ThinClientFasterStartup

Differences between revisions 17 and 18
Revision 17 as of 2006-01-03 22:38:00
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Editor: studiocity-motorola-bsr1-70-36-194-85
Comment: approver comments
Revision 18 as of 2006-02-02 09:37:57
Size: 4294
Editor: 82
Comment: final fixes
Deletions are marked like this. Additions are marked like this.
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 * Add code to ltsp-build-client that processes this list with update-rc.d remove.

'''MattZimmerman: update-rc.d won't do the right thing; the links will be restored if the chroot is upgraded. To permanently disable a service in the chroot, only the start symlinks should be removed. Also, services which may or may not be needed, depending on lts.conf, need to be handled during the boot process, not by ltsp-build-client.'''

 * Make ltsp-client export LTSP_CLIENT and make sure ntpd and syslogd are started after ltsp-client
  * Make changes to the initscripts of syslogd and ntpdate to die immediately if LTSP_CLIENT is set, but NTP_SERVER/SYSLOG_HOST is not set.
 * Make ltsp-client respect NTP_SERVER as well as SYSLOG_HOST (the latter is already implemented in pere's branch)
 * Add code to ltsp-build-client that processes this list, removes the symlinks in rc2.d and sets the S symlinks in rcS.d to K (symlinks are only not restored on upgrade for a runlevel if there still exist any in other runlevels (or if they changed to K for the rcS ones which have no equivalent in other levels)).
 * Make ltsp-client respect NTP_SERVER as well as SYSLOG_HOST if these are set in lts.conf and start the services accordingly (the latter is already implemented in pere's branch)

Summary

Speed up the Thin Client bootprocess for LTSP

Rationale

Ubuntu 5.10 thin clients take ages to boot. Some of the generic startup time improvements will also apply to thin clients, but we should specifically optimize the thin client startup process as well. Thin clients are usually low-spec hardware and need this more than most.

Use cases

Matthew gives a class on usability at university where he uses LTSP in his class, if he's the first in the class for the day he expects his pupils to be able to work immediately after switching on the Thin clients.

Scope

The boot process of LTSP Thin Clients as well as the default bootstrapping of the thin client chroot environment.

Design

  • Rip out the unneeded services from Thin Clients
  • Fix the delay of nfs mounting in klibc (this seems to be a bug that needs to be tracked)
  • Compare the list of started services between LTSP 4.1 and breezy LTSP
  • Remove the "sleep 3" from the initramfs nfs script (it was for debugging the above klibc timeout and was forgotten to be removed somehow)
  • Start LDM as early as possible in the bootprocess (running it as first service in rc2.d is possible)
  • Find the slowing down part in syslogd (strace) and fix it or remove syslogd completely from the thin client startup unless the user configures a SYSLOG_HOST in lts.conf.
  • Disable ntpdate at boot unless the user explicitly configures an NTP_SERVER in lts.conf, disable the clock in ldm.

Implementation

Cutting down the list of started services in rcS.d on the Thin Client to the following gains us 30 seconds:

  • S02mountvirtfs
  • S04udev
    • (according to UdevRoadmap both being moved to initramfs and being replaced with a "catchup")

  • S32ltsp-client-setup
  • S40hotplug
    • (being removed, replaced by initial boot)
  • S40networking (for spoof protection etc)
  • S50alsa-utils (needed for sound)
  • S70xorg-common

This seems to be the bare minimum of bootscripts. The boot process still needs ~60 seconds from hitting the power button (which includes BIOS indeed) to being able to log in at the login manager (which is about as much as a normal ubuntu workstation installation), mostly caused by initramfs and hotplug which should be sped up by changes Scott will make to the initramfs/hotplug architecture (see UdevRoadmap).

Sadly one slowdown that wont be avoidable is the xorg autodetection, probing the devices takes between 20 and 30 seconds depending on the feedback speed of the hardware.

Code

Changes in ltsp-build-client are required to remove the unneeded startup scripts:

  • Make a ltsp-services-blacklist file with a list of installed but unneeded services that get installed by default by debootstrap (we should keep the apps around to be able to enable them if needed, see syslogd and ntpdate below as examples).
  • Add code to ltsp-build-client that processes this list, removes the symlinks in rc2.d and sets the S symlinks in rcS.d to K (symlinks are only not restored on upgrade for a runlevel if there still exist any in other runlevels (or if they changed to K for the rcS ones which have no equivalent in other levels)).
  • Make ltsp-client respect NTP_SERVER as well as SYSLOG_HOST if these are set in lts.conf and start the services accordingly (the latter is already implemented in pere's branch)

The initramfs and hotplug changes are covered in other specs. The ltsp-client startscript should move up to the top of rc2.d (S10ltsp-client).

Outstanding issues during development

Examine the initramfs/hotplug speedup that can be done.

Examine the gain of the inclusion of readahead-list in the bootprocess (for dapper+1, not explicitly part of this spec).

Examining debootstrap for things that dont need to be installed (having a ltsp mode for debootstrap)


CategorySpec

ThinClientFasterStartup (last edited 2008-08-06 16:28:01 by localhost)