NSR(8) Legato NetWorker 4.0 NSR(8)
NAME
NSR - introduction and overview of NetWorker
DESCRIPTION
NetWorker facilitates the backup and recovery of files on a network
of computer systems. Files and file systems may be backed up on a
scheduled basis. Recovery of entire filesystems and single files is
simplified by use of an on-line index of saved files.
NetWorker uses a client-server model to provide the file backup and
recover service. At least one machine on the network is designated
the NetWorker server, and the machines with disks to be backed up are
NetWorker clients. Four daemons provide the NetWorker service, con
trol access to the system, and provide index and media support. On
the clients, there are special programs to access the file systems
and communicate with the NetWorker server.
The NetWorker system has several parts. Commands and files are only
briefly mentioned here, see the appropriate reference manual page for
more detailed information. Each command has a manual page entry in
section 8. The files and their formats are explained in section 5
manual pages.
The NetWorker Administrator's Guide provides information on configur
ing and administering a NetWorker system. It includes many examples
and rationale for setting up and running a successful backup opera
tion.
INSTALLATION
After unloading the NetWorker distribution tape with tar(1) into a
temporary directory, the software must be correctly installed.
nsrize(8) The NetWorker installation script. The script will
install both clients and servers. The nsrize script
is also used to de-install NetWorker.
nsrlayout(5) Describes where NetWorker programs, files and manual
pages are installed.
SERVER DAEMONS
NetWorker uses a client-server model to provide a backup and recover
service. The following daemons encompass the server side of Net
Worker.
nsrd(8) The main NetWorker daemon. nsrd handles initial commu
nication with clients, and starts and stops the other
NetWorker server daemons.
nsrindexd(8) This server daemon provides access to the NetWorker on-
line index. The index holds records of saved files.
The index allows clients to selectively browse and
choose files to recover.
nsrmmdbd(8) The media management database daemon provides an index
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of save sets and media. Nsrmmdbd provides a much
coarser view of the saved files than does nsrindexd, and
therefore the resulting index is usually much smaller.
nsrmmd(8) The media multiplexor daemon provides device support for
NetWorker. When more than one client is saving files,
the data from each client is multiplexed. During recov
ery operations, the data is demultiplexed and sent back
to the requesting client. When the concurrent device
support module is used, several of these daemons may be
active at the same time.
ADMINISTRATION
NetWorker is administered through the attributes of its resources.
These resources may be manipulated by the administrator to change
schedules, start times, group assignments and other aspects of Net
Worker. A detailed resource description is in nsrresource(5).
There is also a manual page for each NetWorker resource in section 5.
networker(8) Monitors the activity of and administers NetWorker
servers. Networker is an X Window System application,
using a look and feel appropriate to the platform on
which it runs. Manual backups and recoveries can also
be initiated through this window tool.
nsradmin(8) A curses(3) based tool for the administration of Net
Worker servers.
nsrwatch(8) A curses(3) based tool to monitor the activity of Net
Worker servers.
nsrmm(8) Media manager command. Nsrmm is used to label, mount,
unmount, delete and purge volumes. Mount requests are
generated by nsrmmd, and displayed by networker or nsr
watch. The size of the on-line user file indexes may be
controlled by deleting and purging volumes.
nsrim(8) Automatically manages the on-line index. Usually run
periodically by savegroup.
mminfo(8) Provides information about volumes and save sets.
nsrck(8) Checks and repairs the NetWorker on-line index. It is
run automatically when nsrd starts up if the databases
were not closed cleanly due to a system crash.
SAVING FILES
NetWorker supports both scheduled and manual saving of files and
filesystems. Each client may be scheduled to save all or part its
filesystem. Different clients may be scheduled to begin saving at
different times.
savegroup(8) Used to initiate the backup of a group of client
machines. Usually started automatically by the server.
