Add documentation for parallel-debian
This commit is contained in:
Colin Walters
parent
d32dd476f7
commit
8020f444cf
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@ -1,38 +0,0 @@
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Experimenting with multiple roots
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---------------------------------
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$ qemu-img create debian.img 600M
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$ mkfs.ext2 debian.img
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$ mkdir debian-mnt
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$ mount -o loop debian.img debian-mnt
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$ debootstrap wheezy debian-mnt
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$ chroot debian-mnt
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$ apt-get install linux-image-3.0.0
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Control-d
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$ cp debian-mnt/boot/vmlinuz* .
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$ cp debian-mnt/boot/initrd* .
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$ umount debian-mnt
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You now have a Debian disk image in debian.img and a kernel+initrd that are bootable with qemu.
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Modifying the image
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-------------------
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The first thing I did was re-mount the image, and move almost everythig
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(/boot, /var, /etc), except lost+found to a new directory "r0".
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Then I started hacking on the initrd, making understand how to chroot
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to "r0".
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This means that after booting, every process would be in /r0 -
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including any hacktree process. Assuming objects live in say
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/objects, we need some way for hacktree to switch things. I think
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just chroot breakout would work. This has the advantage the daemon
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can continue to use libraries from the active host.
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Note there is a self-reference here (as is present in Debian/Fedora
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etc.) - the update system would at present be shipped with the system
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itself. Should they be independent? That has advantages and
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disadvantages. I think we should just try really really hard to avoid
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breaking hacktree in updates.
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@ -0,0 +1,148 @@
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From 0e22e86348bb356e69ed28a58e959b7fab7c43cc Mon Sep 17 00:00:00 2001
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From: Colin Walters <walters@verbum.org>
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Date: Sun, 16 Oct 2011 14:26:40 -0400
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Subject: [PATCH] Add support for subroot= option
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Passing this option causes the initrd to chroot() into a subdirectory of /.
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This is useful for parallel installing multiple systems in one filesystem.
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This relies on a patched switch_root from util-linux.
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---
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init | 32 +++++++++++++++++++++-----------
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scripts/init-bottom/udev | 5 ++---
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scripts/local | 6 ++++--
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3 files changed, 27 insertions(+), 16 deletions(-)
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diff --git a/init b/init
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index 445c354..3ff2750 100755
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--- a/init
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+++ b/init
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@@ -49,6 +49,8 @@ export init=/sbin/init
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export quiet=n
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export readonly=y
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export rootmnt=/root
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+export subroot=
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+export rootsubmnt=
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export debug=
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export panic=
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export blacklist=
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@@ -68,6 +70,10 @@ for x in $(cat /proc/cmdline); do
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init=*)
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init=${x#init=}
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;;
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+ subroot=*)
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+ subroot=${x#subroot=}
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+ rootsubmnt=${x#subroot=}
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+ ;;
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root=*)
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ROOT=${x#root=}
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case $ROOT in
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@@ -218,14 +224,18 @@ maybe_break mountroot
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mountroot
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log_end_msg
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+if test -n "${rootsubmnt}"; then
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+ rootsubmnt=${rootmnt}/${rootsubmnt}
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+fi
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+
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maybe_break bottom
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[ "$quiet" != "y" ] && log_begin_msg "Running /scripts/init-bottom"
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run_scripts /scripts/init-bottom
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[ "$quiet" != "y" ] && log_end_msg
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# Preserve information on old systems without /run on the rootfs
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-if [ -d ${rootmnt}/run ]; then
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- mount -n -o move /run ${rootmnt}/run
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+if [ -d ${rootsubmnt}/run ]; then
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+ mount -n -o move /run ${rootsubmnt}/run
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else
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# The initramfs udev database must be migrated:
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if [ -d /run/udev ] && [ ! -d /dev/.udev ]; then
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@@ -239,27 +249,27 @@ else
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fi
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# Move virtual filesystems over to the real filesystem
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-mount -n -o move /sys ${rootmnt}/sys
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-mount -n -o move /proc ${rootmnt}/proc
