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While only the newer Sun systems and higher-end PCs today are equipped with DVD drives, application software is beginning to arrive on DVDs because of the tremendous increase in storage capacity. Your typical CD holds about 700 MB of data. That was a lot of data when system disks were only a couple of gigabytes in size. DVDs, on the other hand, may hold 4.3 or 4.7 GB -- and that's just a starting point. If the multi-layer storage capacity of DVDs is ever fully employed, DVDs will hold nearly 16 GB of data. With less overhead for data integrity and more area, it's no wonder that Solaris is being shipped on DVDs only.
So what do you do if you need to install software that is only available on a DVD on a system which has only a CD drive? One answer is to mount and share the DVD from a system with a DVD reader. Since I had to do that just last week, I'll run through the steps in today's column.
First, to share a DVD, you must insert it into a system that can read it. Sharing a DVD is essentially the same as sharing a CD. In fact, DVDs will automount under the same mount point as CDROMs, /cdrom, if vold is running on a Solaris system.
bash# ls /cdrom
big_app_install cdrom0
To share the mounted drive, we use the share command. Notice we share the directory containing the data, not the /cdrom mount point:
bash# share -o ro -d base_ade_netra /cdrom/base_ade_netra
I've used the read-only option (-o ro) and the description option (-d
) to share the DVD above. And I always check a file system after I've shared it to see that my sharing has worked:
bash# share
- /cdrom/big_app_install ro "big app install"
To mount the drive on the target system, I use the mount command. If you run into a "program not registered" error like that shown below, your NFS server is not running the NFS processes. If so, you can start them with the S15nfs.server script but, unless your /etc/dfs/dfstab file contains share entries, you will run into a second error, also shown below.
bash# mount -o ro fserver:/cdrom /cdrom
nfs mount: fserver: : RPC: Program not registered
nfs mount: retrying: /cdrom
# ./S15nfs.server start
NFS service was not started because /etc/dfs/dfstab has no entries.
When your /etc/dfs/dfstab file contains at least one share command, you can start NFS services and then verify that your file systems were shared.
bash# ./S15nfs.server start
bash# share
- /cdrom/big_app_install ro "big_app_install"
To mount the file system on your file server, use the mount command along with the read-only option. You can mount using the /mnt directory or create a /dvd directory if that makes more sense for you.
bash# mount -o ro fserver:/cdrom/big_app_install /mnt
When you have extracted or otherwise finished with the data on your mounted DVD, you should unmount the drive on the client before attempting to eject it on the file server.
bash# umount /mnt
If you won't be mounting the same DVD again, you may want to remove the sharing command from the server and then unmount the drive. If you are depending on the services of vold, you can unmount the DVD using just the eject command. If you manually mounted the DVD, you should manually unmount it as well.
bash# unshare /cdrom/big_app_install
bash# eject
The move from CDs as the standard for software installation to DVDs may take a while, but it's as predictable as the move from diskettes to CDs that occurred many years ago and for the same reason. The capacity of double-sided diskettes was only 1.44 MB. The 700 MB CD ROMs hold more than 650 times as much data and are comparably priced.
DVDs have roughly six times the capacity of CD ROMs and are not significantly more expensive. When you consider how much time is saved if you can install from one platter instead of six, the future is clear. CD ROM drives that are *only* CD ROM drives and not also DVD readers are on their way out.
