Exim Specification - 4. Building and installing Exim

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# 4. Building and installing Exim

## 4.1 Unpacking

Exim is distributed as a gzipped or bzipped tar file which, when upacked, creates a directory with the name of the current release (for example, ``exim-3.20'`) into which the following files are placed:

    `CHANGES'        contains a reference to where changes are documented

    `LICENCE'        the GNU General Public Licence
    `Makefile'       top-level make file
    `NOTICE'         conditions for the use of Exim
    `README'         list of files, directories and simple build instructions

Other files whose names begin with ``README'` may also be present. The following subdirectories are created:

    `OS'             OS-specific files
    `doc'            documentation files
    `exim_monitor'   source files for the Exim monitor
    `scripts'        scripts used in the build process
    `src'            remaining source files
    `util'           independent utilities

Some utilities are contained in the ``src'` directory, and are built with the Exim binary; those distributed in the ``util'` directory are things like the log file analyser, which do not depend on any compile-time configuration.

## 4.2 Multiple machine architectures and operating systems

The building process for Exim is arranged to make it easy to build binaries for a number of different architectures and operating systems from the same set of source files. Compilation does not take place in the ``src'` directory. Instead, a build directory is created for each architecture and operating system. Symbolic links to the sources are installed in this directory, which is where the actual building takes place.

In most cases, Exim can discover the machine architecture and operating system for itself, but the defaults can be overridden if necessary.

## 4.3 DBM libraries

Licensed versions of Unix normally contain a library of DBM functions operating via the `ndbm' interface, and this is what Exim expects by default. Free versions of Unix seem to vary in what they contain as standard. In particular, some versions of Linux have no default DBM library, and different distributors have chosen to bundle different libraries with their packaged versions. However, the more recent releases seem to have standardised on the Berkeley DB library.

Different DBM libraries have different conventions for naming the files they use. When a program opens a file called ``dbmfile'`, there are four possibilities:

1. A traditional ndbm implementation, such as that supplied as part of Solaris 2, operates on two files called ``dbmfile.dir'` and ``dbmfile.pag'`.
2. The GNU library, gdbm, operates on a single file, but makes two different hard links to it with names ``dbmfile.dir'` and ``dbmfile.pag'`.
3. The Berkeley DB package, if called via its ndbm compatibility interface, operates on a single file called ``dbmfile.db'`, but otherwise looks to the programmer exactly the same as the traditional ndbm implementation.
4. If the Berkeley package is used in its native mode, it operates on a single file called ``dbmfile'`; the programmer's interface is somewhat different to the traditional ndbm interface.
5. Yet another DBM library, called tdb, has become available from

       http://download.sourceforge.net/tdb

   It has its own interface, and also operates on a single file.

Exim and its utilities can be compiled to use any of these interfaces. By default it assumes an interface of type (1), though some operating system configuration files default to assuming (4). In order to use the Berkeley DB package in native mode, it is necessary to set USE_DB in an appropriate configuration file, and to use tdb you must set USE_TDB. It may also be necessary to set DBMLIB, as in one of these lines:

    DBMLIB = -ldb
    DBMLIB = -ltdb

To complicate things further, there are now three very different versions of the Berkeley DB package. Version 1.85 has been stable for quite some time, releases 2.x were current for a while, but the latest versions are numbered 3.x. Releases 2 and 3 are very different internally and externally from the 1.85 release. All versions of Berkeley DB can be obtained from

    http://www.sleepycat.com/

but maintenance of version 1.85 has been phased out, and it may not compile on some systems. Maintenance for the 2.x releases will cease shortly. There is further discussion about the various DBM libraries in the file ``doc/dbm.discuss.txt'`.

## 4.4 Pre-building configuration

Before building Exim, a local configuration file that specifies options independent of any operating system has to be created with the name ``Local/Makefile'`. A template for this file is supplied as the file ``src/EDITME'`, and it contains full descriptions of all the option settings therein. If you are building Exim for the first time, the simplest thing to do is to copy ``src/EDITME'` to ``Local/Makefile'`, then read it and edit it appropriately.

Default values are supplied for everything except the settings that specify the locations of the run time configuration file and the directory for holding Exim binaries. These must be given, as Exim will not build without them. There are a few parameters that can be specified either at build time or at run time to enable the same binary to be used on a number of different machines. However, if the locations of Exim's spool directory and log file directory (if not within the spool directory) are fixed, it is recommended that you specify them in ``Local/Makefile'` instead of at run time so that errors detected early in Exim's execution (such as a malformed configuration file) can be logged.

If you are going to build the Exim monitor, a similar configuration process is required. The file ``exim_monitor/EDITME'` must be edited appropriately for your installation and saved under the name ``Local/eximon.conf'`. If you are happy with the default settings described in ``exim_monitor/EDITME'`, ``Local/eximon.conf'` can be empty, but it must exist.