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+mount -n -o move /sys ${rootsubmnt}/sys
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+mount -n -o move /proc ${rootsubmnt}/proc
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validate_init() {
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checktarget="${1}"
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# Work around absolute symlinks
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- if [ -d "${rootmnt}" ] && [ -h "${rootmnt}${checktarget}" ]; then
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- case $(readlink "${rootmnt}${checktarget}") in /*)
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- checktarget="$(chroot ${rootmnt} readlink ${checktarget})"
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+ if [ -d "${rootsubmnt}" ] && [ -h "${rootsubmnt}${checktarget}" ]; then
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+ case $(readlink "${rootsubmnt}${checktarget}") in /*)
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+ checktarget="$(chroot ${rootsubmnt} readlink ${checktarget})"
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;;
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esac
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fi
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# Make sure the specified init can be executed
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- if [ ! -x "${rootmnt}${checktarget}" ]; then
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+ if [ ! -x "${rootsubmnt}${checktarget}" ]; then
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return 1
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fi
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# Upstart uses /etc/init as configuration directory :-/
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- if [ -d "${rootmnt}${checktarget}" ]; then
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+ if [ -d "${rootsubmnt}${checktarget}" ]; then
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return 1
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fi
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}
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@@ -273,7 +283,7 @@ if [ -n "${init}" ]; then
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fi
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# Common case: /sbin/init is present
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-if [ ! -x "${rootmnt}/sbin/init" ]; then
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+if [ ! -x "${rootsubmnt}/sbin/init" ]; then
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# ... if it's not available search for valid init
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if [ -z "${init}" ] ; then
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for inittest in /sbin/init /etc/init /bin/init /bin/sh; do
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@@ -315,5 +325,5 @@ unset resume
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unset resume_offset
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# Chain to real filesystem
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-exec run-init ${rootmnt} ${init} "$@" <${rootmnt}/dev/console >${rootmnt}/dev/console
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+exec switch_root --subroot ${subroot} ${rootmnt} ${init} "$@" <${rootsubmnt}/dev/console >${rootsubmnt}/dev/console
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panic "Could not execute run-init."
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diff --git a/scripts/init-bottom/udev b/scripts/init-bottom/udev
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index 375dfab..7922d0f 100755
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--- a/scripts/init-bottom/udev
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+++ b/scripts/init-bottom/udev
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@@ -20,9 +20,8 @@ if [ -e /etc/udev/udev.conf ]; then
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fi
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# move the /dev tmpfs to the rootfs
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-mount -n -o move /dev ${rootmnt}${udev_root}
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+mount -n -o move /dev ${rootsubmnt}${udev_root}
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# create a temporary symlink to the final /dev for other initramfs scripts
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nuke /dev
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-ln -s ${rootmnt}${udev_root} /dev
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-
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+ln -s ${rootsubmnt}${udev_root} /dev
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diff --git a/scripts/local b/scripts/local
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index 521e69a..25b518f 100644
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--- a/scripts/local
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+++ b/scripts/local
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@@ -101,9 +101,11 @@ mountroot()
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# FIXME This has no error checking
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# Mount root
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if [ "${FSTYPE}" != "unknown" ]; then
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- mount ${roflag} -t ${FSTYPE} ${ROOTFLAGS} ${ROOT} ${rootmnt}
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+ echo mount ${roflag} -t ${FSTYPE} ${ROOTFLAGS} ${ROOT} ${rootmnt}
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+ mount ${roflag} -t ${FSTYPE} ${ROOTFLAGS} ${ROOT} ${rootmnt} || echo "FAILED TO MOUNT ROOT"
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else
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- mount ${roflag} ${ROOTFLAGS} ${ROOT} ${rootmnt}
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+ echo mount ${roflag} ${ROOTFLAGS} ${ROOT} ${rootmnt}
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+ mount ${roflag} ${ROOTFLAGS} ${ROOT} ${rootmnt} || echo "FAILED TO MOUNT ROOT"
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fi
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[ "$quiet" != "y" ] && log_begin_msg "Running /scripts/local-bottom"
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--
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1.7.6.4
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@ -0,0 +1,102 @@
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From fa0e7df4e3d6550f0391bb3b81b2b6ac5165439d Mon Sep 17 00:00:00 2001
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From: Colin Walters <walters@verbum.org>
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Date: Sun, 16 Oct 2011 21:01:46 -0400
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Subject: [PATCH] switch_root: Add --subroot option
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This is useful for parallel installing multiple operating system
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roots. See: http://git.gnome.org/browse/hacktree
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---
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sys-utils/switch_root.8 | 4 ++++
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sys-utils/switch_root.c | 31 +++++++++++++++++++++----------
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2 files changed, 25 insertions(+), 10 deletions(-)
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diff --git a/sys-utils/switch_root.8 b/sys-utils/switch_root.8
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index 34ab0d0..6981852 100644
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--- a/sys-utils/switch_root.8
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+++ b/sys-utils/switch_root.8
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@@ -27,6 +27,10 @@ process.
