dec2004.tar

Automatically Mirroring the Boot Disk with Custom JumpStart

Matthew Cheek

One of the unsung heroes of the Solaris Operating Environment (OE) is the Custom JumpStart facility. This powerful framework permits a Solaris systems administrator to automatically install or upgrade multiple systems based on pre-defined Profiles. This is especially valuable in environments with many, similarly (or identically) configured servers as it can result in absolute consistency across machines. Once the JumpStart server components are properly provisioned, a completely automated, hands-free Solaris installation is possible. In addition to automating the basics of a Solaris installation, such as partitioning disks, selecting software groups, and configuring network interfaces, Custom JumpStart also provides for the execution of pre-installation and post-installation scripts, which permits absolute customization of the install process.

Due to a requirement to quickly and consistently install and deploy many dozens of similar servers, we implemented a Custom JumpStart environment and developed a suite of custom post-installation (or Finish) scripts to complete local customization, such as installing additional packages and patches, configuring the automounter, disable unnecessary services, etc. Because our standard configuration is a mirrored boot disk using Solaris Volume Manager, we also wanted a solution for automating this via the Custom JumpStart framework. Unfortunately, Custom JumpStart for Solaris 9 12/03 or earlier does not natively support the automatic mirroring of a system's boot disk with the Solaris Volume Manager as part of a Custom JumpStart installation. Thus, further manual administrative work was necessary at the conclusion of the Custom JumpStart installation to implement a mirrored boot configuration. Ultimately, a Custom JumpStart Finish script was developed for this purpose.

Sun finally recognized this longstanding deficiency and, with the release of Solaris 9 4/04 (Update 6), Custom JumpStart now supports automatic creation of mirrored filesystems using the Solaris Volume Manager during a Custom JumpStart installation.

This article will introduce and describe this new Custom JumpStart feature. It is assumed that the reader is already familiar with the configuration, provisioning, and use of a Custom JumpStart environment. In the May 2000 issue of Sys Admin, Peter van der Weerd's article "Building a JumpStart Server for Solaris" (http://www.samag.com/documents/s=1165/sam0005a/) provided an excellent introduction to JumpStart for the uninitiated. For more detailed coverage, see the References at the end of the article or review the Installation Guide for your specific Solaris release. Solaris 9 on SPARC will be the subject OE for this discussion, but Solaris x86 OE is also applicable.

Finally, for those environments still using versions of Solaris earlier than Solaris 9 4/04, our previously developed Custom JumpStart Finish script to automatically mirror the boot disk using SVM will be presented. Extending this script for Veritas Volume Manager (VxVM) boot disk mirroring will be left as an exercise to the reader.

Automatic Mirroring with Custom JumpStart Profiles

Sun added support for automatically mirroring filesystems during a Custom JumpStart installation by extending the Custom JumpStart Profile mechanism. More specifically, there is a brand new metadb Profile keyword and the filesys Profile keyword was enhanced to permit the system administrator to specify the location of the required SVM state database replicas and which filesystems to mirror.

Consider this straightforward example Custom JumpStart Profile:

# profile keyword       profile value(s)
# ---------------       ----------------
  install_type          initial_install
  system_type           server
  cluster               SUNWCall
  partitioning          explicit
  filesys               c0t0d0s0 free /
  filesys               c0t0d0s1 512 swap
  filesys               c0t0d0s3 1024 /var

This profile will result in the initial server installation of the entire distribution of the Solaris OE using the first disk on the first (or only) SCSI channel as the boot disk. Further, the boot disk will be explicitly partitioned with a 512-MB swap partition, a 1024-MB /var partition, and all the remaining space assigned to the root partition. The two resulting partitions (i.e., / and /var) will be the standard Solaris UFS filesystem and not be mirrored automatically, regardless of whether there are other suitable disks in the system. When the following two commands are run on a system installed from this example profile, the result is obvious:

# df -F ufs -k
Filesystem          kbytes    used   avail    capacity  Mounted on
/dev/dsk/c0t0d0s0   15847503  756024 14933004   5%      /
/dev/dsk/c0t0d0s3   1018191   7183   949917     1%      /var

# swap -l
swapfile            dev     swaplo blocks   free
/dev/dsk/c0t0d0s1   32,1     16 1050752    1050752

Before Solaris 9 4/04, it would then be necessary for the administrator to manually configure SVM to complete any desired mirroring including the additional requisite reboot to mirror the root partition. (Alternatively, the Custom JumpStart Finish script presented later in this article could be used to automatically mirror filesystems.)

