This is based on dracut, but with all the glue-scripts removed.
Idea is:
* start systemd/udevd/journald
* wait for the root device to appear
* mount the rootfs
* isolate the switch-root target
* this shuts down/cleans up everything
* then calls systemctl to switch to the new root and reexec systemd
Note: generate initramfs with
HOOKS=('base' 'fsck' 'systemd')
to get all the needed binaries (such as mount and fsck and busybox for
debugging).
TODO:
* patch systemctl to read init= from /proc/cmdline if it is not given as
an argument to switch-root (now it always reexecs systemd)
* make a rootfs-mount-from-proc-cmdline generator instead of a
hardcoded new_root.mount
* include more systemd units and helpers, should reveiw them all
* discuss with dracut/systemd people the possibility of putting something
like this in the systemd repo so we don't have to duplicate work
---
initrd-pre-switch-root.service | 19 ++++++++++++
initrd-switch-root.service | 20 +++++++++++++
initrd-switch-root.target | 16 ++++++++++
install/systemd | 68 ++++++++++++++++++++++++++++++++++++++++++
new_root.mount | 15 ++++++++++
udevadm-cleanup-db.service | 18 +++++++++++
6 files changed, 156 insertions(+)
create mode 100644 initrd-pre-switch-root.service
create mode 100644 initrd-switch-root.service
create mode 100644 initrd-switch-root.target
create mode 100644 install/systemd
create mode 100644 new_root.mount
create mode 100644 udevadm-cleanup-db.service
diff --git a/initrd-pre-switch-root.service b/initrd-pre-switch-root.service
new file mode 100644
index 0000000..ae6a731
--- /dev/null
+++ b/initrd-pre-switch-root.service
@@ -0,0 +1,19 @@
+# This file is part of systemd.
+#
+# systemd is free software; you can redistribute it and/or modify it
+# under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation; either version 2.1 of the License, or
+# (at your option) any later version.
+
+# See systemd.special(7) for details
+
+[Unit]
+Description=Waiting for new root device to appear
+DefaultDependencies=no
+Requires=new_root.mount
+After=new_root.mount
+ConditionPathExists=/etc/initrd-release
+
+[Service]
+Type=oneshot
+ExecStart=/usr/bin/systemctl --no-block isolate initrd-switch-root.target
diff --git a/initrd-switch-root.service b/initrd-switch-root.service
new file mode 100644
index 0000000..03ff9a8
--- /dev/null
+++ b/initrd-switch-root.service
@@ -0,0 +1,20 @@
+# This file is part of systemd.
+#
+# systemd is free software; you can redistribute it and/or modify it
+# under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation; either version 2.1 of the License, or
+# (at your option) any later version.
+
+[Unit]
+Description=Switch Root
+DefaultDependencies=no
+ConditionPathExists=/etc/initrd-release
+OnFailure=emergency.service
+After=initrd-switch-root.target new_root.mount
+AllowIsolate=yes
+
+[Service]
+Type=oneshot
+# we have to use "--force" here, otherwise systemd would umount /run
+ExecStart=/usr/bin/systemctl --no-block --force switch-root /new_root
+KillMode=none
diff --git a/initrd-switch-root.target b/initrd-switch-root.target
new file mode 100644
index 0000000..fd23908
--- /dev/null
+++ b/initrd-switch-root.target
@@ -0,0 +1,16 @@
+# This file is part of systemd.
+#
+# systemd is free software; you can redistribute it and/or modify it
+# under the terms of the GNU Lesser General Public License as published by
+# the Free Software Foundation; either version 2.1 of the License, or
+# (at your option) any later version.
+
+# See systemd.special(7) for details
+
+[Unit]
+Description=Switch Root
+DefaultDependencies=no
+Requires=initrd-switch-root.service
+Before=initrd-switch-root.service
+AllowIsolate=yes
+ConditionPathExists=/etc/initrd-release
diff --git a/install/systemd b/install/systemd
new file mode 100644
index 0000000..9b38bdf
--- /dev/null
+++ b/install/systemd
@@ -0,0 +1,68 @@
+#!/bin/bash
+
+build() {
+ local rules tool socket service
+
+ add_binary /usr/lib/systemd/systemd /init
+ add_binary /usr/bin/systemctl
+ add_binary /bin/mount
+ add_binary /usr/bin/udevadm
+ add_binary /usr/lib/systemd/systemd-udevd
+ add_binary /usr/lib/systemd/systemd-journald
+ # for debugging
+ add_binary /bin/bash
+ add_binary /usr/bin/journalctl
+
+ for rules in 50-udev-default.rules 60-persistent-storage.rules 64-btrfs.rules 80-drivers.rules 99-systemd.rules; do
+ add_file "/usr/lib/udev/rules.d/$rules"
+ done
+ for tool in ata_id scsi_id; do
+ add_file "/usr/lib/udev/$tool"
+ done
+ for socket in systemd-udevd-control systemd-udevd-kernel systemd-journald; do
+ add_file "/usr/lib/systemd/system/$socket.socket"
+ add_symlink "/usr/lib/systemd/system/sockets.target.wants/$socket.socket" "../$socket.socket"
+ done
+ for service in systemd-udevd systemd-udev-trigger systemd-journald debug-shell; do
+ add_file "/usr/lib/systemd/system/$service.service"
+ add_symlink "/usr/lib/systemd/system/sysinit.target.wants/$service.service" "../$service.service"
+ done
+ for target in sysinit sockets basic local-fs local-fs-pre remote-fs remote-fs-pre initrd-switch-root; do
+ add_file "/usr/lib/systemd/system/$target.target"
+ done
+
+ # wtf?
+ add_file "/etc/passwd"
+ add_file "/etc/shadow"
+ add_file "/etc/group"
+ add_file "/etc/gshadow"
+ add_file "/etc/nsswitch.conf"
+ # (wtf?)^2
+ add_file "/lib/libnsl-2.16.so"
+ add_symlink "/lib/libnsl.so" "libnsl.so.1"
+ add_symlink "/lib/libnsl.so.1" "libnsl-2.16.so"
+ add_file "/lib/libnss_files-2.16.so"
+ add_symlink "/lib/libnss_files.so" "libnss_files.so.2"
+ add_symlink "/lib/libnss_files.so.2" "libnss_files-2.16.so"
+
+
+ add_file "/usr/lib/systemd/system/systemd-fsck@.service"
+ add_file "/usr/lib/systemd/system/initrd-switch-root.service"
+ add_symlink "/usr/lib/systemd/system/initrd-switch-root.target.wants/initrd-switch-root.service" "../initrd-switch-root.service"
+ add_file "/usr/lib/systemd/system/initrd-pre-switch-root.service"
+ add_symlink "/usr/lib/systemd/system/basic.target.wants/initrd-pre-switch-root.service" "../initrd-pre-switch-root.service"
+
+ add_symlink "/usr/lib/systemd/system/default.target" "basic.target"
+
+ # this should be done by a generator (based on /proc/cmdline), and not be hardcoded for my machine...
+ add_file "/usr/lib/systemd/system/new_root.mount"
+ add_symlink "/usr/lib/systemd/system/local-fs.target.wants/new_root.mount" "../new_root.mount"
+}
+
+help() {
+ cat <