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show help and exit
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.IP "\fB\-V, \-\-version\fP"
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show version number and exit
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+.IP "\-\-subroot\fP"
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+Instead of calling chroot into the / of the new root, instead use the
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+given argument. This helps parallel install multiple operating systems in one
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+root filesystem.
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.SH RETURN VALUE
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.B switch_root
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diff --git a/sys-utils/switch_root.c b/sys-utils/switch_root.c
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index 2dfed71..20ae5d6 100644
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--- a/sys-utils/switch_root.c
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+++ b/sys-utils/switch_root.c
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@@ -108,7 +108,7 @@ done:
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return rc;
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}
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-static int switchroot(const char *newroot)
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+static int switchroot(const char *newroot, const char *subroot)
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{
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/* Don't try to unmount the old "/", there's no way to do it. */
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const char *umounts[] = { "/dev", "/proc", "/sys", NULL };
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@@ -141,7 +141,7 @@ static int switchroot(const char *newroot)
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return -1;
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}
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- if (chroot(".")) {
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+ if (chroot(subroot ? subroot : ".")) {
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warn("failed to change root");
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return -1;
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}
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@@ -160,7 +160,7 @@ static int switchroot(const char *newroot)
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static void usage(FILE *output)
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{
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- fprintf(output, "usage: %s <newrootdir> <init> <args to init>\n",
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+ fprintf(output, "usage: %s [--subroot DIR] <newrootdir> <init> <args to init>\n",
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program_invocation_short_name);
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exit(output == stderr ? EXIT_FAILURE : EXIT_SUCCESS);
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}
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@@ -175,22 +175,33 @@ static void version(void)
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int main(int argc, char *argv[])
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{
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char *newroot, *init, **initargs;
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+ char *subroot = NULL;
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+ int argi;
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- if (argv[1] && (!strcmp(argv[1], "--help") || !strcmp(argv[1], "-h")))
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+ if (argc < 2)
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+ usage(stderr);
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+
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+ argi = 1;
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+ if ((!strcmp(argv[1], "--help") || !strcmp(argv[1], "-h")))
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usage(stdout);
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- if (argv[1] && (!strcmp(argv[1], "--version") || !strcmp(argv[1], "-V")))
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+ if ((!strcmp(argv[1], "--version") || !strcmp(argv[1], "-V")))
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version();
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- if (argc < 3)
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+ if (argc > 3 && argv[1] && (!strcmp(argv[1], "--subroot"))) {
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+ subroot = argv[2];
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+ argi = 3;
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+ }
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+ if (argc <= argi+1) {
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usage(stderr);
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+ }
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- newroot = argv[1];
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- init = argv[2];
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- initargs = &argv[2];
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+ newroot = argv[argi];
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+ init = argv[argi+1];
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+ initargs = &argv[argi+1];
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if (!*newroot || !*init)
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usage(stderr);
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- if (switchroot(newroot))
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+ if (switchroot(newroot, subroot))
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errx(EXIT_FAILURE, "failed. Sorry.");
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if (access(init, X_OK))
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--
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1.7.6.4
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@ -0,0 +1,80 @@
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Experimenting with multiple roots
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---------------------------------
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<http://wiki.debian.org/QEMU#Setting_up_a_testing.2BAC8-unstable_system>
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Follow the steps for making a disk image, downloading the business
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card CD, booting it in QEMU and running through the installer.
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Test that the image works after installation too, before you start
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modifying things below! Remember to remove the -cdrom and -boot
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options from the installation QEMU command.
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Modifying the image
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-------------------
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You now have a disk image in debian.img, and the first partition
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should be ext4.
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The first thing I did was mount the image, and move almost everythig
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(/boot, /var, /etc), except lost+found to a new directory "r0".
