Configurable Hostids for Non-Global Zones [PSARC/2008/647 FastTrack, timeout 10/30/2008]

[Jordan Vaughan]

Ric Aleshire wrote:
>>
>> Both native- and sn1-branded zones will be capable of emulating hostids.
>> However, lx-branded zones will forbid hostid emulation because supported
>> Linux distributions (e.g., CentOS) retrieve hostids from /etc/hostid 
>> rather
>> than kernel memory (as in Solaris OS).  Zone administrators desiring 
>> to change
>> an lx-branded zone's hostid can modify the zone's /etc/hostid file.
>>
>> Solaris 10 users will be able to configure a Solaris 8 or 9 
>> container's hostid
>> through the already-existing "add attr hostid" interface and new 
>> hostid property
>> interface in zonecfg(1M).
>>   
> 
> Can you clarify how this applies to other brands?  It sounds like only 
> lx is specifically prohibited from using these
> hostid interfaces.  How about other brands, such as the cluster brand 
> and possible future native-based brands?
> 
> -Ric

Ric,

As long as sysinfo(SI_HW_SERIAL) system calls originating from within a 
branded zone are handled by the native Solaris kernel, the zone will be 
capable of emulating a hostid.  All native-based brands will drop into 
the native kernel when sysinfo(SI_HW_SERIAL) system calls are made, so 
all native-based brands will be capable of emulating hostids.  From what 
I have heard, cluster-branded zones are essentially native-branded zones 
with special callbacks, so cluster-branded zones will be capable of 
emulating hostids.

Cluster-branded zones serve as an excellent example of the usefulness of 
non-global zone hostid emulation.  Each cluster-branded zone could 
emulate a hostid.  If clustering software migrates a cluster-branded 
zone between physical cluster nodes, then if the zone's configuration is 
preserved during the migration, then the zone's emulated hostid will be 
the same no matter which physical node hosts it.  Without non-global 
zone hostid emulation, a cluster-branded zone's hostid can change when 
the zone migrates, potentially impacting how software within the zone 
will function.

Regards,
Jordan