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nsrexecd(8) NetWorker-specific remote execution service which runs
on NetWorker clients. Used by savegroup to start savefs
on client machines.
savefs(8) Starts the appropriate save(8) command to back up a
client's filesystem.
saveindex(8) Generates a back up of a client's on-line file index.
When backing up a NetWorker server, a bootstrap save set
is also created.
save(8) Back up a specified file or group of files. Save may be
run manually by users and administrators, or automati
cally by savefs.
RECOVERING FILES
NetWorker maintains an on-line index of user files that have been
saved. Users may browse the index and select files for recovery.
NetWorker then locates the correct volume and recovers the requested
files.
recover(8) Browses the on-line user file index and selects files
and filesystems to recover.
recoverindex(8) Recovers on-line file indexes, including the special
bootstrap index used during disaster recovery.
scanner(8) Verifies correctness of NetWorker volumes. Can also
recover complete save sets and rebuild the on-line
file and media indexes.
nsrcrash(8) A man page describing crash recovery techniques.
APPLICATION SPECIFIC MODULES
In order to process user files in an optimal manner, NetWorker pro
vides the ASM mechanism. Pattern matching is used to select files
for processing by the different ASMs. The patterns and associated
ASMs are described in nsr(5). Save keeps track of which ASMs were
used to process a file so that recover may use the same ASMs to
recover the file.
uasm(8) UNIX filesystem specific save/recover module. The
uasm man page documents the general rules for all
ASMs.
compressasm(8) Compresses files' pages using Lempel-Ziv coding.
mailasm(8) Supports UNIX mailbox conventions.
nsrindexasm(8) Processes the on-line user file indexes.
nsrmmdbasm(8) Processes the media index.
swapasm(8) Handles diskless client swap files.
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xlateasm(8) Implements a simple encryption/decryption scheme on
files.
SERVER LOCATION
On large networks there may be several NetWorker servers installed.
Each NetWorker client command must select a server to use.
For server selection, the client commands are classified into two
groups: administration and operation . The administration commands
include networker, nsrwatch, and mminfo. The operation commands
include save, savefs, and recover. Both groups of commands accept a
-s server option to explicitly specify a server.
When a server is not explicitly specified, the operation commands use
the following steps to locate one. The first server found is used.
1) The machine where the current directory is actually located is
determined. This will either be an NFS server or the local
machine. If that machine is a client of a NetWorker server as
determined by a RAP query, then that NetWorker server is used.
2) The machine where the current directory is actually located is
examined to see if it is a NetWorker server. If it is, then it
is used.
3) The local machine is examined to see if it is a NetWorker
server. If it is, then it is used.
4) If a NetWorker server has still not been found, then the machine
with the hostname ``nsrhost'' is used.
The administrative commands start with step number 3, and follow it
with steps 1, 2 and finally 4. When either set of commands fail to
find a NetWorker server, an error message is printed. The nsradmin
command (when not given a -s server option), can be used with all
servers in the RAP area if a rapd daemon is running on the local
machine, or the host named ``nsrhost''. Otherwise, the local machine
is used if it is a server, or the host named ``nsrhost''. The nsrmm
command always uses the local server, unless given the -s server
option. Some commands now use a broadcast to locate servers.
When there is only one NetWorker server on the network, or to desig
nate a ``primary'' server, add a ``nsrhost'' alias for the appropri
ate machine to your host table. For example, edit the file
``/etc/hosts'' if you are using a file for your host table. When
running the Network Information System (NIS, formerly called Yellow
Pages or YP), add the ``nsrhost'' alias on the master and push the
``hosts'' map. Otherwise, add the ``nsrhost'' alias to the
/etc/hosts file for every client and the server. See ypfiles(5) and
ypmake(8).
SECURITY
Before a save is allowed, there must be an NSR client resource cre
ated for the given client. Before a recovery is allowed, the server
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validates client access by checking the recover access attribute in
the NSR client resource (see nsrclient(5)). The server will only
accept connections that are initiated from a reserved port. Reserved
ports can only be opened by root, so most NetWorker programs run by
the super-user, or set-uid to root. This access control is similar
to that used by the rsh(1) command except that instead of using the
/.rhosts file, NetWorker uses the recover access list in the NSR
client resource.
