NISLDAPMAPPING(5) Standards, Environments, and Macros NISLDAPMAPPING(5)


NISLDAPmapping - mapping file used by the NIS server components




The NISLDAPmapping file specifies the mapping between NIS map entries and
equivalent Directory Information Tree (DIT) entries.

The presence of /var/yp/NISLDAPmapping on a NIS master server causes that
server to obtain NIS data from LDAP. See ypserv(5). If
/var/yp/NISLDAPmapping is present but the connection configuration file
that is defined in /etc/default/ypserv cannot be found, a warning is
logged. See ypserv(8).

NIS slave servers always obtain their data from a NIS master server,
whether or not that server is getting data from LDAP, and ignore the
/var/yp/NISLDAPmapping file.

A simple NISLDAPmapping file is created using inityp2l(8). You can
customize your NISLDAPmapping file as you require.

Each attribute defined below can be specified in /var/yp/NISLDAPmapping
or as an LDAP attribute. If both are specified, then the attribute in
/var/yp/NISLDAPmapping (including empty values) takes precedence.

A continuation is indicated by a '\' (backslash) in the last position,
immediately before the newline of a line. Characters are escaped, that
is, exempted from special interpretation, when preceded by a backslash

The '#' (hash) character starts a comment. White space is either ASCII
space or a horizontal tab. In general, lines consist of optional white
space, an attribute name, at least one white space character, and an
attribute value.


File Syntax

Repeated fields, with separator characters, are described by the
following syntax:

One or more entries


Zero or more entries



Attributes generally apply to one more more NIS maps. Map names can be
specified either on their own, that is in passwd.byname, in which case
they apply to all domains, or for individual NIS domains, for example, in
passwd.byname, Where a map is mentioned in more than one
attribute, both versions are applied. If any parts of the attributes are
in conflict, the domain specific version takes precedence over the non-
domain specific version.

Each domain specific attributes must appear in NISLDAPmapping before any
related non-domain specific attribute. If non-domain specific attributes
appear first, behavior may be unpredictable. Errors are logged when non-
domain specific attributes are found first.

You can associate a group of map names with a databaseId. In effect, a
macro is expanded to the group of names. Use this mechanism where the
same group of names is used in many attributes or where domain specific
map names are used. Then, you can make any changes to the domain name in
one place.

Unless otherwise noted, all elements of the syntaxes below may be
surrounded by white space. Separator characters and white space must be
escaped if they are part of syntactic elements.

The following attributes are recognized.


The context to use for a NIS domain.

The syntax for nisLDAPdomainContext is:

NISDomainName ":" context

The following is an example of the nisLDAPdomainContext attribute: : dc=site, dc=example, dc=com

The mapping file should define the context for each domain before any
other attribute makes use of the NISDomainName specified for that


Lists the domains for which password changes should be made. NIS
password change requests do not specify the domains in which any
given password should be changed. In traditional NIS this information
is effectively hard coded in the NIS makefile.

The syntax for the nisLDAPyppasswddDomains attribute is:


If there are multiple domains, use multiple nisLDAPyppasswddDomain
entries with one domainname per entry.


Sets up an alias for a group of NIS map names. There is no default

The syntax for the nisLDAPdatabaseIdMapping attribute is:

databaseId ":" ["["indexlist"]"] mapname[" "...]


databaseId = Label identifying a (subset of a) NIS
object for mapping purposes.
indexlist = fieldspec[","...]
fieldspec = fieldname "=" fieldvalue
fieldname = The name of a entry field as defined in
fieldvalue = fieldvaluestring | \" fieldvaluestring \"

indexlist is used for those cases where it is necessary to select a
subset of entries from a NIS map. The subset are those NIS entries
that match the indexlist. If there are multiple specifications
indexed for a particular NIS map, they are tried in the order
retrieved until one matches. Note that retrieval order usually is
unspecified for multi-valued LDAP attributes. Hence, if using indexed
specifications when nisLDAPdatabaseIdMapping is retrieved from LDAP,
make sure that the subset match is unambiguous.

If the fieldvaluestring contains white space or commas, it must
either be surrounded by double quotes, or the special characters must
be escaped. Wildcards are allowed in the fieldvaluestring. See

To associate the passwd.byname and passwd.byuid maps with the passwd

passwd:passwd.byname passwd.byuid

The passwd and passwd.adjunct databaseIds receive special handling.
In addition to its normal usage, passwd defines which maps yppasswdd
is to update when a passwd is changed. In addition to its normal
usage passwd.adjunct defines which maps yppasswdd is to update when
an adjunct passwd is changed.

