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The rpc.yppasswdd utility allows a normal NIS user to change his or her NIS password, full name (also known as 'GECOS' field) or shell. These updates are typically done using the yppasswd(1), ypchfn(1), ypchsh(1), or ypchpass(1) commands. (Some administrators do not want users to be able to change their full name information or shells; the server can be invoked with option flags that disallow such changes.) When the server receives an update request, it compares the address of the client making the request against the securenets rules outlined in /var/yp/securenets. (See the ypserv(8) manual page for more information on securenets; the rpc.yppasswdd utility uses the same access control mechanism as ypserv(8).)
The server then checks the 'old' password supplied by the user to make sure it is valid, then performs some sanity checks on the updated information (these include checking for embedded control characters, colons or invalid shells). Once it is satisfied that the update request is valid, the server modifies the template password file (the default is /var/yp/master.passwd) and then runs the /usr/libexec/yppwupdate script to rebuild the NIS maps. (This script has two arguments passed to it: the absolute pathname of the password template that was modified and the name of the domain that is to be updated. These in turn are passed to /var/yp/Makefile).
also allows the super-user on the NIS master server to perform more
sophisticated updates on the NIS passwd maps.
The super-user can modify
any field in any user's master.passwd entry in any domain, and can
do so without knowing the user's existing NIS password (when the server
receives a request from the super-user, the password authentication
check is bypassed).
Furthermore, if the server is invoked with the
The rpc.yppasswdd utility can only be run on a machine that is an NIS master server.
assumes that the template file used to generates the
maps for the default domain is called
This default can be overridden by specifying an alternate file name
Note: if the template file specified with this flag is /etc/master.passwd, rpc.yppasswdd will also automatically invoke pwd_mkdb(8) to rebuild the local password databases in addition to the NIS maps.
|The rpc.yppasswdd utility can support multiple domains, however it must choose one domain as a default. It will try to use the system default domain name as set by the domainname(1) command for this default. However, if the system domain name is not set, a default domain must be specified on the command line. If the system default domain is set, then this option can be used to override it.|
|This option can be used to override the default path to the location of the NIS map databases. The compiled-in default path is /var/yp.|
|Disallow changing of shell information.|
|Disallow changing of full name ('GECOS') information.|
|Allow additions to be made to the NIS passwd databases. The super-user on the NIS master server is permitted to use the ypchpass(1) command to perform unrestricted modifications to any field in a user's master.passwd map entry. When rpc.yppasswdd is started with this flag, it will also allow the super-user to add new records to the NIS passwd maps, just as is possible when using chpass(1) to modify the local password database.|
Turn on multi-domain mode.
can handle several simultaneous domains, most implementations of
can only operate on a single NIS domain, which is generally the same as
the system default domain of the NIS master server.
attempts to overcome this problem in spite of the inherent limitations
protocol, which does not allow for a
argument in client requests.
In multi-domain mode,
will search through all the passwd maps of all the domains it
can find under
until it finds an entry that matches the user information specified in
a given update request.
(Matches are determined by checking the username,
UID and GID fields.)
The matched entry and corresponding domain are then
used for the update.
Note that in order for multi-domain mode to work, there have to be separate template files for each domain. For example, if a server supports three domains, foo, bar, and baz, there should be three separate master.passwd template files called /var/yp/foo/master.passwd, /var/yp/bar/master.passwd, and /var/yp/baz/master.passwd. If foo happens to be the system default domain, then its template file can be either /var/yp/foo/master.passwd or /var/yp/master.passwd. The server will check for the latter file first and then use the former if it cannot find it.
Multi-domain mode is off by default since it can fail if there are duplicate or near-duplicate user entries in different domains. The server will abort an update request if it finds more than one user entry that matches its search criteria. Even so, paranoid administrators may wish to leave multi-domain mode disabled.
|If rpc.yppasswdd is invoked with this flag, it will perform map updates in place. This means that instead of just modifying the password template file and starting a map update, the server will modify the map databases directly. This is useful when the password maps are large: if, for example, the password database has tens of thousands of entries, it can take several minutes for a map update to complete. Updating the maps in place reduces this time to a few seconds.|
Turn on verbose logging mode.
The server normally only logs messages
facility when it encounters an error condition, or when processing
updates for the super-user on the NIS master server.
Running the server
clients do not use a reserved port when sending requests to
This is either because the
program is not installed set-uid root, or because the RPC
implementation does not place any emphasis on binding to reserved
ports when establishing client connections for the super-user.
expects to receive requests from clients using reserved ports; requests
received from non-privileged ports are rejected.
behavior prevents any client systems that to not use privileged
ports from successfully submitting password updates.
|Display the list of flags and options understood by rpc.yppasswdd.|
|The script invoked by rpc.yppasswdd to update and push the NIS maps after an update.|
|The template password file for the default domain.|
|The NIS maps for a particular NIS domain.|
|The template password file(s) for non-default domains (used only in multi-domain mode).|
This is not a problem for password updates since the plaintext password sent with the update will no longer be valid once the new encrypted password is put into place, but if the user is only updating his or her 'GECOS' information or shell, then the cleartext password sent with the update will still be valid once the update is completed. If the network is insecure, this cleartext password could be intercepted and used to gain unauthorized access to the user's account.
|RPC.YPPASSWDD (8)||February 8, 1996|
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|“||"I liken starting one's computing career with Unix, say as an undergraduate, to being born in East Africa. It is intolerably hot, your body is covered with lice and flies, you are malnourished and you suffer from numerous curable diseases. But, as far as young East Africans can tell, this is simply the natural condition and they live within it. By the time they find out differently, it is too late. They already think that the writing of shell scripts is a natural act."||”|
|— Ken Pier, Xerox PARC|