Simply by making a few modifications to our example Profile, however, Custom JumpStart on Solaris 9 4/04 and later will automatically mirror our filesystems:

# profile keyword       profile value(s)
# ---------------       ----------------
  install_type          initial_install
  system_type           server
  cluster               SUNWCall
  partitioning          explicit
  filesys               mirror c0t0d0s0 c0t1d0s0 free /
  filesys               mirror c0t0d0s1 c0t1d0s1 512 swap
  filesys               mirror c0t0d0s3 c0t1d0s3 1024 /var
  metadb                c0t0d0s7
  metadb                c0t1d0s7

This profile will do exactly the same as before, but with the additional entries the resulting system will have all three partitions (the / and /var filesystems and the swap partition) mirrored with SVM. Additionally, the required SVM state database replicas will be placed on slice seven of the specified disks. To show the results of this profile, the following commands are run:

# df -F ufs -k
Filesystem           kbytes    used   avail   capacity  Mounted on
/dev/md/dsk/d6       15847503  756001 14933027    5%    /
/dev/md/dsk/d3       1018191   7177   949923      1%    /var

# swap -l
swapfile             dev     swaplo  blocks   free
/dev/md/dsk/d0       85,0      16    1050752  1050752

# metastat -p
d6 -m d7 d8 1
d7 1 1 c0t0d0s0
d8 1 1 c0t1d0s0
d3 -m d4 d5 1
d4 1 1 c0t0d0s3
d5 1 1 c0t1d0s3
d0 -m d1 d2 1
d1 1 1 c0t0d0s1
d2 1 1 c0t1d0s1

# metadb
        flags           first blk     block count
     a m  p  luo        16            8192     /dev/dsk/c0t0d0s7
     a    p  luo        8208          8192     /dev/dsk/c0t0d0s7
     a    p  luo        16400         8192     /dev/dsk/c0t0d0s7
     a    p  luo        16            8192     /dev/dsk/c0t1d0s7
     a    p  luo        8208          8192     /dev/dsk/c0t1d0s7
     a    p  luo        16400         8192     /dev/dsk/c0t1d0s7

These filesys and metadb Profile keyword/value examples demonstrate their minimum form. Both keywords have additional, optional parameters that provide greater configurability to the administrator. For instance, in the previous example profile, Custom JumpStart automatically assigned SVM metadevice names to the mirrors and sub-mirrors starting with d0 and incrementing sequentially. This is the default behavior and, in many cases, may be acceptable. However, it may be desirable to name the mirrors explicitly and the following profile fragment demonstrates how:

filesys               mirror:d10 c0t0d0s0 c0t1d0s0 free /
filesys               mirror:d20 c0t0d0s1 c0t1d0s1 512 swap
filesys               mirror:d30 c0t0d0s3 c0t1d0s3 1024 /var

This profile will name the /, swap, and /var SVM mirror metadevices d10, d20, and d30, respectively. Unfortunately, Custom JumpStart does not provide the ability to explicitly name the sub-mirrors and their names will be automatically assigned as before, starting with the first unused d- number (in this case, d0). The resulting configuration will be:

# metastat -p
d10 -m d7 d8 1
d7 1 1 c0t0d0s0
d8 1 1 c0t1d0s0
d30 -m d4 d5 1
d4 1 1 c0t0d0s3
d5 1 1 c0t1d0s3
d20 -m d1 d2 1
d1 1 1 c0t0d0s1
d2 1 1 c0t1d0s1

Furthermore, without specifying any optional parameters, the metdb profile keyword creates three SVM replicas that are 4 MB in size. If fewer (or more) replicas and/or a different size are desired, use a metadb command similar to the following:

metadb                c0t0d0s7 size 16384 count 5

This will create five replicas on an 8-MB slice 7. (The size value is specified in 512-byte disk blocks.)

Note that Custom JumpStart only permits the creation of SVM single-slice concatenations (RAID 0) and mirrors of single-slice concatenations (RAID 1). Creation of other SVM objects via Custom JumpStart -- such as multiple-slice concatenations (Stripes) and RAID5 volumes -- are not supported.

As a final example, here is a more complex profile:

# profile keyword    profile value(s)
# ---------------    ----------------
  install_type       initial_install
  system_type        server
  cluster            SUNWCprog
  partitioning       explicit
  metadb             c0t0d0s7 size 16384 count 4
  metadb             c0t1d0s7 size 16384 count 4
  filesys            mirror:d10 c0t0d0s0 c0t1d0s0 auto /
  filesys            mirror:d20 c0t0d0s1 c0t1d0s1 512 swap
  filesys            mirror:d30 c0t0d0s3 c0t1d0s3 2048 /usr
  filesys            mirror:d40 c0t0d0s4 c0t1d0s4 1024 /var
  filesys            mirror:d100 c0t0d0s5 c0t1d0s5 free /export/home

This profile will result in an initial server installation of the Solaris developer system support software group. Four replicas each of the SVM state database are created on an 8-MB slice 7 of the specified disks. Additionally, Custom JumpStart will create a mirrored root, swap, /usr, /var, and /export/home partition named d10, d20, d30, d40, and d100, respectively. The swap, /usr, and /var partitions are explicitly sized; the root partition is automatically sized by JumpStart based on the selected software, and all remaining unused space is assigned to the /export/home partition.