You may not alias a single map name to a different name, as the
results are unpredictable.


Establish TTLs for NIS entries derived from LDAP.

The syntax for the nisLDAPentryTtl attribute is:

mapName[" "...]":"
initialTTLlo ":" initialTTLhi ":" runningTTL


The lower limit for the initial TTL (in seconds) for
data read from LDAP when the ypserv starts. If the
initialTTLhi also is specified, the actual initialTTL
will be randomly selected from the interval
initialTTLlo to initialTTLhi, inclusive. Leaving the
field empty yields the default value of 1800 seconds.

The upper limit for the initial TTL. If left empty,
defaults to 5400 seconds.

The TTL (in seconds) for data retrieved from LDAP
while the ypserv is running. Leave the field empty
to obtain the default value of 3600 seconds.

If there is no specification of TTLs for a particular map, the
default values are used.

If the initialTTLlo and initialTTLhi have the same value, the effect
will be that all data known to the ypserv at startup times out at the
same time. Depending on NIS data lookup patterns, this could cause
spikes in ypserv-to-LDAP traffic. In order to avoid that, you can
specify different initialTTLlo and initialTTLhi values, and obtain a
spread in initial TTLs.

The following is an example of the nisLDAPentryTtl attribute used to
specify that entries in the NIS host maps read from LDAP should be
valid for four hours. When ypserv restarts, the disk database entries
are valid for between two and three hours.

hosts.byname hosts.byaddr:7200:10800:14400


Specifies the connection between a group of NIS maps and the LDAP
directory. This attribute also defines the 'order' of the NIS maps.
When NIS maps are bulk copied to or from the DIT, they are processed
in the same order as related nisLDAPobjectDN attributes appear in

The syntax for the nisLDAPobjectDN attribute is:

mapName[" "...] ":" objectDN *( ";" objectDN )


objectDN = readObjectSpec [":"[writeObjectSpec]]
readObjectSpec = [baseAndScope [filterAttrValList]]
writeObjectSpec = [baseAndScope [attrValList]]
baseAndScope = [baseDN] ["?" [scope]]
filterAttrValList = ["?" [filter | attrValList]]]
scope = "base" | "one" | "sub"
attrValList = attribute "=" value
*("," attribute "=" value)

The baseDN defaults to the value of the nisLDAPdomainContext
attribute for the accessed domain. If the baseDN ends in a comma, the
nisLDAPdomainContext value is appended.

scope defaults to one. scope has no meaning and is ignored in a

The filter is an LDAP search filter and has no default value.

The attrValList is a list of attribute and value pairs. There is no
default value.

As a convenience, if an attrValList is specified in a readObjectSpec,
it is converted to a search filter by ANDing together the attributes
and the values. For example, the attribute and value list:


is converted to the filter:


Map entries are mapped by means of the relevant mapping rules in the
nisLDAPnameFields and nisLDAPattributeFromField .

If a writeObjectSpec is omitted, the effect is one of the following:

o If there is no trailing colon after the readObjectSpec,
then there is no write at all.

o If there is a colon after the readObjectSpec, then
writeObjectSpec equals readObjectSpec.
The following is an example of a nisLDAPobjectDN attribute
declaration that gets the hosts.byaddr map entries from the ou=Hosts
container under the default search base and writes to the same place.


The following is an example of a nisLDAPobjectDN attribute
declaration that obtains passwd map entries from the ou=People
containers under the default search base, and also from



Specifies the content of entries in a NIS map and how they should be
broken into named fields. nisLDAPnameFields is required because NIS
maps do not store information in named fields.

The syntax for the nisLDAPnameFields attribute is as follows:

"nisLDAPnameFields" mapName ":" "(" matchspec "," fieldNames ")"
fieldName = nameOrArrayName[","...]
nameOrArrayName = Name of field or 'array' of repeated fields.
matchspec = \" formatString \"

formatString may contain a list of %s and %a elements each of which
represents a single named field or a list of repeated fields. A %a
field is interpreted as an IPv4 address or an IPv6 address in
preferred format. If an IPv6 address in non preferred format is
found, then it is converted and a warning is logged.

Where there are a list of repeated fields, the entire list is stored
as one entry. The fields are broken up into individual entries, based
on the internal separator, at a latter stage. Other characters
represent separators which must be present. Any separator, including
whitespace, specified by the formatString, may be surrounded by a
number of whitespace and tab characters. The whitespace and tab
characters are ignored.

