AIX > Tips & Techniques > Miscellaneous

Mastering Soft and Hard Shutdowns

There was a time when computers were shut down once a week, “just to clear out the cobwebs.” Someone might have to be in the office early on a Monday to hit the power or reset button and hope the system would come back up again. Today, system shutdowns are much less common. We have high expectations of system uptime. It’s not unusual to find servers that have never been powered down, even a year or two after they were first installed.

With the reliability, availability and serviceability features of IBM Power Systems, you may never get to see a physical host shut down and powered off.

However, you may need occasionally to shut down a logical partition (LPAR) – also known as a virtual server. This might happen:

• After an OS upgrade on the partition
• As part of a disruptive firmware upgrade on the managed system
• In the rare event of the OS crashing

There are a few points to keep in mind when you're planning to shut down a partition.

Plan for Uptime

First of all, ask yourself whether you need to bring the system down at all. You might not have to. Many changes can be done without any OS outage. On AIX, some software can be installed without requiring a system reboot. AIX lets you increase paging space, change the sizes of file systems and even expand the rootvg disk on the fly.

So you might not need that shutdown after all. But if you do, it's easy and generally quick.

Just a Minute!

You can shut down the AIX OS with the shutdown command. If you don’t use any flags, there is a message sent to all users logged in, and they are given a one-minute warning before the shutdown process continues.

root@nim/ # shutdown

SHUTDOWN PROGRAM
Thu Oct 13 12:00:12 EST 2011

Broadcast message from root@nim (tty) at 12:00:12 ...

shutdown: PLEASE LOG OFF NOW !!!
All processes will be killed in 1 minute.

That minute of grace is sometimes worth the wait. It allows you to kill or cancel the shutdown process, which is good if you suddenly remember something you need to change or check before shutting down your partition—or if you discover you were logged onto the wrong partition. A couple of things to keep in mind are:

• The warning will only go to users who have a UNIX login session. If they are connected via an application or a client, they might not find out about the outage until they lose their connection.
• Running the shutdown command will kill all processes. Generally you'll want to do that gracefully, using scripts or utilities, which will close off applications and stop databases neatly.

You can do a fast shutdown by using the -F flag. This will skip the one-minute grace period. That's faster, of course, but it doesn’t let you kill your shutdown command. With shutdown -F there's no turning back.

Tweet