Ejabberd Installation and Operation Guide

Alexey Shchepin
mailto:alexey@sevcom.net
xmpp:aleksey@jabber.ru

July 12, 2003



Table of Contents

1  Introduction

ejabberd is a Free and Open Source fault-tolerant distributed Jabber server. It is writen mostly in Erlang.

The main features of ejabberd is:

2  Installation

2.1  Installation Requirements

2.1.1  Unix

To compile ejabberd, you will need the following packages:

2.1.2  Windows

To compile ejabberd in MS Windows environment, you will need the following packages:

2.2  Obtaining

Currently no stable version has been released.

The latest alpha version can be retrieved from CVS.

2.3  Compilation

2.3.1  Unix

./configure
make
TBD

2.3.2  Windows

  1. Install Erlang emulator (for example, into C:\Program Files\erl5.1.2).
  2. Install Expat library into C:\Program Files\Expat-1.95.6 directory. Copy file C:\Program Files\Expat-1.95.6\Libs\libexpat.dll to your Windows system directory (for example, C:\WINNT or C:\WINNT\System32)
  3. Install Iconv library into C:\Program Files\GnuWin32 directory. Copy file C:\Program Files\GnuWin32\bin\libiconv-2.dll to your Windows system directory.

    Note: Instead of copying libexpat.dll and libiconv-2.dll to Windows directory, you can add directories C:\Program Files\Expat-1.95.6\Libs and C:\Program Files\GnuWin32\bin to PATH environment variable.
  4. Being in ejabberd\src directory run: 
    configure
nmake -f Makefile.win32
  5. To build MUC, IRC and pub/sub modules run 
    nmake -f Makefile.win32
    in ejabberd\src\mod_muc, ejabberd\src\mod_muc and ejabberd\src\mod_pubsub directories
  6. Edit file ejabberd\src\ejabberd.cfg and run 
    werl -s ejabberd -name ejabberd
  7. Enjoy!
Some recent versions of Erlang distribution it seems have bug in crypto application, so ejabberd could be built but users can't use digest authentication (only plain-text). Also it seems SSL support is broken in Windows distribution of Erlang emulator.

2.4  Starting

To start ejabberd, use the following command: 
erl -name ejabberd -s ejabberd
or 
erl -sname ejabberd -s ejabberd
In second case Erlang node will be identified using only first part of host name, i. e. other Erlang nodes not inside this domain can't contact this node.

To specify path to config file, use command like this: 
erl -sname ejabberd -s ejabberd -ejabberd config \"/etc/ejabberd/ejabberd.cfg\"
To use more than 1024 connections, you will need to set environment variable ERL_MAX_PORTS: 
export ERL_MAX_PORTS=32000
Note that with this value ejabberd will use more memory (approximately 6MB more).

To reduce memory usage, you can set environment variable ERL_FULLSWEEP_AFTER: 
export ERL_FULLSWEEP_AFTER=0
But in this case ejabberd can start to work slower.

3  Configuration

3.1  Initial Configuration

The configuration file is initially loaded the first time ejabberd is executed, when it is parsed and stored in a database. Subsiquently the configuration is loaded from the database and any commands in the configuration file are appended to the entries in the database. The configuration file consists of a sequence of Erlang terms. Parts of lines after `%' sign are ignored. Each term is tuple, where first element is name of option, and other are option values. E. g. if this file does not contain a ``host'' definition, then old value stored in the database will be used.

To override old values stored in the database the following lines can be added in config: 
override_global.
override_local.
override_acls.
With this lines old global or local options or ACLs will be removed before adding new ones.

3.1.1  Host Name

Option hostname defines name of Jabber domain that ejabberd serves. E. g. to use jabber.org domain add following line in config: 
{host, "jabber.org"}.