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$ mkdir /mnt/debian
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$ modprobe nbd max_part=8
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$ qemu-nbd --connect=/dev/nbd0 debian.qcow
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$ mount /dev/nbd0p1 /mnt/debian/
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$ cd /mnt/debian
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$ mkdir r0
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$ DIRS="bin boot dev etc lib lib64 media mnt opt proc root run sbin selinux srv sys tmp usr var"
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$ mv $DIRS r0
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Now with it still mounted, we need to move on to the next part -
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modifying the initrd.
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Then I started hacking on the initrd, making understand how to chroot
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to "r0". I ended up with two patches - one to util-linux, and one to
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the "init" script in Debian's initrd.
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See:
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0001-switch_root-Add-subroot-option.patch
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0001-Add-support-for-subroot-option.patch
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$ git clone --depth=1 git://github.com/karelzak/util-linux.git
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$ cd util-linux
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$ patch -p1 -i ../0001-switch_root-Add-subroot-option.patch
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$ ./autogen.sh; ./configure ; make
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Now you have a modified "sys-utils/switch_root" binary. Let's next
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patch the initrd and rebuild it:
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Make a backup:
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$ mkdir initrd
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$ cp /mnt/debian/boot/initrd.img-3.0.0-1-amd64{,.orig}
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|
Unpack, and patch:
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$ zcat /mnt/debian/boot/initrd.img-3.0.0-1-amd64 | (cd initrd; cpio -d -i -v)
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$ (cd initrd && patch -p1 -i ../0001-Add-support-for-subroot-option.patch)
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Repack:
|
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|
|
||||||
|
$ (cd initrd; find | cpio -o -H newc) | gzip > /mnt/debian/boot/initrd.img-3.0.0-1-amd64.new
|
||||||
|
$ mv /mnt/debian/boot/initrd.img-3.0.0-1-amd64{.new,}
|
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Running hacktree inside the system
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----------------------------------
|
||||||
|
|
||||||
|
This means that after booting, every process would be in /r0 -
|
||||||
|
including any hacktree process. Assuming objects live in say
|
||||||
|
/objects, we need some way for hacktree to switch things. I think
|
||||||
|
just chroot breakout would work. This has the advantage the daemon
|
||||||
|
can continue to use libraries from the active host.
|
||||||
|
|
||||||
|
Note there is a self-reference here (as is present in Debian/Fedora
|
||||||
|
etc.) - the update system would at present be shipped with the system
|
||||||
|
itself. Should they be independent? That has advantages and
|
||||||
|
disadvantages. I think we should just try really really hard to avoid
|
||||||
|
breaking hacktree in updates.
|
||||||
|
|
||||||
|
|
@ -0,0 +1,16 @@
|
||||||
|
#!/bin/sh
|
||||||
|
|
||||||
|
set -e
|
||||||
|
set -x
|
||||||
|
|
||||||
|
if test -f debian.img; then
|
||||||
|
echo debian.img already exists
|
||||||
|
exit 1
|
||||||
|
fi
|
||||||
|
|
||||||
|
qemu-img create debian.img 600M
|
||||||
|
mkfs.ext2 -q -F debian.img
|
||||||
|
mkdir -p debian-mnt
|
||||||
|
mount -o loop debian.img debian-mnt
|
||||||
|
debootstrap --arch amd64 wheezy debian-mnt
|
||||||
|
umount debian-mnt
|
||||||
|
|
@ -0,0 +1,20 @@
|
||||||
|
#!/bin/sh
|
||||||
|
|
||||||
|
set -e
|
||||||
|
set -x
|
||||||
|
|
||||||
|
DIRS="bin boot dev etc lib lib64 media mnt opt proc root run sbin selinux srv sys tmp usr var"
|
||||||
|
|
||||||
|
if ! test -f debian.img; then
|
||||||
|
echo need debian.img
|
||||||
|
exit 1
|
||||||
|
fi
|
||||||
|
|
||||||
|
mount -o loop debian.img debian-mnt
|
||||||
|
cd debian-mnt
|
||||||
|
if ! test -d r0; then
|
||||||
|
mkdir r0
|
||||||
|
mv $DIRS r0
|
||||||
|
fi
|
||||||
|
cd ..
|
||||||
|
umount debian-mnt
|
||||||
Loading…
Reference in New Issue