openldap/doc/guide/admin/dbtools.sdf

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H1: Database Creation and Maintenance Tools

This section tells you how to create a slapd database from
scratch, and how to do trouble shooting if you run into
problems. There are two ways to create a database. First,
you can create the database on-line using LDAP. With this
method, you simply start up slapd and add entries using the
LDAP client of your choice. This method is fine for relatively
small databases (a few hundred or thousand entries,
depending on your requirements).

The second method of database creation is to do it off-line,
using the index generation tools. This method is best if you
have many thousands of entries to create, which would take
an unacceptably long time using the LDAP method, or if you
want to ensure the database is not accessed while it is
being created.


H2: Creating a database over LDAP

With this method, you use the LDAP client of your choice
(e.g., the ldapadd(1) tool) to add entries, just like you would
once the database is created. You should be sure to set the
following configuration options before starting slapd:

E:	suffix <dn>

As described in the preceding section, this option says what
entries are to be held by this database. You should set this
to the DN of the root of the subtree you are trying to create.
For example

E: 	suffix "dc=OpenLDAP, dc=org"

You should be sure to specify a directory where the index
files should be created:

E:	directory <directory>

For example:

E:	directory /usr/local/openldap/slapd

You need to make it so you can connect to slapd as
somebody with permission to add entries. This is done
through the following two options in the database definition:

E:	rootdn <dn>
E:	rootpw <passwd>

These options specify a DN and password that can be used
to authenticate as the "superuser" entry of the database (i.e.,
the entry allowed to do anything). The DN and password
specified here will always work, regardless of whether the
entry named actually exists or has the password given. This
solves the chicken-and-egg problem of how to authenticate
and add entries before any entries yet exist.

Finally, you should make sure that the database definition
contains the index definitions you want:

E: 	index {<attrlist> | default} [pres,eq,approx,sub,none]

For example, to index the cn, sn, uid and objectclass
attributes the following index configuration lines could be
used.

E:	index cn,sn,uid
E:	index objectclass pres,eq
E:	index default none

See Section 4 on the configuration file for more details on
this option. Once you have configured things to your liking,
start up slapd, connect with your LDAP client, and start
adding entries. For example, to add a the organizational entry
followed by a Postmaster entry using the {{I:ldapadd}} tool, you
could create a file called {{EX:/tmp/newentry}} with the contents:


E: dc=OpenLDAP, dc=org
E: objectClass=dcObject
E: objectClass=organization
E: dc=OpenLDAP
E: o=OpenLDAP
E: o=OpenLDAP Project
E: o=OpenLDAP Foundation
E: description=The OpenLDAP Foundation
E: description=The OpenLDAP Project
E:
E: cn=Postmaster, dc=OpenLDAP, dc=org
E: objectClass=organizationalRole
E: cn=Postmaster
E: description=OpenLDAP Postmaster <Postmaster@OpenLDAP.org>

and then use a command like this to actually create the
entry:

E: ldapadd -f /tmp/newentry -D "cn=Manager, dc=OpenLDAP, dc=org" -w secret

The above command assumes that you have set {{EX: rootdn}} to
"cn=Manager, dc=OpenLDAP, dc=org" and {{EX: rootpw}}
to "secret".


H2: Creating a database off-line

The second method of database creation is to do it off-line,
using the index generation tools described below. This
method is best if you have many thousands of entries to
create, which would take an unacceptably long time using
the LDAP method described above. These tools read the
slapd configuration file and an input file containing a text
representation of the entries to add. They produce the LDBM
index files directly. There are several important configuration
options you will want to be sure and set in the config file
database definition first:

E:	suffix <dn>

As described in the preceding section, this option says what
entries are to be held by this database. You should set this
to the DN of the root of the subtree you are trying to create.
For example

E:	suffix "dc=OpenLDAP, dc=org"

You should be sure to specify a directory where the index
files should be created:

E:	directory <directory>

For example:

E:	directory /usr/local/var/openldap

Next, you probably want to increase the size of the in-core
cache used by each open index file. For best performance
during index creation, the entire index should fit in memory. If
your data is too big for this, or your memory too small, you
can still make it pretty big and let the paging system do the
work. This size is set with the following option:

E:	dbcachesize <integer>

For example:

E:	dbcachesize 50000000

This would create a cache 50 MB big, which is pretty big (at
U-M, our database has about 125K entries, and our biggest
index file is about 45 MB). Experiment with this number a bit,
and the degree of parallelism (explained below), to see what
works best for your system. Remember to turn this number
back down once your index files are created and before you
run slapd.

Finally, you need to specify which indexes you want to build.
This is done by one or more index options.

E:	index {<attrlist> | default} [pres,eq,approx,sub,none]

For example:

E:	index cn,sn,uid pres,eq,approx
E:	index default none

This would create presence, equality and approximate
indexes for the cn, sn, and uid attributes, and no indexes for
any other attributes. See the configuration file section for
more information on this option.

