HOWTO: Make a chroot'ed Debian/Ubuntu

Ok, lets go!

First of all u have to emerge a debootstrap package, then become root and do the following:

root@gentop ~ $ cd /storage/schroot/
root@gentop /storage/schroot $ debootstrap oneiric oneiric.schroot
I: Retrieving InRelease
I: Failed to retrieve InRelease
I: Retrieving Release
W: Cannot check Release signature; keyring file not available /usr/share/keyrings/ubuntu-archive-keyring.gpg
I: Retrieving Packages
I: Validating Packages
I: Resolving dependencies of required packages...
I: Resolving dependencies of base packages...
I: Checking component main on http://archive.ubuntu.com/ubuntu...
<...skipped...>

This command will prepare base environment for Ubuntu 11.10 (to make same for 12.04 just replace oneiric to precise). The /storage/schroot/ is a base directory where I keep all my chroot’ed systems.

Next step is to install schroot and write a config files for it (/etc/schroot/schroot.conf):

[oneiric]
type=directory
description=Ubuntu Oneiric 11.10
directory=/storage/schroot/oneiric.schroot
users=build
groups=users
root-groups=root,wheel
script-config=ubuntu/config

The last line points to a config file relative to /etc/schroot w/ the following content:

# Filesystems to mount inside the chroot.
FSTAB="/etc/schroot/ubuntu/fstab"

# Files to copy from the host system into the chroot.
COPYFILES="/etc/schroot/ubuntu/copyfiles"

# System NSS databases to copy into the chroot.
NSSDATABASES="/etc/schroot/ubuntu/nssdatabases"

The most intersting here is a fstab:

/proc     /proc     none    rw,bind     0   0
/sys      /sys      none    rw,bind     0   0
/dev      /dev      none    rw,bind     0   0
/dev/pts  /dev/pts  none    rw,bind     0   0
/tmp      /tmp      none    rw,bind     0   0
/home     /home     none    rw,bind     0   0
/storage/soft/ubuntu/archives   /var/cache/apt/archives none    rw,bind     0   0

Other files could be taken from default configuration (/etc/schroot/default). Also it would be nice to have the following function in a ~/.bashrc:

    function build-chroot()
    {
        cd /home/builder
        select c in `/usr/bin/schroot -l`; do
            /usr/bin/schroot -c $c -u builder
            break
        done
    }

so u may just run it from the bash prompt to switch into a chroot’ed environment of your choice (as user builder, so do not forget to add such user or use some other name).

Note

While update packages in a chrooted system install scripts sometimes may fail because theres no upstart running. To solve this trouble one may symlink /sbin/initctl to /bin/true

Minimal Ubuntu install do not have en_US.UTF-8 (I dunno why! Or maybe I’m doing smth wrong), so it myst be generated (if your host locale is UTF as in example):

(oneiric)root@gentop:/home/builder# locale-gen en_US en_US.UTF-8
Generating locales...
en_US.ISO-8859-1... done
en_US.UTF-8... done
Generation complete.

Make your changes permanent:

(oneiric)root@gentop:/home/builder# update-locale LANG=en_US.UTF-8 LC_MESSAGES=POSIX

To prepare a build “work horse” install the following packages as (chrooted) root:

# apt-get install build-essential devscripts doxygen cmake software-properties-common pkg-config

Then add some PPAs:

(oneiric)root@gentop:/home/builder# add-apt-repository ppa:boost-latest
You are about to add the following PPA to your system:
Providing the most up-to-date version of the Boost C++ Libraries.
More info: https://launchpad.net/~boost-latest/+archive/ppa
Press [ENTER] to continue or ctrl-c to cancel adding it

gpg: keyring `/tmp/tmpi67dku/secring.gpg' created
gpg: keyring `/tmp/tmpi67dku/pubring.gpg' created
gpg: requesting key 029DB5C7 from hkp server keyserver.ubuntu.com
gpg: /tmp/tmpi67dku/trustdb.gpg: trustdb created
gpg: key 029DB5C7: public key "Launchpad boost-latest" imported
gpg: Total number processed: 1
gpg:               imported: 1  (RSA: 1)
OK

Also consider to add ppa:likemartinma/devel for fresh CMake. Now update packages and install boost libraries…