remove the automatic restart by zoneinit

[yangwu-briphant]

hi,
In order to shorten the time to create a virtual machine，If I remove the automatic restart by zoneinit,
will it have a serious impact ?

Looking forward to your reply, thanks!

[mamash]

As explained on the mailing list already, the original reason for the final reboot was to perform it as an ultimate test of a properly created VM. The first ever VM image used by Joyent on SmartOS (actually those were Solaris Express Nevada builds in the beginning) was a multipurpose one, with services like Apache and Postfix preinstalled and running out of the box, and with the early generation of tooling implemented, things sometimes got "interesting" and a reboot was a good enough final proof.

This is how provisioning currently works with regard to zoneinit:

1. vmadmd prepares the VM filesystem and creates the /var/svc/provisioning file
   2 zoneinit creates the /tmp/.FIRST_REBOOT_NOT_YET_COMPLETE barrier file
2. zoneinit enables the mdata:fetch service, which doesn't fire yet, having an exclude dependency on /tmp/.FIRST_REBOOT_NOT_YET_COMPLETE
3. zoneinit runs its default (and whatever user added) include scripts and schedules a reboot
4. VM reboots (with /tmp/.FIRST_REBOOT_NOT_YET_COMPLETE file now gone)
5. mdata:fetch starts and enables mdata:execute
6. mdata:execute renames /var/svc/provisioning to /var/svc/provision_success
7. vmadmd recognizes the success flag and proclaims the VM provisioned

The thing to note here is that the mdata:fetch script actually processes a lot of system config files (especially networking files in /etc) and right now it runs after the reboot (together with the user and operator scripts, if any), after zoneinit is no longer active or involved in any way.

The reboot still makes sense in some cases, when zoneinit is used to perform more complex tasks, but this can be implemented by the user just by modifying 999-cleanup.sh or dropping in a separate final include file (e.g. 'reboot.sh').

Further testing involved here.

[mamash]

Here's a basic patch that removes the reboot and makes the provision finish immediately. This means that mdata-fetch runs right after zoneinit is done, and mdata-execute runs the user and operator scripts (if any).

(Briefly tested on a minimal-32-16.2.0 image.)

--- /var/zoneinit/includes/999-cleanup.sh
+++ /var/zoneinit/includes/999-cleanup.sh
@@ -6,5 +6,6 @@ svccfg -s zoneinit 'setprop application/done = true'
 svcadm refresh zoneinit
 rm -f ${ZONECONFIG}

-log "scheduling an immediate reboot"
-echo "reboot >/dev/null" | at now >/dev/null
+log "clearing first boot barrier, letting mdata finish the provision"
+rm -f /tmp/.FIRST_REBOOT_NOT_YET_COMPLETE
+svcadm refresh mdata:fetch

[joshwilsdon]

I'd just add here that doing what @mamash suggested may leave you with some problems using tools like who and w and last and uptime until you've rebooted because the /var/adm/utmpx and /var/adm/wtmpx are expected to be recreated after the reboot. That may or may not be important to you.

If the goal is only faster creation, another option is to use the joyent-minimal brand which skips zoneinit entirely.