ypfiles.5yp

<B>Digital的Unix操作系统VAX 4.2源码</B>

.\" SCCSID: @(#)ypfiles.5yp	8.2	11/9/90
.TH ypfiles 5yp
.SH Name
ypfiles \- Yellow Pages data base and directory structure
.SH Description
.NXR "ypfiles keyword"
.NXR "YP map" "format"
.NXR "YP map" "defined"
.NXR "YP domain" "defined"
The Yellow Pages (YP) data base lookup service uses a data base of
.PN dbm
files in the 
.PN /etc/yp
directory hierarchy.
A
.PN dbm
data base consists of two files, created by calls to the 
.MS dbm 3x
library package.  One has the filename extension 
.PN \&.pag
and the other has the filename extension 
.PN \&.dir .
For instance, the data base named
.PN hosts.byname ,
is implemented by the pair of files 
.PN hosts.byname.pag
and
.PN hosts.byname.dir .
.PP
A
.PN dbm
data base served by YP is called a YP 
.I map.
A YP
.I domain
is a named set of YP maps.  
Each YP domain is implemented as a subdirectory of 
.PN /etc/yp 
containing the maps.
The number of YP domains that can exist is unlimited.
Each domain can contain any number of 
maps.
.PP
The YP maps are not required by the YP lookup service, although they may
be required for the normal operation of other parts of the system.
The YP lookup service serves all maps. If the map exists in a given
domain and a client asks about it, YP will serve it.  There is,
however, a set of default maps that the YP service serves.  The files
representing these maps are listed in this description under Files.
.PP
For a map to be accessible consistently, it must exist on all YP
servers that serve the domain.  To provide data consistency between the
replicated maps, an entry to execute the 
.PN ypxfr
command periodically should be made in the 
.PN /usr/lib/crontab
file on each slave server.  More information on this topic is in 
.MS ypxfr 8yp .
An entry in the 
.PN /etc/lib/crontab
file must not exist, either on a YP master server or on a pure YP client
machine.
.PP
The YP maps should contain two distinguished
key-value pairs.  The first is
the key YP_LAST_MODIFIED, whose value is a 10-character 
ASCII order number.  The order number should be the \s-2UNIX\s0 time 
in seconds when the map was built.  The second key is YP_MASTER_NAME, 
with the name of the YP master server as a value.  
The 
.MS makedbm 8yp
command generates both key-value pairs automatically.
A map that does not contain both key-value pairs can be served by 
the YP, but the 
.PN ypserv 
process will not be able to return values for ``Get order number''
or ``Get master name'' requests.  
In addition, values of these two keys are used by
.MS ypxfr 8yp
when it transfers a map from a master YP server to a slave.
.PP
Before they can be properly accessed, the YP maps must be initially
set up for both masters and slaves by using the
.MS ypsetup 8yp
function.
Further, YP maps must be generated and modified only
at the master server
location.  Copies of the master server YP maps can then
be transferred to the
slave servers using the 
.MS ypxfr 8yp
function.
If 
.PN ypxfr 
is unable to determine a map's location, or if it is unable to
determine whether the local copy is more 
recent than the master copy, extra command line 
switches must be set when it is executed.
.PP
After the server data bases are set up, the contents of
some maps may change.  In general, some ASCII source version of the
data base exists on the master. 
This version should be changed with a standard text
editor.  The update is incorporated into the YP
map and is propagated from
the master to the slaves by running 
.PN /etc/yp/Makefile .
All maps must have entries in 
.PN /etc/yp/Makefile .
If a YP map is added, the 
.PN /etc/yp/Makefile
must be edited to support the new map.
The makefile uses 
.MS makedbm 8yp
to generate the YP map on the master, and
.MS yppush 8yp
to propagate the changed map to the slaves.  
The 
.MS yppush 8yp
command is a client of the map
.I ypservers,
which lists all of the YP servers.  
.SH Files
.PN /etc/passwd
.br
.PN /etc/group
.br
.PN /etc/hosts
.br
.PN /etc/networks
.br
.PN /etc/services
.br
.PN /etc/protocols
.br
.PN /etc/netgroup
.SH See Also
makedbm(8yp), rpcinfo(8nfs), ypmake(8yp), yppoll(8yp),
yppush(8yp), ypserv(8yp), ypsetup(8yp), ypxfr(8yp)