On Mon, Dec 1, 2008 at 3:20 PM, Robert Thurlow <robert.thurlow at sun.com>
wrote:
> Mike Gerdts wrote:
>
>> I can not think of a case where "umountall -Z ... " is an advisable
>> command
>
> I don't know of a reason an admin would use it manually,
> but I think it's important to be able to use this in the
> system shutdown path, for reasons previously stated.
>
> Rob T
The way that umountall is in the system shutdown path is what led this
to being something worth fixing. Here's more of the story.
Historically ypstop(1M) and ypstart(1M) have been acceptable
mechanisms used to force a complete restart of NIS-related processes.
To the best of my knowledge, there is no other documented mechanism
prior to Solaris 10. Solaris 10 and later still document these and
carry no scary warnings about side effects. As such, if a system
administrator at a large organization were to decide to restart NIS
processes across various releases of Solaris, "ypstop ; ypstart" would
seem to be a reasonable thing to do. Else, complicated logic is
involved to call svcadm on some releases and the traditional commands
on others.
Beginning with Solaris 10, ypstart and ypstop include:
/usr/sbin/svcadm restart milestone/name-services
Which seems safe enough... except:
$ svcprop nfs/client | grep restart_on
network/restart_on astring error
nlockmgr/restart_on astring error
cbd/restart_on astring error
mapid/restart_on astring error
rpcbind/restart_on astring restart
keyserv/restart_on astring none
gss/restart_on astring none
name-services/restart_on astring refresh
This causes nfs/client to restart when ypstop or ypstart is run. When
nfs/client stops:
$ svcprop nfs/client | grep stop/exec
stop/exec astring /lib/svc/method/nfs-client\ %m
$ grep umountall /lib/svc/method/nfs-client
/sbin/umountall -F cachefs
/sbin/umountall -F nfs
When "/sbin/umountall -F nfs" runs in the global zone, it unmounts NFS
file systems in all non-global zones. The global zone is fixed up
when "/sbin/mountall -F nfs" is run immediately after. Unfortunately,
"mountall -F nfs" does not similarly reach into non-global zones and
as such all non-global zones remain broken.
The same scenario exists for autofs.
Now, getting back to the system shutdown doing the right thing with
trying to clean up from bugs in the zone shutdown process.... Clearly
the current implementation has serious implications for a properly
behaving system that just had its NIS client reconfigured. If
umountall needs to be run such that it takes action on all zones, it
must not be triggered by a restart of name services. On the same
token, disabling the nfs/client service in the global zone should not
have an effect on the running state of non-global zones.
--
Mike Gerdts
http://mgerdts.blogspot.com/