Automatic Mirroring with a Custom JumpStart Finish Script

If you are unable to take advantage of the new automatic mirroring features introduced in the Solaris 9 4/04 edition of Custom JumpStart, the only option for automatic mirroring is a Custom JumpStart Finish script. Such a Finish script will automatically execute the steps necessary to implement the desired SVM mirrored configuration. To simplify this Finish script, the strategy we adopted was to define a reference configuration with regard to partitioning, filesystem layout, and SVM layout and then code the script to implement that configuration. Here is a summary of that reference configuration codified in the svm.finish script in Listing 1:

The root filesystem resides on slice 0 of the boot disk.

The swap partition resides on slice 1 of the boot disk.

The /var filesystem resides on slice 3 of the boot disk.

The next available disk is selected as the mirror disk.

Three SVM state database replicas are placed on each slice 7 of the boot and mirror disk.

The boot/system metadevice naming convention is as follows:

Partition	Mirror	Submirrors
root	d10	d11, d12
primary swap	d20	d21, d22
var	d30	d31, d32

The use of this Finish script depends on a properly configured Profile and rules file plus several additional rules file entries. Assuming the target client is a Sun Enterprise 250 server with a pair of internal disks, our previously introduced example profile is suitable:

# Profile Name: e250.profile
#
# profile keyword       profile value(s)
# ---------------       ----------------
  install_type          initial_install
  system_type           server
  cluster               SUNWCall
  partitioning          explicit
  filesys               c0t0d0s0 free /
  filesys               c0t0d0s1 512 swap
  filesys               c0t0d0s3 1024 /var
  filesys               c0t0d0s7 16

Notice that we must explicitly reserve slice 7 for the SVM state database replicas. By not specifying a filesystem mount point or type for this slice, the partition is defined as a raw slice without a filesystem.

The associated Custom JumpStart rules entry for the above example is:

model SUNW,Ultra-250 - e250.profile svm.finish

In addition to specifying the Finish script in the entry, it is necessary to add the following probe commands to the beginning of the rules file:

probe disks
probe rootdisk

Once these Custom JumpStart files are provisioned on the JumpStart server and the Finish script is in place, add the install client with the add_install_client command and start the Custom JumpStart installation. After completing the normal Custom JumpStart installation process, our Finish script will be run, which does the following steps:

A set of variables define the slices and SVM metadevice names.
The BOOTDISK variable is assigned with the cWtXdY value of the rootdisk.
The DISKLIST variable is assigned with a space-delimited list of all the disks on the install client.
The first non-rootdisk is selected as the mirrordisk. This script may fail if the selected mirrordisk is smaller than the rootdisk.
A Solaris boot script to do the initial SVM configuration is created using the "here document" technique. This first boot script's purpose is to:
Copy the rootdisk's partition layout to the mirrordisk.
Create three SVM state database replicas on slice 7 of the rootdisk and mirror disk.
Create the SVM submirror and mirror metadevices for swap and /var.
Update the client's vfstab to reflect the new device names.
Create the secondary Solaris boot script to attach the SVM mirrors after the subsequent reboot.
Create and activate the root SVM submirror and mirror metadevices.
Move the script out of the way and reboot.

Summary

This article has presented two methods for automatically mirroring an install client's boot disk via the Sun Solaris Custom JumpStart framework. Later versions of Custom JumpStart natively support this automatic mirroring, albeit with some limitations. Through the use of a custom Finish script, a Solaris systems administrator may completely control the mirror process. In fact, the Finish script presented here works without change within the latest Custom JumpStart version framework.

I hope this article will encourage you to consider the use of Custom JumpStart within your environment, especially as a method of automating Solaris installations. The example Finish script demonstrates some useful scripting techniques that you may be able to apply to Finish scripts of your own.

Legal Statement

This work represents the view of the author and does not necessarily represent the views of the University of Pittsburgh Medical Center. UPMC does not endorse, warrant, or otherwise take responsibility for the contents of this work.

References

John S. Howard and Alex Noordergraaf, JumpStart Technology: Effective Use in the Solaris Operating Environment, Prentice Hall PTR, 2001.

Paul Anthony Kasper and Alan L. McClellan, Automating Solaris Installations: A Custom JumpStart Guide, Prentice Hall PTR, 1995.

Chris Josephes, A Framework for JumpStart Begin/Finish Scripts, Sys Admin Oct 2001 (vol 10, no. 10)

Matthew Cheek is a senior Unix systems administrator with experience in the healthcare, telecommunications, software development, and manufacturing industries and has installed, configured, managed, and written about Unix systems since 1988. He is the lead author of Tru64 UNIX System Administrator's Guide from Digital Press. Matt is currently at the University of Pittsburgh Medical Center (UPMC) in Pittsburgh, Pennsylvania and can be reached at: cheekmp@upmc.edu. He spends his free time with his wife, Sondra, and their three children, Stephanie, Nickolas, and Nathan.