Wednesday, June 17, 2009

Easily Removing VCS resources From A Running Configuration On Unix Or Linux

Hey there,

Today's post is going to be a bit brief (which is a relative statement. If you've never been here before, this post may seem incredibly long ;). The subject matter (as noted in the Subject ;) deals with how to easily, and safely, remove resources from a running VCS (Veritas Cluster Server) configuration. And, just as a matter of course, I feel I must qualify the previous statement by noting that if you remove a vital resource from your running VCS configuration, no matter how safely and correctly you do it, you may end up with a major headache ;) (Please see our other posts on VCS for Linux or Unix if any part of this run-down requires further explanation. Hopefully, we've already covered it :)

And here we go. The method to doing this is so simple, I will be writing the rest of this post in "Dick and Jane" style. See VCS configuration. See VCS configuration running. See Sysadmin. See Sysadmin answer 15 Instant Messages and respond to 3 emails while fielding questions on a conference call... No. That won't work ;)

Here we go, for real. Removing VCS resources from a running VCS configuration can be extremely simple. In fact, in order to make sure that you not only do it simply, but also correctly, you're going to make use of a file that VCS creates automatically when you save your main.cf file. That file is called "main.cmd" The "main.cmd" file should exist already, but if there's any reason you have to doubt that your main.cmd is correct (or you just don't have one - it should be located in /etc/VRTSvcs/conf/config), you can always create one from the running configuration by doing the following with the "hacf" command (I do this, usually, just to be sure):

host # cp /etc/VRTSvcs/conf/config/main.cf /var/tmp/main.cf
host # hacf -cftocmd /var/tmp


The above sequence of commands will create a file named "main.cmd" in your /var/tmp directory. This file contains every single command line (from the most basic to the most specific) that you would need to completely recreate your VCS configuration (of course, using the "-cmdtocf" flag might be a bit easier ;) As such, you can, of course, also use this file as a guide to easily "add" resources to your running VCS config, but that's beyond the scope of this post. "hacf" also allows you to use the "-dest" option so you can put the main.cmd that you created in a separate location, like so:

host # hacf -cftocmd /var/tmp -dest /home/user1/.

And here's where it gets easy :)

Let's say that you wanted to remove a Veritas disk volume from your running VCS configuration (which would, also, usually mean that you would want to remove the mount point from VCS control and remove any dependencies). Assuming that you know the volume's name, you can find out everything you need to know about the volume and the mountpoint, including dependency linkage, by simply using the "grep" command against your main.cmd file (Note that, even if you don't know your volume's name, you can figure that out just as easily by simply grepping for "Volume" - the VCS resource type, which is case sensitive - in your main.cmd file, and looking for the name of the disk volume that way).

Then let's say that your volume's name is VOL_volume54_host. And let's also say that you have the privilege and means to execute the VCS commands you'll be discovering (I'm heavily fighting a strong Airplane joke urge right now ;)

host # grep VOL_volume54 /var/tmp/main.cmd
hares -add VOL_volume54_host Volume SG_host
hares -modify VOL_volume54_host Critical 0
hares -modify VOL_volume54_host Volume volume54
hares -modify VOL_volume54_host DiskGroup hostdg
hares -modify VOL_volume54_host Enabled 1
hares -link MNT_mount54_host VOL_volume54_host
hares -link VOL_volume54_host DG_hostdg_host


For now, we'll just use this information to find the disk mount (Mount) name and grep for that, as well:

host # grep MNT_mount54_host /var/tmp/main.cmd
hares -add MNT_mount54_host Mount SG_host
hares -modify MNT_mount54_host Critical 0
hares -modify MNT_mount54_host MountPoint "/disk54/files"
hares -modify MNT_mount54_host BlockDevice "/dev/vx/dsk/hostdg/volume54"
hares -modify MNT_mount54_host FSType vxfs
hares -modify MNT_mount54_host MountOpt largefiles
hares -modify MNT_mount54_host FsckOpt "%-y"
hares -modify MNT_mount54_host CkptUmount 1
hares -modify MNT_mount54_host SecondLevelMonitor 0
hares -modify MNT_mount54_host SecondLevelTimeout 30
hares -modify MNT_mount54_host Enabled 1
hares -link MNT_mount54_host VOL_volume54_host
hares -link RANDOMRESOURCE_resourcename_host MNT_mount54_host


Now you'll put these all together in order (I prefer to remove link dependencies first, then remove the mount followed by the volume - doing otherwise may cause problems for you). Note that one dependency link showed up in both greps. You can run the same command twice without doing any harm, but I'm stripping the duplicate out for neatness' sake. You're almost ready to go. At this point, you'll end up with this list of VCS commands (which you shouldn't run, but - if you do, accidentally - won't cause any harm):

hares -link MNT_mount54_host VOL_volume54_host
hares -link VOL_volume54_host DG_hostdg_host
hares -link RANDOMRESOURCE_resourcename_host MNT_mount54_host
hares -add MNT_mount54_host Mount SG_host
hares -modify MNT_mount54_host Critical 0
hares -modify MNT_mount54_host MountPoint "/disk54/files"
hares -modify MNT_mount54_host BlockDevice "/dev/vx/dsk/hostdg/volume54"
hares -modify MNT_mount54_host FSType vxfs
hares -modify MNT_mount54_host MountOpt largefiles
hares -modify MNT_mount54_host FsckOpt "%-y"
hares -modify MNT_mount54_host CkptUmount 1
hares -modify MNT_mount54_host SecondLevelMonitor 0
hares -modify MNT_mount54_host SecondLevelTimeout 30
hares -modify MNT_mount54_host Enabled 1
hares -add VOL_volume54_host Volume SG_host
hares -modify VOL_volume54_host Critical 0
hares -modify VOL_volume54_host Volume volume54
hares -modify VOL_volume54_host DiskGroup hostdg
hares -modify VOL_volume54_host Enabled 1


Now, you'll strip this down and "reverse" the commands. And by "reverse" I mean reverse the intent, and not the order ;) So, all -link options will become -unlink options, etc. This will leave you with the following (we're removing every "unnecessary" command, since, for instance, removing a volume automatically removes all of its attributes):

hares -unlink MNT_mount54_host VOL_volume54_host
hares -unlink VOL_volume54_host DG_hostdg_host
hares -unlink RANDOMRESOURCE_resourcename_host MNT_mount54_host
hares -delete MNT_mount54_host
hares -delete VOL_volume54_host


and that's a much shorter, and much nicer, list. Now all you have to do to remove the resources successfully is to do the following (Also, consider that you may want to shut down VCS on all but the primary node, if possible, so that your new configuration doesn't get overwritten, and that all your secondary, tertiary, etc, VCS nodes do a remote build of the new configuration from your primary node):

host # haconf -makerw
host # hares -unlink MNT_mount54_host VOL_volume54_host
host # hares -unlink VOL_volume54_host DG_hostdg_host
host # hares -unlink RANDOMRESOURCE_resourcename_host MNT_mount54_host
host # hares -delete MNT_mount54_host
host # hares -delete VOL_volume54_host
host # haconf -dump -makero


And you're all set. Easy Peasy :)

Cheers,

, Mike


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