3.1.2  Access Rules

Access control in ejabberd is performed via Access Control Lists (ACL). The declarations of ACL in config file have following syntax: 
{acl, <aclname>, {<acltype>, ...}}.
<acltype> can be one of following:
all
Matches all JIDs. Example: 
{acl, all, all}.
{user, <username>}
Matches local user with name <username>. Example: 
{acl, admin, {user, "aleksey"}}.
{user, <username>, <server>}
Matches user with JID <username>@<server> and any resource. Example: 
{acl, admin, {user, "aleksey", "jabber.ru"}}.
{server, <server>}
Matches any JID from server <server>. Example: 
{acl, jabberorg, {server, "jabber.org"}}.
{user_regexp, <regexp>}
Matches local user with name that matches <regexp>. Example: 
{acl, tests, {user, "^test[0-9]*$"}}.
{user_regexp, <regexp>, <server>}
Matches user with name that matches <regexp> and from server <server>. Example: 
{acl, tests, {user, "^test", "localhost"}}.
{server_regexp, <regexp>}
Matches any JID from server that matches <regexp>. Example: 
{acl, icq, {server, "^icq\\."}}.
{node_regexp, <user_regexp>, <server_regexp>}
Matches user with name that matches <user_regexp> and from server that matches <server_regexp>. Example: 
{acl, aleksey, {node_regexp, "^aleksey", "^jabber.(ru|org)$"}}.
{user_glob, <glob>}
{user_glob, <glob>, <server>}
{server_glob, <glob>}
{node_glob, <user_glob>, <server_glob>}
This is same as above, but uses shell glob patterns instead of regexp. These patterns can have following special characters:
*
matches any string including the null string.
?
matches any single character.
[...]
matches any of the enclosed characters. Character ranges are specified by a pair of characters separated by a `-'. If the first character after `[' is a `!', then any character not enclosed is matched.
The following ACLs pre-defined:
all
Matches all JIDs.
none
Matches none JIDs.
An entry allowing or denying different services would look similar to this: 
{access, <accessname>, [{allow, <aclname>},
                        {deny, <aclname>},
                        ...
                       ]}.
When a JID is checked to have access to <accessname>, the server sequentially checks if this JID mathes one of the ACLs that are second elements in each tuple in list. If it is matched, then the first element of matched tuple is returned else ``deny'' is returned.

Example: 
{access, configure, [{allow, admin}]}.
{access, something, [{deny, badmans},
                     {allow, all}]}.
Following access rules pre-defined:
all
Always return ``allow''
none
Always return ``deny''

3.1.3  Shapers Configuration

With shapers is possible to bound connection traffic. The declarations of shapers in config file have following syntax: 
{shaper, <shapername>, <kind>}.
Currently implemented only one kind of shaper: maxrate. It have following syntax: 
{maxrate, <rate>}
where <rate> means maximum allowed incomig rate in bytes/second. E. g. to define shaper with name ``normal'' and maximum allowed rate 1000 bytes/s, add following line in config: 
{shaper, normal, {maxrate, 1000}}.

3.1.4  Listened Sockets

Option listen defines list of listened sockets and what services runned on them. Each element of list is a tuple with following elements: Currently three modules are implemented:
ejabberd_c2s
This module serves C2S connections.

The following options are defined:
{access, <access rule>}
This option defines access of users to this C2S port. Default value is ``all''.
{shaper, <access rule>}
This option is like previous, but use shapers instead of ``allow'' and ``deny''. Default value is ``none''.
{ssl, SSLOpts}
This option defines that traffic on this port will be encrypted using SSL. SSL options are the same as described by ``erl -man ssl'' command
ejabberd_s2s_in
This module serves incoming S2S connections.
ejabberd_service
This module serves connections from Jabber services (i. e. that use the jabber:component:accept namespace).
For example, the following configuration defines that C2S connections are listened on port 5222 and 5223 (SSL) and denied for user ``bad'', S2S on port 5269, and that service conference.example.org must be connected to port 8888 with a password ``secret''. Also all users except admins have traffic limit 1000 b/s. 
{acl, blocked, {user, "bad"}}.
{access, c2s, [{deny, blocked},
               {allow, all}]}.
{shaper, normal, {maxrate, 1000}}.
{access, c2s_shaper, [{none, admin},
                      {normal, all}]}.
{listen, [{5222, ejabberd_c2s,     [{access, c2s},
                                    {shaper, c2s_shaper}]},
          {5223, ejabberd_c2s,     [{access, c2s},
                                    {ssl, [{certfile, "/path/to/ssl.pem"}]}]},
          {5269, ejabberd_s2s_in,  []},
          {8888, ejabberd_service,
           [{hosts, ["conference.example.org"], [{password, "secret"}]}]}
         ]}.

