8. 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.

8.1 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:

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

suffix "o=University of Michigan, c=US"

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

directory <directory>

For example:

directory /usr/local/umich-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:

rootdn <dn>

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:

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.

index cn,sn,uid

index objectclass pres,eq

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 U of M entry followed by a Postmaster entry using the ldapadd tool, you could create a file called /tmp/newentry with the contents:

o=University of Michigan, c=US
objectClass=organization
o=University of Michigan
description=University of Michigan at Ann Arbor
cn=Postmaster, o=University of Michigan, c=US
objectClass=organizationalRole
cn=Postmaster
description=U of M postmaster - postmaster@umich.edu
and then use a command like this to actually create the entry:
ldapadd -f /tmp/newentry -D "cn=Manager, o=University of Michigan, c=US" -w secret
The above command assumes that you have set rootdn to "cn=Manager, o=University of Michigan, c=US" and rootpw to "secret".

8.2 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:

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

suffix "o=University of Michigan, c=US"

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

directory <directory>

For example:

directory /usr/local/umich-slapd

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:

dbcachesize <integer>

For example:

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.

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

For example:

index cn,sn,uid pres,eq,approx

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.

8.2.1 The ldif2ldbm program

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

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

The arguments have the following meanings:

-i <inputfile>

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

-f <slapdconfigfile>

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

-d <debuglevel>

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

-j <integer>

An optional argument that specifies that at most <integer> processes should be started in parallel when building the indexes. The default is 1. If set to a value greater than one, 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.

-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 <etcdir>

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

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

8.2.2 The 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 ldif2index program. ldif2index is invoked like this

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

Where the -i, -f, -d, and -n options are the same as for the ldif2ldbm program. <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.

8.2.3 The ldif2id2entry program

The ldif2id2entry program is normally invoked from ldif2ldbm. It is used to convert an LDIF text file into an id2entry index. It is unlikely that you would need to invoke it yourself, but if you do it works like this

ldif2id2entry -i <inputfile> -f <slapdconfigfile>
[-d <debuglevel>] [-n <databasenumber>]

The arguments are the same as for the ldif2ldbm program.

8.2.4 The ldif2id2children program

The ldif2id2children program is normally invoked from ldif2ldbm. It is used to convert an LDIF text file into id2children and dn2id indexes. Occasionally, it may be necessary to run this program yourself, for example if one of these indexes has become corrupted. ldif2id2children is invoked like this

ldif2id2children -i <inputfile> -f <slapdconfigfile>
[-d <debuglevel>] [-n <databasenumber>]

The arguments are the same as for the ldif2ldbm program. You can use the ldbmcat program to create a suitable LDIF input file from an existing LDBM database.

8.2.5 The ldbmcat program

The ldbmcat program is used to convert an 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 ldif2index program. The program is invoked like this:

ldbmcat [-n] <filename>

where <filename> is the name of the 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 ldif2index or anything by 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.

8.2.6 The 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:

ldif [-b] <attrname>

where <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 jpegPhoto or audio attribute.

8.3 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:
[<id>]
dn: <distinguished name>
<attrtype>: <attrvalue>
<attrtype>: <attrvalue>
...
where <id> is the optional entry ID (a positive decimal number). Normally, you would not supply the <id>, allowing the database creation tools to do that for you. The ldbmcat program, however, produces an LDIF format that includes <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.,

dn: cn=Barbara J Jensen, o=University of Michi
gan, c=US
Multiple attribute values are specified on separate lines. e.g.,
cn: Barbara J Jensen
cn: Babs Jensen
If an <attrvalue> contains a non-printing character, or begins with a space or a colon `:', the <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:
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.
dn: cn=Barbara J Jensen, o=University of Michi
gan, c=US
cn: Barbara J Jensen
cn: Babs Jensen
objectclass: person
sn: Jensen

dn: cn=Bjorn J Jensen, o=University of Michi
gan, c=US
cn: Bjorn J Jensen
cn: Bjorn Jensen
objectclass: person
sn: Jensen

dn: cn=Jennifer J Jensen, o=University of Michi
gan, c=US
cn: Jennifer J Jensen
cn: Jennifer Jensen
objectclass: person
sn: Jensen
jpegPhoto:: /9j/4AAQSkZJRgABAAAAAQABAAD/2wBDABALD
A4MChAODQ4SERATGCgaGBYWGDEjJR0oOjM9PDkzODdASFxOQ
ERXRTc4UG1RV19iZ2hnPk1xeXBkeFxlZ2P/2wBDARESEhgVG
...

Notice that the jpegPhoto in Jennifer Jensen's entry is encoded using base 64. The 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.

8.4 Converting from QUIPU EDB format to LDIF format

If you have directory data that is or was held in a QUIPU DSA (available as part of the ISODE package), you will want to convert the EDB files used by QUIPU into an LDIF file. The edb2ldif program is provided to do most of the conversion for you. Once you have an LDIF file, you should follow the steps outlined in section 6.2 above to build an LDBM database for slapd.