Regardless of the content of this entry some fieldNames are reserved:

The DBM key value.

The DBM key value handled as an IP address. See the
discussion of %a fields.

Everything following the first occurrence of a
symbol. rf_comment is defined by

The name of the domain in which the current NIS
operation is being carried out.

The rf_searchkey value handled as an IP address.
See the discussion of %a fields above.

See the description under nisLDAPattributeFromField

For example, the rpc.bynumber map has the format:

name number alias[" "...]

The NIS to LDAP system is instructed to break it into a name, a
number, and an array of alias field by the following entry in the
mapping file:

nisLDAPnameFields rpc.bynumber : \
"%s %s %s", name,number,aliases)


Defines how a field, or list of fields, named by nisLDAPnameFields is
split into subfields. The original field is compared with each line
of this attribute until one matches. When a match is found named
subfields are generated. In latter operations subfield names can be
used in the same way as other field names.

The syntax for the nisLDAPsplitFields attribute is as follows:

"nisLDAPsplitFields" fieldName ":" splitSpec[","...]
splitSpec = "(" matchspec "," subFieldNames ")"
fieldName = Name of a field from nisLDAPnameFields
subFieldNames = subFieldname[","...]
matchspec = \" formatString \"

The netgroup memberTriples can have format (host, user, domain) or
groupname. The format is specified by the attribute:

nisLDAPsplitField memberTriple: \
("(%s,%s,%s)", host, user, domain) , \
("%s", group)

Later operations can then use field names host, user, domain, group
or memberTriple. Because lines are processed in order, if host, user
and domain are found, group will not be generated.

Several maps and databaseIds may contain fields that are to be split
in the same way. As a consequence, the names of fields to be split
must be unique across all maps and databaseIds.

Only one level of splitting is supported. That is, a subfield cannot
be split into further subfields.


Where there is a list of repeated, splittable fields,
nisLDAPrepeatedFieldSeparators specifies which characters separate
instances of the splittable field.

The syntax for the nisLDAPrepeatedFieldSeparators attribute is as

"nisLDAPrepeatedFieldSeparators" fieldName \"sepChar[...]\"
sepChar = A separator character.

The default value is space or tab. If repeated splittable fields are
adjacent, that is, there is no separating character, then the
following should be specified:

nisLDAPrepeatedFieldSeparators netIdEntry: ""


Specifies which character represents the start of the special comment
field in a given NIS map. If this attribute is not present then the
default comment character # is used.

To specify that a map uses an asterisk to mark the start of comments.

nisLDAPcommentChar mapname : '*'

If a map cannot contain comments, then the following attribute should
be specified.

nisLDAPcommentChar mapname : ''


Indicates if YP_INTERDOMAIN or YP_SECURE entries should be created
in a map. Using nisLDAPmapFlags is equivalent to running makedbm(8)
with the -b or the -s option. When a map is created from the contents
of the DIT, the mapping file attribute is the only source for the

The syntax for the nisLDAPmapFlags attribute is as follows:

"nisLDAPmapFlags" mapname ":" ["b"]["s"]

By default neither entry is created.


Specifies how a NIS entries field values are derived from LDAP
attribute values.

The syntax for the nisLDAPfieldFromAttribute attribute is as follows:

mapName ":" fieldattrspec *("," fieldattrspec)

The format of fieldattrspec is shown below at Field and Attribute
Conversion Syntax.

To map by direct copy and assignment the value of the ipHostNumber
attribute to the addr named field, for example:


Formats for the named field and attribute conversion syntax are
discussed below, including examples of complex attribute to field


Specifies how an LDAP attribute value is derived from a NIS entry
field value.

The syntax for the nisLDAPattributeFromField attribute is as follows:

mapName ":" fieldattrspec *("," fieldattrspec )

The format of fieldattrspec is shown below at Field and Attribute
Conversion Syntax.

As a special case, if the dn attribute value derived from a
fieldattrspec ends in a comma (","), the domains context from
nisLDAPdomainContext is appended.

Use the following example to map the value of the addr field to the
ipHostNumber attribute by direct copy and assignment:


All relevant attributes, including the dn, must be specified.

For every map it must be possible to rapidly find a DIT entry based
on its key. There are some maps for which a NIS to LDAP mapping for
the key is not desirable, so a key mapping cannot be specified. In
these cases a mapping that uses the reserved rf_searchkey must be
specified. Mappings that use this field name are ignored when
information is mapped into the DIT.

