Difference between revisions of "Development Team/Chroot"

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Sugar ought to be easy to run from chroots. For a variety of silly reasons, this isn't yet the case, but it might be soon. Ping [[User:Mstone|Michael]] with questions.
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=== Status ===
  
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=== Chroot Construction ===
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* sugar-chroot-0.1 released: see [http://dev.laptop.org/git/users/mstone/sugar-chroot sugar-chroot]
  
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There are lots of ways to create appropriate chroots; e.g. by hand, with debootstrap, with mock, etc.
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=== Purpose ===
  
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With debootstrap, in order to get a working chroot, you want something like:
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''You want to hack sugar. You don't want to fuss around. '''You want sugar-chroot.'''''
  
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  export CHROOT=`pwd`/sid-root
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=== Usage ===
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  debootstrap --arch i386 sid $CHROOT http://debian.lcs.mit.edu/debian
 
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  sudo chroot $CHROOT /bin/bash -l
 
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  # and some of the following:
 
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  mount -t proc proc $CHROOT/proc
 
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  mount -t devpts devpts $CHROOT/dev/pts
 
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  mount -t selinuxfs selinux $CHROOT/selinux
 
  
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As excerpted from the '''[http://dev.laptop.org/git/users/mstone/sugar-chroot/plain/README README]''':
  
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With mock, it would be more like:
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sugar-chroot consists of simple scripts. Download and unpack them like so:
  
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  mock -r fedora-devel-i386 --init
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NV=sugar-chroot-0.1
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  mock -r fedora-devel-i386 --shell
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curl http://dev.laptop.org/~mstone/releases/SOURCES/$NV.tar.xz | tar Zxf $NV.tar.xz
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cd $NV
  
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=== X11 ===
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To use them, pick a supported distro:
  
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Most X11 servers are configured to disable TCP connections. This means that in order to get a working X connection we can:
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DISTRO=debian
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DISTRO=fedora
  
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# bind-mount the X unix socket into the chroot.
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To configure:
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# ssh ''into'' the chroot with X11-forwarding enabled.
 
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# enable TCP on an X server, e.g. a nested Xephyr.
 
  
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We're going to try option (3) first:
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echo $DISTRO > conf/distro
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$EDITOR conf/$DISTRO.mk
  
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  Xephyr -ac :1
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Then run
  
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::''NB: If you figure out how to make Xephyr bind only to localhost sockets (or how to make it use a custom xauth config), speak up!''
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sudo make r/distro
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and, inside the chroot:
 
  
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  export DISPLAY=localhost:1
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to install your chroot.
  
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=== D-Bus ===
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=== History ===
  
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Sugar wants to be able to use global state stored in both HAL and NetworkManager, both of which live on the system bus. Consequently, we need to bind-mount
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See http://wiki.sugarlabs.org/index.php?title=Development_Team/Chroot&oldid=36911 for the manual instructions which sugar-chroot automates.
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  mount --bind /var/run/dbus $CHROOT/var/run/dbus
 
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before entering the chroot. (Mock uses unshare() to enter a new mount-point namespace since this makes garbage collection of mountpoints much easier.)
 
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=== User Account ===
 
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For stupid reasons, it's necessary that Sugar run under a uid inside the chroot which exists as a real account outside the chroot. (Talk to the DBus people.)
 
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Consequently, run something like this both inside and outside the chroot:
 
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  groupadd -g 64002 sugar
 
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  useradd -m -u 64002 -g sugar sugar
 
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Then, inside the chroot, you can happily run sugar as user 'sugar' with something like
 
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cat > as_person <<EOF
 
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#!/usr/bin/env python
 
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from os import environ, chdir, setgroups, setgid, setuid, execve
 
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from sys import argv
 
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from pwd import getpwnam
 
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user = getpwnam(argv[1])
 
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environ['HOME'] = user.pw_dir
 
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environ['USER'] = user.pw_name
 
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chdir(user.pw_dir)
 
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setgroups([user.pw_gid])
 
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setgid(user.pw_gid)
 
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setuid(user.pw_uid)
 
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execve(argv[2], argv[2:], environ)
 
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EOF
 
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chmod a+x as_person
 
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./as_person sugar /usr/bin/sugar
 

Latest revision as of 20:33, 23 February 2010

Status

Purpose

You want to hack sugar. You don't want to fuss around. You want sugar-chroot.

Usage

As excerpted from the README:

sugar-chroot consists of simple scripts. Download and unpack them like so: 

NV=sugar-chroot-0.1
curl http://dev.laptop.org/~mstone/releases/SOURCES/$NV.tar.xz | tar Zxf $NV.tar.xz
cd $NV

To use them, pick a supported distro: 

DISTRO=debian
DISTRO=fedora

To configure: 

echo $DISTRO > conf/distro
$EDITOR conf/$DISTRO.mk

Then run 

sudo make r/distro

to install your chroot.

History

See http://wiki.sugarlabs.org/index.php?title=Development_Team/Chroot&oldid=36911 for the manual instructions which sugar-chroot automates.

Retrieved from "https://wiki.sugarlabs.org/index.php?title=Development_Team/Chroot&oldid=46703"