8.4.1 The edb2ldif program

The edb2ldif program is invoked like this:
edb2ldif [-d] [-v] [-r] [-o] [-b <basedn>]
[-a <addvalsfile>] [-f <fileattrdir>]
[-i <ignoreattr...>] [<edbfile...>]
The LDIF data is written to standard output. The arguments have the following meanings:

-d

This option enables some debugging output on standard error.
-v
Enable verbose mode that writes status information to standard error, such as which EDB file is being processed, how many entries have been converted so far, etc.
-r
Recurse through child directories, processing all EDB files found.
-o
Cause local .add file definitions to override the global addfile (see -a below)
-b <basedn>
Specify the Distinguished Name that all EDB file entries appear below.
-a <addvalsfile>
The LDIF information contained in this file will be appended to each entry.
-f <fileattrdir>
Specify a single directory where all file-based attributes (typically sounds and images) can be found. If this option is not given, file attributes are assumed to be located in the same directory as the EDB file that refers to them.
-i <ignoreattr>
Specify an attribute that should not be converted. You can include as many -i flags as necessary.
<edbfile>
Specify a particular EDB file (or files) to read data from. By default, the EDB.root (if it exists) and EDB files in the current directory are used.
When edb2ldif is invoked, it will also look for files named .add in the directories where EDB files are found and append the contents of the .add file to each entry. Typically, this feature is used to include inherited attribute values (e.g., objectClass) that do not appear in the EDB files.

8.4.2 Step-by-step EDB to LDIF conversion

The basic steps to follow when converting your EDB format data to an LDIF file are:
1. Locate the directory at the top of the EDB file hierarchy that your QUIPU DSA masters. The EDB file located there should contain the entries for the first level of your organization or organizational unit. If you are using an indexed database with QUIPU, you may need to create EDB files from your index files (using the synctree or qb2edb tools).

2. If you do not have a file named EDB.root in the same directory that contains your organizational or organizational unit entry, create it now by hand. Its contents should look something like this:

MASTER
000001

o=University of Michigan
objectClass= top & organization & domainRelatedObject &\ quipuObject & quipuNonLeafObject
l= Ann Arbor, Michigan
st= Michigan
o= University of Michigan & UMICH & UM & U-M & U of M
description= The University of Michigan at Ann Arbor
associatedDomain= umich.edu
masterDSA= c=US@cn=Woolly Monkey

3. (Optional) Create a global add file and/or local .add files to take care of adding any attribute values that do not appear in the EDB files. For example, if all entries in a particular EDB are person entries and you want to add the appropriate objectClass attribute value for them, create a file called .add in the same directory as the person EDB that contains the single line:

objectClass: person

4. Run the edb2ldif program to do the actual conversion. Make sure you are in the directory that contains the root of the EDB hierarchy (the one where the EDB.root file resides). Include a -b flag with a base DN one level above your organizational entry, and include -i flags to ignore any attributes that are not useful to slapd. E.g., the command:

edb2ldif -v -r -b "c=US" -i iattr -i acl -i xacl -i sacl
-i lacl -i masterDSA -i slaveDSA > ldif

will convert the entire EDB hierarchy to LDIF format and write the result to a file named ldif. Some attributes that are not useful when running slapd are ignored. The EDB hierarchy is assumed to reside logically below the base DN "c=US".

5. Follow the steps outlined in section 8.2 above to produce an LDBM database from your new LDIF file.

8.5 The ldbmtest program

Occasionally you may find it useful to look at the LDBM database and index files directly (i.e., without going through slapd). The ldbmtest program is provided for this purpose. It gives you raw access to the database itself. ldbmtest should be run line this:
ldbmtest [-d <debuglevel>] [-f <slapdconfigfile>]
The default configuration file in the ETCDIR is used if you don't supply one. By default, ldbmtest operates on the last database listed in the config file. You can specify an alternate database, or see the current database with the following commands.
b specify an alternate backend database
B print out the current backend database
The b command will prompt you for the suffix associated with the database you want. The database you select can be viewed and modified using a set of two-letter commands. The first letter selects the command function to perform. Possible commands and their meanings are as follows.
l lookup (do not follow indirection)
L lookup (follow indirection)
t traverse and print keys and data
T traverse and print keys only
x delete an index item
e edit an index item
a add an index item
c create an index file
i insert an entry into an index item
The second letter indicates which index the command applies to. The possible index selections are as follows.
c id2children index
d dn2id index
e id2entry index
f arbitrary file name
i attribute index
Each command may require additional arguments which ldbmtest will prompt you for.

To exit ldbmtest, type control-D or control-C.

Note that this is a very raw interface originally developed when testing the database format. It is provided and minimally documented here for interested parties, but it is not meant to be used by the inexperienced. See the next section for a brief description of the LDBM database format.

8.6 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.

8.6.1 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

ftp://terminator.rs.itd.umich.edu/ldap/papers/xldbm.ps

8.6.2 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
= equality keys
~ approximate equality keys
* substring equality keys
\ 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 "=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 "$" are added at the beginning and end of words. So, for example the surname of Jensen would cause the following keys to be entered in the index: ^JE, JEN, ENS, NSE, SEN, EN$.

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 "\".

8.6.3 Other indexes

In addition to the id2entry and attribute indexes, LDBM maintains a number of other indexes, including the dn2id index and the 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 dn2id index stores normalized DNs as keys. The data stored is the corresponding EID.

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

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