H3: The {{EX: ldif2ldbm}} program

Once you've configured things to your liking, you create the
indexes by running the ldif2ldbm program:

E:	ldif2ldbm -i <inputfile> -f <slapdconfigfile>
E:		[-d <debuglevel>] [-j <integer>]
E:		[-n <databasenumber>] [-e <etcdir>]

The arguments have the following meanings:

E:	-i <inputfile>

Specifies the LDIF input file containing the entries to add in
text form (described below in Section 8.3).

E:	-f <slapdconfigfile>

Specifies the slapd configuration file that tells where to
create the indexes, what indexes to create, etc.

E:	-d <debuglevel>

Turn on debugging, as specified by {{EX: <debuglevel>}}. The
debug levels are the same as for slapd (see Section 6.1).

E:	-j <integer>

An optional argument that specifies that at most {{EX: <integer>}}
processes should be started in parallel when building the
indexes. The default is 1. If set to a value greater than one,
{{I: ldif2ldbm}} will create at most that many subprocesses at a
time when building the indexes. A separate subprocess is
created to build each attribute index. Running these
processes in parallel can speed things up greatly, but
beware of creating too many processes, all competing for
memory and disk resources.

E: 	-n <databasenumber>

An optional argument that specifies the configuration file
database for which to build indices. The first database listed
is "1", the second "2", etc. By default, the first ldbm database
in the configuration file is used.

E:	-e <etcdir>

An optional argument that specifies the directory where
{{EX: ldif2ldbm}} can find the other database conversion tools it
needs to execute ({{EX: ldif2index}} and friends). The default is the
installation {{EX: ETCDIR}}.

The next sections describe the programs invoked by
{{I: ldif2ldbm}} when it is building indexes. Normally, these
programs are invoked for you, but occasionally you may
want to invoke them yourself.



H3: The {{EX: ldif2index}} program

Sometimes it may be necessary to create a new attribute
index file without disturbing the rest of the database. This is
possible using the {{EX: ldif2index}} program. {{EX: ldif2index}} is invoked
like this

E: 	ldif2index -i <inputfile> -f <slapdconfigfile>
E:		[-d <debuglevel>] [-n <databasenumber>] <attr>

Where the -i, -f, -d, and -n options are the same as for the
{{I: ldif2ldbm}} program. {{EX: <attr>}} is the attribute to build an index for.
Which indexes are built (e.g., equality, substring, etc.) is
controlled by the corresponding index line in the slapd
configuration file.

You can use the ldbmcat program to create a suitable LDIF
input file from an existing LDBM database.


H3: The {{EX: ldbmcat}} program

The {{EX: ldbmcat}} program is used to convert an {{EX: id2entry}} index
back into its LDIF text format. This can be useful when you
want to make a human-readable backup of your database,
or as an intermediate step in creating a new index using the
{{EX: ldif2index}} program. The program is invoked like this:

E: 	ldbmcat [-n] <filename>

where {{EX: <filename>}} is the name of the {{EX: id2entry}} index file. The
corresponding LDIF output is written to standard output.

The -n option can be used to prevent the printing of entry
IDs in the LDIF format. If you are creating an LDIF format for
use as input to {{EX: ldif2index}} or anything by {{EX: ldif2ldbm}}, you
should not use the -n option (because the entry IDs must
match those already in the id2entry file). If you are just
making a backup of your data, you can use the -n option to
save space.



H3: The {{EX: ldif}} program

The ldif program is used to convert arbitrary data values to
LDIF format. This can be useful when writing a program or
script to create the LDIF file you will feed into the ldif2ldbm
program, or when writing a SHELL backend. ldif takes an
attribute name as an argument, and reads the attribute
value(s) from standard input. It produces the LDIF formatted
attribute line(s) on standard output. The usage is:

E: 	ldif [-b] <attrname>

where {{EX: <attrname>}} is the name of the attribute. Without the
-b option, ldif considers each line of standard input to be a
separate value of the attribute.

The -b option can be used to force ldif to interpret its input
as a single raw binary value. This option is useful when
converting binary data such as a {{EX: jpegPhoto}} or {{EX: audio}}
attribute.


H2: The LDIF text entry format

The LDAP Data Interchange Format (LDIF) is used to
represent LDAP entries in a simple text format. The basic
form of an entry is:

E:	[<id>]
E:	dn: <distinguished name>
E:	<attrtype>: <attrvalue>
E:	<attrtype>: <attrvalue>
E:
E: 	...

where {{EX: <id>}} is the optional entry ID (a positive decimal
number). Normally, you would not supply the {{EX: <id>}}, allowing
the database creation tools to do that for you. The ldbmcat
program, however, produces an LDIF format that includes
{{EX: <id>}} so that new indexes created will be consistent.