3.1.5  Modules

Option modules defines the list of modules that will be loaded after ejabberd startup. Each list element is a tuple where first element is a name of a module and second is list of options to this module. See section A for detailed information on each module.

Example: 
{modules, [
           {mod_register,  []},
           {mod_roster,    []},
           {mod_configure, []},
           {mod_disco,     []},
           {mod_stats,     []},
           {mod_vcard,     []},
           {mod_offline,   []},
           {mod_echo,      [{host, "echo.localhost"}]},
           {mod_private,   []},
           {mod_time,      [{iqdisc, no_queue}]},
           {mod_version,   []}
          ]}.

3.2  Online Configuration and Monitoring

To perform online reconfiguration of ejabberd you will need to have mod_configure loaded (see section A.4). It is also highly recommended to load mod_disco as well (see section A.5), because mod_configure is highly integrated with it. Additionally it is recommended to use a disco- and xdata-capable client such as Tkabber (which was developed synchronously with ejabberd, its CVS version supports most of ejabberd features).

On disco query ejabberd returns following items:

Figure 1: Tkabber Discovery window

3.2.1  Node config: Global Configuration

Under this node the following nodes exists:

Node config/hostname
Via jabber:x:data queries to this node possible to change host name of this ejabberd server. (See figure 2) (Currently this works correctly only after a restart)

Figure 2: Editing of hostname

Node config/acls
Via jabber:x:data queries to this node it is possible to edit ACLs list. (See figure 3)

Figure 3: Editing of ACLs

Node config/access
Via jabber:x:data queries to this node it is possible to edit access rules.

Node config/remusers
Via jabber:x:data queries to this node it is possible to remove users. If removed user is online, then he will be disconnected. Also user-related data (e.g. his roster) is removed (but appropriate module must be loaded).

3.2.2  Node online users: List of Online Users

3.2.3  Node all users: List of Registered Users


Figure 4: Discovery all users

3.2.4  Node outgoing s2s: List of Outgoing S2S connections

3.2.5  Node running nodes: List of Running ejabberd Nodes


Figure 5: Discovery running nodes

3.2.6  Node stopped nodes: List of Stopped Nodes

TBD

4  Distribution

4.1  How it works

A Jabber domain is served by one or more ejabberd nodes. These nodes can be run on different machines that are connected via a network. They all must have the ability to connect to port 4369 of all another nodes, and must have the same magic cookie (see Erlang/OTP documentation, in other words the file ~ejabberd/.erlang.cookie must be the same on all nodes). This is needed because all nodes exchange information about connected users, S2S connections, registered services, etc...

Each ejabberd node have following modules:

4.1.1  Router

This module is the main router of Jabber packets on each node. It routes them based on their destinations domains. It has two tables: local and global routes. First, domain of packet destination searched in local table, and if it found, then the packet is routed to appropriate process. If no, then it searches in global table, and is routed to the appropriate ejabberd node or process. If it does not exists in either tables, then it sent to the S2S manager.

4.1.2  Local Router

This module routes packets which have a destination domain equal to this server name. If destination JID has a non-empty user part, then it routed to the session manager, else it is processed depending on it's content.

4.1.3  Session Manager

This module routes packets to local users. It searches for what user resource packet must be sended via presence table. If this resource is connected to this node, it is routed to C2S process, if it connected via another node, then the packet is sent to session manager on that node.

