===== Setting up a Slackware chroot =====

There are multiple reasons why you might want to set up a Slackware chroot:
  * building 32-bit packages on a 64-bit multilib system
  * building -stable packages on a -current system
  * building (and testing) packages for SBo on a clean system

For this guide, we'll create a chroot at **/chroot_folder** from **slackware-14.1-install-dvd.iso**.

==== Obtaining a Slackware installation of your desired architecture ====

Start with a Slackware installation DVD. Download it from from http://www.slackware.com/getslack/ via torrent.

==== Installing the packages ====

=== Automatically ===

You can create your chroot and install Slackware into it using the following elegant script: [[http://tty1.uk/scripts/slackware/mkchroot]]

Update - the script seems to have moved to: [[https://github.com/duncan-roe/mkchroot/blob/master/mkchroot]], also please note this script should work with all versions of Slackware, including v15.

=== Manually ===

First, create a folder which will contain the chroot:

<code bash>mkdir /chroot_folder</code>

Mount the installation ISO:

<code bash>
mount -o loop slackware-14.1-install-dvd.iso /mnt/cdrom
cd /mnt/cdrom
</code>

After the ISO has been mounted, the packages (found under the //slackware// or //slackware64// folder) can be installed to the chroot folder with:

<code bash>
installpkg --root /chroot-folder */*.t?z
</code>

Then unmount the ISO:

<code bash>
umount /mnt/cdrom
</code>

=== Setting up required files ===

== fstab ==

The following minimal snippet can be used for ///chroot_folder/etc/fstab//

<file>
# <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
</file>

==== Entering the Chroot ====

=== Automatic mount ===

To have the chroot mounted permanently, add the following to your __host system's__ ///etc/fstab//:

<file>
/dev             chroot_folder/dev             none bind,auto 0 0
/proc            chroot_folder/proc            none bind,auto 0 0
/sys             chroot_folder/sys             none bind,auto 0 0
/etc/resolv.conf chroot_folder/etc/resolv.conf none bind,auto 0 0
</file>

And reboot. Then run the following command to mount the chroot folder:

<code bash>
mount /chroot_folder
</code>

=== Manual mount ===

Refer to: ([[howtos:slackware_admin:how_to_chroot_from_media#volume_mounting]]).

=== Entering the Chroot ===

Now that the chroot is set up, one can chroot into it:

<code bash>chroot /chroot_folder /bin/bash</code>

**Note**

Wrote a small script to automate the chroot steps.

https://raw.githubusercontent.com/aadityabagga/scripts/master/chroot.sh

=== Updating packages ===

After that, you can run slackpkg and update the packages: ([[slackware:beginners_guide#configure_a_package_manager]]).

=== Exiting ===

When you're done, exited the chroot by pressing //Ctrl+d//.

==== Usecase: Building 32-bit Packages ====

=== Mounting partitions ===

I use a chroot to build 32-bit packages on a 64-bit system. I needed to mount the partition which contained the SlackBuilds for which I wanted to make a package, As my Slackware host mount point is (in this example) at /slackware_host_mount_point, I used the command:

<code bash>mount -B /slackware_host_mount_point /chroot_folder
</code>

(http://www.thegeekstuff.com/2013/01/mount-umount-examples/)

Then I built the package by executing the Slackbuild as follows:

<code bash>
ARCH=i686 ./my_package.SlackBuild</code>

=== An alternative way to build other ARCH packages ===

Instead of using `ARCH=i686' before running a slackbuild, we can use a program
called `setarch', which, among other things, can set the ARCH and the kernel
version in the shell.  It has some handy symlinks, such as linux32 or i586,
which saves some typing.  The `linux32' command will set the reported kernel's
ARCH as `i686'.

**SYNOPSIS**
<code>
  setarch arch [options] [program [argument...]]
</code>

When we run `linux32' it starts a new shell, so we can also use it to chroot:

<code>
  chroot /path/to/chroot linux32 /bin/zsh
</code>

or it could be run after chrooting into our new root.  Settings will revert to
normal when we exit the new shell.  One useful option is to change the kernel's
reported version:

<code>
  chroot /path/to/chroot linux32 --uname-2.6 /bin/zsh
</code>

That `--uname-2.6' isn't a typo, there has to be a dash between the flag and
the version.  The setarch(8) man page shows all the options.

--
Dave

====== See also ======

  * https://wiki.archlinux.org/index.php/Chroot
  * http://www.linuxquestions.org/questions/slackware-installation-40/install-slackware-to-a-folder-using-chroot-825598/#post4093831

====== Sources ======
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* Originally written by [[wiki:user:aaditya | Aaditya]]
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