A line may be continued by starting the next line with a
single space or tab character. e.g.,

E:	dn: cn=Barbara J Jensen, dc=OpenLDAP, dc=org

Multiple attribute values are specified on separate lines. e.g.,

E:	cn: Barbara J Jensen
E:	cn: Babs Jensen

If an {{EX: <attrvalue>}} contains a non-printing character, or
begins with a space or a colon `:', the {{EX: <attrtype>}} is followed
by a double colon and the value is encoded in base 64
notation. e.g., the value " begins with a space" would be
encoded like this:

E:	cn:: IGJlZ2lucyB3aXRoIGEgc3BhY2U=

Multiple entries within the same LDIF file are separated by
blank lines. Here's an example of an LDIF file containing
three entries.

E:	dn: cn=Barbara J Jensen, dc=OpenLDAP, dc=org
E:	cn: Barbara J Jensen
E:	cn: Babs Jensen
E:	objectclass: person
E:	sn: Jensen
E:
E:	dn: cn=Bjorn J Jensen, dc=OpenLDAP, dc=org
E:	cn: Bjorn J Jensen
E:	cn: Bjorn Jensen
E:	objectclass: person
E:	sn: Jensen
E:
E:	dn: cn=Jennifer J Jensen, dc=OpenLDAP, dc=org
E:	cn: Jennifer J Jensen
E:	cn: Jennifer Jensen
E:	objectclass: person
E:	sn: Jensen
E:	jpegPhoto:: /9j/4AAQSkZJRgABAAAAAQABAAD/2wBDABALD
E:	A4MChAODQ4SERATGCgaGBYWGDEjJR0oOjM9PDkzODdASFxOQ
E:	ERXRTc4UG1RV19iZ2hnPk1xeXBkeFxlZ2P/2wBDARESEhgVG
E:	
E:	...

Notice that the {{EX: jpegPhoto}} in Jennifer Jensen's entry is
encoded using base 64. The {{EX: ldif}} program (described in
Section 8.2.6) can be used to produce the LDIF format.

Note: Trailing spaces are not trimmed from values in an
LDIF file. Nor are multiple internal spaces compressed. If
you don't want them in your data, don't put them there.



H2: The LDBM database format

In normal operation, it is not necessary for you to know much
about the LDBM database format. If you are going to use the
ldbmtest program to look at or alter the database, or if you
want a deeper understanding of how indexes are maintained,
some knowledge of how it works could be useful. This
section gives an overview of the database format and how
slapd makes use of it.



H3: Overview

The LDBM database works by assigning a compact
four-byte unique identifier to each entry in the database. It
uses this identifier to refer to entries in indexes. The
database consists of one main index file, called id2entry,
which maps from an entry's unique identifier (EID) to a text
representation of the entry itself. Other index files are
maintained, for each indexed attribute for example, that map
values people are likely to search on to lists of EIDs.

Using this simple scheme, many LDAP queries can be
answered efficiently. For example, to answer a search for
entries with a surname of "Jensen", slapd would first consult
the surname attribute index, look up the value "Jensen" and
retrieve the corresponding list of EIDs. Next, slapd would
look up each EID in the id2entry index, retrieve the
corresponding entry, convert it from text to LDAP format, and
return it to the client.

The following sections give a very brief overview of each
type of index and what it contains. For more detailed
information see the paper "An X.500 and LDAP Database:
Design and Implementation," available in postscript format
from
{{URL:ftp://terminator.rs.itd.umich.edu/ldap/papers/xldbm.ps}}


H3: Attribute index format

The LDBM backend will maintain one index file for each
attribute it is asked to index. Several sets of keys must
coexist in this file (e.g., keys for equality and approximate
equality), so the keys are prefixed with a character to ensure
uniqueness. The prefixes are given in the table below

E:	= equality keys
E:	~ approximate equality keys
E:	* substring equality keys
E:	\ continuation keys

Key values are also normalized (e.g., converted to upper
case for case ignore attributes). So, for example, to look up
the surname equality value in the example above using the
ldbmtest program, you would look up the value "{{EX: =JENSEN}}".

Substring indexes are maintained by generating all possible
N-character substrings for a value (N is 3 by default). These
substrings are then stored in the attribute index, prefixed by
"*". Additional anchors of "^" and "$" are added at the
beginning and end of words. So, for example the surname of
Jensen would cause the following keys to be entered in the
index: {{EX: ^JE, JEN, ENS, NSE, SEN, EN$}}.

Approximate values are handled in a similar way, with
phonetic codes being generated for each word in a value
and then stored in the index, prefixed by "~".

Large blocks in the index are split into smaller ones. The
smaller blocks are accessed through a level of indirection
provided by the original block. They are stored in the index
using the continuation key prefix of "\".



H3: Other indexes

In addition to the {{EX: id2entry}} and attribute indexes, LDBM
maintains a number of other indexes, including the {{EX: dn2id}}
index and the {{EX: id2children}} index. These indexes provide the
mapping between a DN and the corresponding EID, and the
mapping between an EID and the EIDs of the corresponding
entry's children, respectively.

The {{EX: dn2id}} index stores normalized DNs as keys. The data
stored is the corresponding EID.

The {{EX: id2children}} index stores EIDs as keys. The data stored
is a list of EIDs, just as for the attribute indexes.