mdbm - local name service database
The mdbm client library fetches name service data out of an mdbm(3B)
format database file on the local host. This library is meant to be used
only by the nsd(1M) daemon to efficiently access local name service data.
The library /var/ns/lib/libns_mdbm.so is opened by the nsd(1M) daemon
when mdbm is listed as the protocol for some map in a nsswitch.conf file.
The library contains code to fetch data from a local mdbm file and
present it as lines from the configuration file from which it came. The
nsd daemon then presents that data in the filesystem mounted under /ns.
Extended attributes in the nsswitch.conf file can be used to control the
behavior of the mdbm library. Extended attributes are simply lists of
key/value pairs attached to each object in the nsd filesystem. The
attributes supported in this library are:
This is the domainname given as a parameter to the remote name
server. This attribute is typically inherited from the daemon
depending on the nsswitch.conf file that is being read. Given the
configuration file /var/ns/domains/DOMAINNAME/nsswitch.conf the
attribute "domain" is set to DOMAINNAME. This attribute controls
which file is used to supply the requested information. Given a
domain DOMAINNAME the library would open the file
/var/ns/domains/DOMAINNAME/table.m. If the domain attribute is
unset then the file /etc/table.m would be used. See the information
about the table attribute below. A client system can be a member of
multiple domains by including multiple instances of the mdbm keyword
in the nsswitch.conf file like:
hosts: mdbm(domain=engr) mdbm(domain=corp)
The table attribute is typically inherited from the daemon based on
the line from which this entry occurs in the nsswitch.conf file. In
the above example the table attribute would be set to hosts.byname
or hosts.byaddr depending on the context of the request. This
attribute is used as the file name containing the mdbm data, with a
".m" appended. For the hosts.byname map in the default domain the
file /etc/hosts.byname.m would be opened and searched.
key The key attribute is used to fetch the data from the mdbm(3B) file.
It is set by the nsd(1M) daemon, and is used without alteration.
file The file attribute overrides the domain and table attributes to set
the name of the file to be opened. If the file begins with a
leading '/' then that file is simply opened. If not, then the
contents of this attribute are appended to the directory name --
either /etc/ for the default domain, or /var/ns/domains/DOMAINNAME/
when the domain attribute is set.
The null_extend_key attribute specifies that the null character
which terminates the key is really part of the key. Some
applications (such as sendmail) have historically included the null
in the key so this attribute provides backward compatibility with
the old behavior.
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