From: Petter Reinholdtsen Date: Sun, 17 Jun 2007 16:32:32 +0000 (+0000) Subject: Final talk. X-Git-Url: http://pere.pagekite.me/gitweb/homepage.git/commitdiff_plain/3171d21fbee575090134e59bd867cd224b3692d4?hp=dacd4f18cfe21e4c965753eb78a28b5e14743242 Final talk. --- diff --git a/mypapers/200706-bootseq/200706-bootseq.html b/mypapers/200706-bootseq/200706-bootseq.html new file mode 100644 index 0000000000..40a6c5d9ae --- /dev/null +++ b/mypapers/200706-bootseq/200706-bootseq.html @@ -0,0 +1,349 @@ + + + + + + + + + + + + +

Dependency based boot sequence

+ +

Reordering the boot sequence for correctness and speed

+ +

There are several boot options available in Debian, and the default + SysV-derived one can be tuned and corrected. The talk will present + the available options, and go into details on some of the pitfalls + and advantages of the default boot system. It will present some + results based on the Google summer of code project working on the + boot system.

+ +

Petter Reinholdtsen +
pere@hungry.com +
Debconf 2007 Edinburgh, 2007-06-17

+ +

About the speaker

+ +

Using Linux since 1993 +
Debian Developer since 2002 + +
Educated at University of Tromsø, Western Australia and Oslo + +
Employed at University of Oslo to develop system administration tools +
Leader of the Norwegian Unix User Group + +
Co-maintaining sysvinit, maintaining insserv +
and a few other (Debian Edu, Debian GIS, Debian + Java, Debian Boot, etc) + +

+ +

Summary of this talk

+ +

Quick overview of the boot system alternatives in Debian +
Some problems with the current system +
How to improve the boot sequence ordering +
how to prepare packages for this +

+ +

Based on work done by Carlos Villegas during Google Summer of Code +2006, available from +http://initscripts-ng.alioth.debian.org/soc2006-bootsystem/.

+ +

Debian include several boot system options

+ +

SysV init is only the most used boot system in Debian, not the only + one.

+ +

file-rc +
upstart +
init-ng +
minit +
runit +
metainit initiative for init.d scripts + +

+ +

The SysV boot system

+ +

Start first all scripts in /etc/rcS.d/ + +
For the runlevel 2, first all K##scripts in /etc/rc2.d/, next all + S##script. + +
All .sh scripts are sourced, the rest are exec-ed + +

+ +

Current sid boot sequence (base install)

+ +

+/etc/rcS.d:
+README                  S30checkfs.sh
+S01glibc.sh             S30procps.sh
+S02hostname.sh          S35mountall.sh
+S02mountkernfs.sh       S36mountall-bootclean.sh
+S04mountdevsubfs.sh     S39ifupdown
+S05bootlogd             S40networking
+S10checkroot.sh         S45mountnfs.sh
+S11hwclock.sh           S46mountnfs-bootclean.sh
+S12mtab.sh              S55bootmisc.sh
+S18ifupdown-clean       S55urandom
+S20module-init-tools    S99stop-bootlogd-single
+S25libdevmapper1.02.1
+
+/etc/rc2.d:
+README                  S89cron
+S10sysklogd             S99rc.local
+S11klogd                S99rmnologin
+S20makedev              S99stop-bootlogd
+S20openbsd-inetd
+

+ +

Current sid shutdown sequence (base install)

+/etc/rc6.d:
+K11cron                 S30urandom
+K20makedev              S31umountnfs.sh
+K20openbsd-inetd        S35networking
+K25hwclock.sh           S36ifupdown
+K89klogd                S40umountfs
+K90sysklogd             S60umountroot
+README                  S90reboot
+S20sendsigs
+

+ +

But is it correct? + +

Problems with the current boot system

+ +

Slightly incorrect ordering during startup and shutdown +
Hard to pick correct sequence number +
The halt/reboot runlevels are inconsistent/confusing (or wrong, + depending on your view) + +
Impossible to parallelise +

+ +

How can we verify the boot sequence correctness?

+ +

Document the dependencies of each script +
Verify the scripts are started in dependency order + +

+ +

Example header:

+ +

+#!/bin/sh -e
+### BEGIN INIT INFO
+# Provides:          networking
+# Required-Start:    mountkernfs ifupdown $local_fs
+# Required-Stop:     ifupdown $local_fs
+# X-Start-Before:    nis
+# X-Stop-After:      nis
+# Default-Start:     S
+# Default-Stop:      0 6
+# Short-Description: Raise network interfaces.
+### END INIT INFO
+

+ +

Verifying the current sequence

+ +

Using these headers and a script from the insserv package, we can +verify the boot order: + +

+# /usr/share/insserv/check-initd-order   -o
+LSB header missing in /etc/rcS.d/S11hwclock.sh
+LSB header missing in /etc/rcS.d/S25libdevmapper1.02.1
+Incorrect order modutils@? > checkfs.sh@30
+Incorrect order $all@? > stop-bootlogd-single@99
+Incorrect order $time@? > sysklogd@10
+Incorrect order $time@? > cron@89
+Incorrect order $all@? > rmnologin@99
+#  
+

+ +

For the packages without dependency information, override files can be +read from /usr/share/insserv/overrides/ and +/etc/insserv/overrides/. + +

Verifying the current sequence II

Current status (base task install), with override files.

