This chapter describes Dataless Management Services (DMS),
the dataless management utility
(dmu),
the requirements for setting up a
DMS environment, and the relationship between DMS
servers and clients.
In a dataless management services (DMS) environment, a server system
maintains the
root,
/usr,
and
/var
file systems for all client systems. The server
maintains one copy of
root
for each client. The
/usr
file system is exported read only and
is shared by all clients registered to the environment. Client
systems have their own
/var
file system. All swapping and dumping is done on the client's
local disk.
The dataless management utility (dmu) creates a
root
file system based on
the software subsets installed in the
DMS environment area on the server. This
root
file system
is accessed by client systems over a Local Area Network (LAN).
DMS lets system administrators
customize the
root
and
/usr
file systems before client systems access them.
You must have superuser privileges to perform many of the
dmu
functions.
The advantages of installing DMS are:
/usr
area, you eliminate the need for disk space to hold a
separate
/usr
area for each client.
For Alpha systems,
you can save more than 200 megabytes (MB) for each client.
The DMS utility,
dmu,
manages the sharing of installed operating system software between
servers and clients in a LAN.
In addition to the server's normal disk area, one or more disk
partitions are reserved as the DMS area. The DMS area is made up
of one or more product environments and client areas.
In the DMS area, the server maintains multiple copies of the
root
area, one for each client. Each copy is in a client
root
directory in the DMS area and is customized for the client in
order to provide for differences between hardware platforms or
environmental requirements.
Each of the client
root
directories is private;
this means that there is a directory for each client so that no
conflict or confusion exists between clients. The server's DMS
root
and
/usr
areas are made available to clients by means of the Network
File System
(NFS). For more information about the NFS used by
Digital UNIX
systems, refer to the
Network Administration
guide.
Beyond verifying clients' identities, vectoring their boot requests, and providing their system disk space, the server does not interact directly with the clients. The server can, if desired, support local timesharing users and need not be dedicated to DMS.
A DMS client's system disk space (
root
and
/usr
areas) is physically connected to the server instead of to the client.
The client accesses that disk area through a LAN
connection with the server. Each DMS client is booted across the
network from its private
root
area on the server. Once booted, the
client continues to use its
root
files and
/usr
files from the server's DMS area. These files appear to the
client as if they were on local disks, as shown in
Figure 9-1.
As indicated in Figure 9-1, clients must have local disks. In addition to local disks, clients can import file systems from any other computer to which they have network access. Clients use swap and dump space on their local disks.
One or more
DMS environments
can reside in a partition.
If you want to prevent the
dmu
utility from putting all DMS environments in the same disk
partition, indicate a unique mount point for each DMS environment.
The DMS environment disk space requirements should be calculated
using the worksheets in
appendix B.
Then the mount point of
./dmsn.alpha
should be added to
/etc/fstab.
Each DMS environment contains a customized
Digital UNIX
file system
consisting of
root,
/usr,
and
/var.
The
dmu
utility copies
the
root
area to the client area when a client is added
to the dataless environment.
Figure 9-2
shows the
/var/adm/dms
portion of a DMS area,
it contains two DMS environments,
dms0.alpha
and
dms1.alpha.
Each DMS environment contains a
root
and
/usr
file system.
The
root
file system is copied to each client system.
The
/usr
file system is read only and is shared among all client systems
registered to the environment.
The
root
file system contains copies of the kernel,
.vmunix,
vmunix
and other primary system
files. These primary files can be in either
new
form (files supplied in the
Digital UNIX
distribution kit and prefixed with
.new..)
or in
prototype
form (files prefixed with
.proto..).
The
.new..
version of a file should never be customized.
The
.proto..
files have special significance for DMS
environments. By modifying the
.proto..
files, the DMS server system administrators can
customize the system to meet their specific needs.
These customized
.proto..
files are used during the configuration of the
server's DMS client environments.
Standard files (such as
/etc/hosts
and
/etc/fstab
for example)
can be modified so that clients do not have to modify them.
The
/usr
file system contains common files that can be
used without being tailored by
clients registered to the DMS environment.
DMS environments can be created with many different combinations of
products to allow servers to provide diversified service based on
client's software product needs.
For example, you could have a DMS environment with only the base
Digital UNIX
Version 4.0 operating system and another DMS environment
with the
Digital UNIX
Version 4.0 operating system
plus any number of additional products installed (such
as System V, DECLadebug, DEC Fortran, and so on). Multiple
environment areas can be established in separate partitions
to support a greater variety
of different environments, improve performance, or support more clients
than allowed by the disk space available in
/var/adm/dms.
The server does not use any of the DMS area. System administrators can access the DMS area as required for maintenance and for installation or removal of layered products, but the area is not used by the server itself.
A DMS
client area
for individual client systems also resides in a DMS area.
Figure 9-3
shows a DMS client area, named
/clients.
The
/clients
area should most likely be located on its own partition after
the size of the area is calculated using the
worksheets in
Appendix B.
Then, the mount point of
/clients
should be added to the
/etc/fstab
file.
Multiple copies of the
root
file system reside in the client area,
one for each client, tailored from the appropriate generic
root
file system.
Each client builds a customized kernel, which resides in
the client's
root
area if the client has a Partial or Full build environment.
This customized kernel supports the
client's actual system configuration, including central processor,
system memory, and peripheral devices.
Figure 9-3
shows two client
root
areas, named
ClientA
and
ClientB.
Each client sees its private
root
area and the shared
/usr
area from the appropriate
/var/adm/dms
environment as local, although these areas are actually on the server
and are accessed through NFS.
Figure 9-4
shows how clients share
/usr
and have their own
root
file system.
Multiple client areas can be established but must reside in different partitions.
Clients do not have access to the entire DMS area. Each DMS
client has access to the
root
area assigned to it on the server.
Common system files residing in the
/usr
area are shared among all the clients registered to that particular
/var/adm/dms
environment. Mounted with
read-only access for the clients, this shared area is protected from
erroneous client activity.
Figure 9-4
illustrates this concept.
In Figure 9-4, the small boxes represent what the clients think they see; the arrows show how the real disk areas on the server are mounted by the client to produce this view.
Clients can be timesharing systems or workstations. Because each
client's
root
area is tailored specifically to the client's needs and would
contain the software the client can run, there is no interference
between clients attempting to use identical resources that could, for
example, have licensing restrictions based on the number of concurrent
users.