4.1.4  S2S Manager

This module routes packets to other Jabber servers. First, it checks if an open S2S connection from the domain of the packet source to the domain of packet destination already exists. If it is open on another node, then it routes the packet to S2S manager on that node, if it is open on this node, then it is routed to the process that serves this connection, and if a connection does not exist, then it is opened and registered.

A  Built-in Modules

A.1  Common Options

The following options are used by many modules, so they are described in separate section.

A.1.1  Option iqdisc

Many modules define handlers for processing IQ queries of different namespaces to this server or to user (e. g. to example.org or to user@example.org). This option defines processing discipline of these queries. Possible values are:
no_queue
All queries of namespace with this processing discipline processed immediately. This also means that no other packets can be processed until finished this. Hence this discipline is not recommended if processing of query can take relative many time.
one_queue
In this case created separate queue for processing of IQ queries of namespace with this discipline, and processing of this queue is done in parallel with processing of other packets. This discipline is most recommended.
parallel
In this case for all packets with this discipline spawned separate Erlang process, so all these packets processed in parallel. Although spawning of Erlang process have relatively low cost, this can broke server normal work, because Erlang emulator have limit on number of processes (32000 by default).
Example: 
{modules, [
           ...
           {mod_time,      [{iqdisc, no_queue}]},
           ...
          ]}.

A.1.2  Option host

Some modules may act as services, and wants to have different domain name. This option explicitly defines this name.

Example: 
{modules, [
           ...
           {mod_echo,      [{host, "echo.example.org"}]},
           ...
          ]}.

A.2  mod_register

This module adds support for JEP-0077 (In-Band Registration). There is possible to restrict registration via ``register'' access rule. If this rule returns ``deny'' on requested user name, then registration is not allowed for it.

Options:
iqdisc
jabber:iq:register IQ queries processing discipline.
Example: 
% Deny registration for users with too short name
{acl, shortname, {user_glob, "?"}}.
{acl, shortname, {user_glob, "??"}}.
% Another variant: {acl, shortname, {user_regexp, "^..?$"}}.

{access, register, [{deny, shortname},
                    {allow, all}]}.

{modules, [
           ...
           {mod_register, []},
           ...
          ]}.

A.3  mod_roster

A.4  mod_configure

A.5  mod_disco

This module adds support for JEP-0030 (Service Discovery).

Options:
iqdisc
http://jabber.org/protocol/disco#items and http://jabber.org/protocol/disco#info IQ queries processing discipline.
extra_domains
List of domains that will be added to server items reply
Example: 
{modules, [
           ...
           {mod_disco, [{extra_domains, ["jit.example.com",
                                         "etc.example.com"]}]},
           ...
          ]}.

A.6  mod_stats

This module adds support for JEP-0039 (Statistics Gathering).

Options:
iqdisc
http://jabber.org/protocol/stats IQ queries processing discipline.
TBD about access.

A.7  mod_vcard

A.8  mod_offline

A.9  mod_echo

A.10  mod_private

This module adds support of JEP-0049 (Private XML Storage).

Options:
iqdisc
jabber:iq:private IQ queries processing discipline.

A.11  mod_time

This module answers UTC time on jabber:iq:time queries.

Options:
iqdisc
jabber:iq:time IQ queries processing discipline.

A.12  mod_version

This module answers ejabberd version on jabber:iq:version queries.

Options:
iqdisc
jabber:iq:version IQ queries processing discipline.

B  I18n/L10n

Many modules supports xml:lang attribute inside IQ queries. E. g. on figure 6 (compare it with figure 1) showed reply on following query: 
<iq id='5'
    to='e.localhost'
    type='get'>
  <query xmlns='http://jabber.org/protocol/disco#items'
         xml:lang='ru'/>
</iq>

Figure 6: Discovery result when xml:lang='ru'

This document was translated from LATEX by HEVEA.