+# /usr/share/insserv/check-initd-order
+Incorrect order $local_fs@? > hwclock.sh@11
+Incorrect order $remote_fs@? > hwclock.sh@11
+Incorrect order modutils@? > libdevmapper1.02.1@25
+Incorrect order modutils@? > checkfs.sh@30
+Incorrect order $all@? > stop-bootlogd-single@99
+Incorrect order $all@? > rmnologin@99
+#
+

+ +

Verifying the current sequence III

Current status (desktop task install)

+# /usr/share/insserv/check-initd-order -o
+LSB header missing in /etc/rcS.d/S11hwclock.sh
+LSB header missing in /etc/rcS.d/S25libdevmapper1.02.1
+Incorrect order modutils@? > checkfs.sh@30
+Incorrect order $all@? > stop-bootlogd-single@99
+Incorrect order $time@? > sysklogd@10
+LSB header missing in /etc/rc2.d/S19hplip
+LSB header missing in /etc/rc2.d/S20cupsys
+LSB header missing in /etc/rc2.d/S20hotkey-setup
+LSB header missing in /etc/rc2.d/S89anacron
+Incorrect order $time@? > cron@89
+Incorrect order $all@? > rmnologin@99
+#        
+

+ +

Reordering based on dependency information

+ +

Advantages: + +

No need to replace existing init.d scripts +
Activated by adding headers to the scripts or use override files +
Experimental code to enable it is in the insserv package + +

+ +

How to enable this by default + +

Install the insserv package +
Make all start-symlinks in rc0 and rc6 to stop symlinks +
Replace update-rc.d +
Reorder rc*.d/* +

+ +

Status of dependency based sysv boot sequence

+ +

Majority of common packages provides dependency information +
Correct startup sequence for base and desktop tasks when enabled. +
Fairly correct shutdown sequence. +
Some packages fail to install because of incorrect init.d script + registration order + +

+ +

+To enable: BAD_INSSERV_HACKER=true dpkg-reconfigure insserv +

Testrun: +

+insserv:/var/tmp/chroot-sid-base-reorder# BAD_INSSERV_HACKER=true dpkg-reconfigure i
+info: Backing up existing boot scripts in /var/lib/insserv/bootscripts-20070615T1617.tar.gz
+info: Reordering boot system, log to /var/lib/insserv/run-20070615T1617.log
+info: Recording new boot sequence in /var/lib/insserv/bootscripts-20070615T1617-after.list
+info: Use '/usr/sbin/update-bootsystem-insserv restore' to restore the old boot sequence.
+success: Boot system successfully converted
+Adding `diversion of /usr/sbin/update-rc.d to /usr/sbin/update-rc.d.distrib by insserv'
+#
+

+ +

Similar boot graph

+ +

Reordered sid boot sequence (base install)

+/etc/rcS.d:
+README                  S05mtab.sh
+S01glibc.sh             S06mountall.sh
+S01libdevmapper1.02.1   S07ifupdown
+S02hostname.sh          S07mountall-bootclean.sh
+S02mountkernfs.sh       S07urandom
+S03mountdevsubfs.sh     S08networking
+S03procps.sh            S09mountnfs.sh
+S04bootlogd             S10mountnfs-bootclean.sh
+S04checkroot.sh         S11bootmisc.sh
+S05checkfs.sh           S11hwclock.sh
+S05ifupdown-clean       S11stop-bootlogd-single
+S05module-init-tools
+/etc/rc2.d:
+README                  S11openbsd-inetd
+S07makedev              S11rc.local
+S07sysklogd             S12stop-bootlogd
+S08cron                 S13rmnologin
+S08klogd
+

+ +

Reordered sid shutdown sequence (base install)

+ +

+/etc/rc6.d:
+K03openbsd-inetd        K31umountnfs.sh
+K06cron                 K35networking
+K06klogd                K36ifupdown
+K07sysklogd             K40umountfs
+K20makedev              K60umountroot
+K20sendsigs             K90reboot
+K25hwclock.sh           README
+

+ +

I'm not brave enough, get me out of here

+ +

It is possible to automatically undo the reordering, once, +by reconfiguring insserv and disabling the dependency based boot.

+ +

+# BAD_INSSERV_HACKER=true dpkg-reconfigure i
+info: Disabling dependency based boot system
+Removing `diversion of /usr/sbin/update-rc.d to /usr/sbin/update-rc.d.distrib by insserv'
+info: Restoring using backed up copy of init.d/ and rc*.d/.
+info: successfully restored backup of init.d scripts
+#
+

+ +

How can package maintainers assist

+ +

Update their init.d scripts to include correct dependency + information using the LSB headers defined for this purpose, + http://wiki.debian.org/LSBInitScripts +
Make sure their init.d scripts are registered in dependency order +
Start using insserv to detect bugs in the packages +

+ +

Even running boot scripts in parallel is possible

+ +

echo CONCURRENCY=shell >> /etc/default/rcS

+ + +

Thank you very much

+ +

Questions?

+ +

http://www.hungry.com/~pere/mypapers/200706-bootseq/

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