Once a connection has been established, the client programs: save(8),
savefs(8), and recover(8), set their effective uid to the uid of the
user who initiated the program so that all local filesystem and sys
tem call access is done as that user. This prevents users from recov
ering files to which they should not have access. The exception to
this rule is that the user name ``operator'' and users in the group
``operator'' receive filesystem access privileges of the super-user.
This allows the administrator to set up a user name or group for the
operators who will initiate saves and recovers on behalf of other
users, without giving the operators root access to client machines.
Access control for the client programs can be further tightened by
turning off the set-uid bit. This will restrict the use of these pro
grams to root only on the client machines. To allow access by root
and operator, but not by other users, change the group ownership of
these programs to ``operator'', and set the mode bits to allow execu
tion by owner and group, but not by others.
The savegroup(8) command initiates the savefs(8) command on each
client machine in an NSR group by using the nsrexecd(8) remote save
execution service. See the nsrexecd(8) man page for details. For
backward compatibility with older versions of NetWorker, savegroup(8)
will fall back on using the rsh(1) protocol for remote execution if
nsrexecd is not running on a particular client.
Access to the NSR resources through the nsradmin(8) or networker(8)
commands is controlled by the administrator attribute on each
resource. This attribute has a list of names of the users who have
permission to administer that resource. Names that begin with an
ampersand (&) denote netgroups (see netgroup(5)). Also names can be
of the form user@host to authorize a specific user on a specific
host.
NAMING AND AUTHENTICATION
As described above, the NSR server only accepts connections initiated
from a secure port on the machines listed as clients or listed in the
recover access list (for recovering). Since machines may be con
nected to more than one physical network and since each physical net
work connection may have numerous aliases, the policies below are
used as a compromise between security and ease of use. For further
information about naming in the UNIX environment, refer to gethos
tent(3), or other documentation on name services.
A client determines its own name as follows. First the client's UNIX
system name is acquired via the gethostname(2) system call. The UNIX
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system name is used as a parameter to the gethostbyname(3) library
routine. The client declares its name to be the official (or ``pri
mary'') name returned by gethostbyname. This name is passed to the
NetWorker server during connection establishment.
A server authenticates a client connection by reconciling the connec
tion's remote address with client's stated name. The address is
mapped to a list of host names via the gethostbyaddr(3) library func
tion. Next, the client's stated name is used as a parameter to geth
ostbyname to acquire another list of host names. The client is suc
cessfully authenticated if and only if there exists a common name
between the two lists.
The NetWorker server maps a client's name to an on-line index
database name by resolving the client's name to the official name
returned by gethostbyname. This mapping takes place both at client
creation time and at connection establishment time.
To ensure safe and effective naming, the following rules should be
employed:
1) The NetWorker clients and servers should access consistent host
name databases. NIS (YP) and the Domain Name System (DNS) are
naming subsystems that aid in host name consistency.
2) All hosts entries for a single machine should have at least one
common alias among them.
3) When creating a new client, use a name or alias that will map
back to the same official name that the client machine produces
by backward mapping its UNIX system name.
SEE ALSO
rsh(1), nsr(5), nsrlayout(5), mminfo(8), networker(8), nsrcrash(8),
nsrize(8), nsrresource(5), nsradmin(8), nsrck(8), nsrd(8),
nsrexecd(8), nsrim(8), nsrindexd(8), nsrls(8), nsrmm(8), nsrmmd(8),
nsrmmdbd(8), nsrwatch(8), rap(8), rapd(8), recover(8),
recoverindex(8), save(8), savefs(8), uasm(8), savegroup(8),
saveindex(8), scanner(8), netgroup(5), ypfiles(5), ypmake(5),
gethostname(2), gethostent(3).
The NetWorker Administrator's Guide
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