Field and Attribute Conversion Syntax

The general format of a fieldattrspec is:

fieldattrspec = lhs "=" rhs
lhs = lval | namespeclist
rhs = rval | [namespec]
namespeclist = namespec | "(" namespec *("," namespec) ")"

The lval and rval syntax are defined below at Values. The format of a
namespec is:


["ldap:"] attrspec [searchTriple] | ["yp:"] fieldname


field | "(" field ")"


attribute | "(" attribute ")"


":" [baseDN] ["?" [scope] ["?" [filter]]]

Base DN for search

LDAP search filter

Map name

The repository specification in a namespec defaults is as follows:

o For assignments to a field:

on the LHS

on the RHS

NIS field values on the RHS are those that exist before the NIS entry
is modified.

o For assignments to an attribute:

on the LHS

on the RHS

Attribute values on the RHS are those that exist before the LDAP
entry is modified.

When the field or attribute name is enclosed in parenthesis, it denotes a
list of field or attribute values. For attributes, the meaning is the
list of all attributes of that name, and the interpretation depends on
the context. See the discussion at Values. The list specification is
ignored when a searchTriple or mapspec is supplied.

For fields, the fieldname syntax is used to map multiple attribute
instances to multiple NIS entries.

The searchTriple can be used to specify an attribute from a location
other than the read or write target. The defaultvalues are as follows:

If baseDN is omitted, the default is the current objectDN. If
the baseDN ends in a comma, the context of the domain is
appended from nisLDAPdomainContext .



Similarly, the mapspec can be used to specify a field value from a NIS
map other than the one implicitly indicated by the mapName. If
searchTriple or mapspec is explicitly specified in a namespec, the
retrieval or assignment, whether from or to LDAP or NIS, is performed
without checking if read and write are enabled for the LDAP container or
NIS map.

The omission of the namespec in an rhs is only allowed if the lhs is one
or more attributes. The effect is to delete the specified attribute(s).
In all other situations, an omitted namespec means that the rule is

The filter can be a value. See Values. For example, to find the
ipHostNumberthat uses the cn, you specify the following in the filter

ldap:ipHostNumber:?one?("cn=%s", (cname, "%s.*"))

In order to remove ambiguity, the unmodified value of a single field or
attribute must be specified as the following when used in the filter

("%s", namespec)

If the filter is not specified, the scope will be base, and the baseDN is
assumed to be the DN of the entry that contains the attribute to be
retrieved or modified. To use previously existing field or attribute
values in the mapping rules requires a lookup to find those values.
Obviously, this adds to the time required to perform the modification.
Also, there is a window between the time when a value is retrieved and
then slightly later stored back. If the values have changed in the
meantime, the change may be overwritten.

When fieldattrspecs are grouped into rule sets, in the value of a
nisLDAPfieldFromAttribute or nisLDAPattributeFromField attribute, the
evaluation of the fieldattrspecs proceed in the listed order. However,
evaluation may be done in parallel for multiple fieldattrspecs. If there
is an error when evaluating a certain fieldattrspec, including retrieval
or assignment of entry or field values, the extent to which the other
fieldattrspec rules are evaluated is unspecified.


Where wildcard support is available, it is of the following limited form:

Matches any number of characters

Matches the character x

Matches any character in the range x to y, inclusive

Combinations such as [a-cA-C0123] are also allowed, which would match any
one of a, b, c, A, B, C, 0, 1, 2, or 3.

Substring Extraction

substringextract = "(" namespec "," matchspec ")"
name = field or attribute name
matchspec =

The matchspec is a string like the sscanf(3C) format string, except that
there may be at most one format specifier, a single %s. The output value
of the substringextract is the substring that matches the location of the

If there is no %s in the formatstring, it must instead be a single
character, which is assumed to be a field separator for the namespec. The
output values are the field values. Wild cards are supported. If there is
no match, the output value is the empty string, " ".

For example, if the fieldcname has the value, the
value of the expression:

(cname, "%s.*")

is user, which can be used to extract the user name from a NIS principal

Similarly, use this expression to extract the third of the colon-
separated fields of the shadow field:

(shadow, "*:*:%s:*")

This form can be used to extract all of the shadow fields. However, a
simpler way to specify that special case is:

(shadow, ":")


lval = "(" formatspec "," namespec *("," namespec) ")"
rval = "(" formatspec ["," namelist ["," elide] ] ")"

namelist = name_or_sse *( "," name_or_sse)
name_or_sse = namespec | removespec | substringextract
removespec = list_or_name "-" namespec
list_or_name = "(" namespec ")" | namespec
formatspec =
formatstring = A string combining text and % field specifications
elide =
singlechar = Any character

The syntax above is used to produce rval values that incorporate field or
attribute values, in a manner like sprintf(3C), or to perform assignments
to lval like sscanf(3C). One important restriction is that the format
specifications,% plus a single character, use the designations from
ber_printf(3LDAP). Thus, while %s is used to extract a string value, %i
causes BER conversion from an integer. Formats other than %s, for
instance, %i, are only meaningfully defined in simple format strings
without any other text.

