and update the post.

  3. Anonymous says:

    A nice thing is that it is possible to run a program installed in chroot such that a part of environment will be from chroot, but the rest is from you usual environmet outside chroot. Say, /usr/bin from chroot, /home from outside. In this way you can run from chroot programs that use X. I use something like this:

    /usr/bin/bwrap \
    –ro-bind /chroot / \
    –dev-bind /dev /dev \
    –ro-bind /sys /sys \
    –proc /proc \
    –ro-bind-try /etc/resolv.conf /etc/resolv.conf \
    –ro-bind-try /etc/hosts /etc/hosts \
    –ro-bind-try /etc/nsswitch.conf /etc/nsswitch.conf \
    –ro-bind-try /etc/passwd /etc/passwd \
    –ro-bind-try /etc/group /etc/group \
    –bind-try /home /home \
    –bind-try /media /media \
    –bind-try /mnt /mnt \
    –bind-try /opt /opt \
    –bind-try /run /run \
    –bind-try /srv /srv \
    –bind-try /tmp /tmp \
    –bind-try /usr/local /usr/local \
    –bind-try /var /var \
    “$@”

    The –bind-try directories are from outside chroot.

    An example, if you have 32-bit chroot, you can run wine from it without installi
    ng multilib.

    bwrap is from bubblewrap package at SBo.

  4. slackalaxy says:

    hey, that’s a great tip! I’ll definitely give it a try and if you don’t mind, even write a post about it

  5. Anonymous says:

    You are welcome


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