The following ber_printf() format characters are recognized:

b i n o s

If there are too few format specifiers, the format string may be repeated
as needed.

When used as an lval, there is a combination of pattern matching and
assignment, possibly to multiple fields or attributes.

In an assignment to an attribute, if the value of the addr field is, the rval:

("ipNetworkNumber=%s,", addr)

produces the value ipNetworkNumber=,, while:

("(%s,%s,%s)", host, user, domain)

results in:

(assuming host="xyzzy", user="-", domain="x.y.z")

The elide character feature is used with attribute lists. So:

("%s,", (mgrprfc822mailmember), ",")

concatenates all mgrprfc822mailmember values into one comma-separated
string, and then elides the final trailing comma. Thus, for


the value would be:


As a special case, to combine an LHS extraction with an RHS implicit list
creates multiple entries and values. So

("(%s,%s,%s)", host, user, domain)=(nisNetgroupTriple)

creates one NIS entry for each nisNetgroupTriple value.

The 'removespec' form is used to exclude previously assigned fields
values from a list. So, if an LDAP entry contains:

name: foo
cn: foo
cn: foo1
cn: foo2

and the mapping file specifies :

myName = name, \
myAliases = ("%s ", (cn) - yp:myName, " ")

then the following assignments are carried out:

1. Assign value foo to myName

2. Assign value foo foo1 foo2 to myAliases

3. Remove value of myName from value myAliases

This results in the field values myName is set to foo, and myAliases is
set to foo1 foo2.


The assignment syntax, also found at Field and Attribute Conversion
Syntax, is as follows:

fieldattrspec = lhs "=" rhs
lhs = lval | namespeclist
rhs = rval | namespec
namespeclist = namespec | "(" namespec *("," namespec) ")"

The general form of a simple assignment, which is a one-to-one mapping of
field to attribute, is:

("%s", fieldname)=("%s", attrname)

As a convenient shorthand, this can also be written as:


A list specification, which is a name enclosed in parenthesis, can be
used to make many-to-many assignments. The expression:


where there are multiple instances of attrname, creates one NIS entry for
each such instance, differentiated by their fieldname values. The
following combinations of lists are allowed, but they are not
particularly useful:

Equivalent to attrname=fieldname

Equivalent to attrname=fieldname

Equivalent to fieldname=attrname

Equivalent to fieldname=attrname

If a multi-valued RHS is assigned to a single-valued LHS, the LHS value
will be the first of the RHS values. If the RHS is an attribute list, the
first attribute is the first one returned by the LDAP server when
queried. Otherwise, the definition of "first" is implementation

Finally, the LHS can be an explicit list of fields or attributes, such


If the RHS is single-valued, this assigns the RHS value to all entities
in the list. If the RHS is multi-valued, the first value is assigned to
the first entity of the list, the second value to the second entity, and
so on. Excess values or entities are silently ignored.


Example 1: Assigning an Attribute Value to a Field

The following example illustrates how to assign the value of the
ipHostNumber attribute to the addr field


Example 2: Creating Multiple NIS Entries from Multi-Valued LDAP Attributes

An LDAP entry with:


and the following assignments:


creates three NIS entries. Other attributes and fields are omitted for

cname=name1, name=name1
cname=name1, name=name2
cname=name1, name=name3

Example 3: Assigning String Constants

The following expression sets the passwd field to x:


Example 4: Splitting Field Values to Multi-Valued Attributes

The expansion field contains a comma-separated list of alias member
names. In the following example, the expression assigns each member name
to an instance of mgrprfc822mailmember:

(mgrprfc822mailmember)=(expansion, ",")


Mapping file used by the NIS server components


See attributes(7) for descriptions of the following attributes:

|Interface Stability | Obsolete |


sprintf(3C), sscanf(3C), ber_printf(3LDAP), ypserv(5), attributes(7),
inityp2l(8), makedbm(8), ypserv(8)

System Administration Guide: Naming and Directory Services (DNS, NIS, and

November 22, 2021 NISLDAPMAPPING(5)