This is all the configuration that is needed in straightforward cases for known operating systems. However, the building process is set up so that it is easy to override options that are set by default or by operating-system-specific configuration files, for example to change the name of the C compiler, which defaults to gcc. See section 4.9 below for details of how to do this.

## 4.5 Including TLS/SSL encryption support

Exim can be built to support encrypted SMTP connections, using the STARTTLS command (RFC 2487). Before you can do this, you must install the OpenSSL library, which Exim uses for this purpose. There is no cryptographic code in Exim itself. Once OpenSSL is installed, you can set

    SUPPORT_TLS = yes
    TLS_LIBS=-lssl -lcrypto

in ``Local/Makefile'`. You may also need to specify the locations of the OpenSSL library and include files. For example:

    SUPPORT_TLS = yes
    TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
    TLS_INCLUDE=-I/usr/local/openssl/include/

You don't need to set TLS_INCLUDE if the relevant directory is already specified in INCLUDE.

## 4.6 Use of tcpwrappers

Exim can be linked with the tcpwrappers library in order to check incoming SMTP calls using the tcpwrappers control files. This may be a convenient alternative to Exim's own checking facilities for installations that are already making use of tcpwrappers for other purposes. To do this, you should set USE_TCP_WRAPPERS in ``Local/Makefile'`, arrange for the file ``tcpd.h'` to be available at compile time, and also ensure that the library ``libwrap.a'` is available at link time, typically by including -lwrap in EXTRALIBS_EXIM. For example, if tcpwrappers is installed in ``/usr/local'`, you might have

    USE_TCP_WRAPPERS=yes
    CFLAGS=-O -I/usr/local/include
    EXTRALIBS_EXIM=-L/usr/local/lib -lwrap

in ``Local/Makefile'`. The name to use in the tcpwrappers control files is `exim'. For example, the line

    exim : LOCAL  192.168.0.  .friendly.domain

in your ``/etc/hosts.allow'` file allows connections from the local host, from the subnet 192.168.0.0/24, and from all hosts in friendly.domain. All other connections are denied. Consult the tcpwrappers documentation for further details.

## 4.7 Including support for IPv6

Exim contains code for use on systems that have IPv6 support. Setting HAVE_IPV6=YES in ``Local/Makefile'` causes the IPv6 code to be included; it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems where the IPv6 support is not fully integrated into the normal include and library files.

## 4.8 The building process

Once ``Local/Makefile'` (and ``Local/eximon.conf'`, if required) have been created, run make at the top level. It determines the architecture and operating system types, and creates a build directory if one does not exist. For example, on a Sun system running Solaris 2.5.1, the directory ``build-SunOS5-5.5.1-sparc'` is created. Symbolic links to relevant source files are installed in the build directory.

If this is the first time make has been run, it calls a script which builds a make file inside the build directory, using the configuration files from the ``Local'` directory. The new make file is then passed to another instance of make which does the real work, building a number of utility scripts, and then compiling and linking the binaries for the Exim monitor (if configured), a number of utilities, and finally Exim itself. The command make makefile can be used to force a rebuild of the make file in the build directory, should this ever be necessary.

If you have problems building Exim, check for any comments there may be in the ``README'` file concerning your operating system, and also take a look at the FAQ, where some common problems are covered.

## 4.9 Overriding build-time options for Exim

The main make file that is created at the beginning of the building process consists of the concatenation of a number of files which set configuration values, followed by a fixed set of make instructions. If a value is set more than once, the last setting overrides any previous ones. This provides a convenient way of overriding defaults. The files that are concatenated are, in order:

    OS/Makefile-Default
    OS/Makefile-<ostype>
    Local/Makefile
    Local/Makefile-<ostype>
    Local/Makefile-<archtype>
    Local/Makefile-<ostype>-<archtype>
    OS/Makefile-Base

where <ostype> is the operating system type and <archtype> is the architecture type. ``Local/Makefile'` is required to exist, and the building process fails if it is absent. The other three ``Local'` files are optional, and are often not needed.

The values used for <ostype> and <archtype> are obtained from scripts called ``scripts/os-type'` and ``scripts/arch-type'` respectively. If either of the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their values are used, thereby providing a means of forcing particular settings. Otherwise, the scripts try to get values from the uname command. If this fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number of ad hoc transformations are then applied, to produce the standard names that Exim expects. You can run these scripts directly from the shell in order to find out what values are being used on your system.

``OS/Makefile-Default'` contains comments about the variables that are set therein. Some (but not all) are mentioned below. If there is something that needs changing, review the contents of this file and the contents of the make file for your operating system (``OS/Makefile-<ostype>'`) to see what the default values are.

If you need to change any of the values that are set in ``OS/Makefile-Default'` or in ``OS/Makefile-<ostype>'`, or to add any new definitions, do so by putting the new values in an appropriate ``Local'` file. For example, to specify that the C compiler is called cc rather than gcc when compiling in the OSF1 operating system, and that it is to be to be called with the flag -std1, create a file called ``Local/Makefile-OSF1'` containing the lines

    CC=cc
    CFLAGS=-std1

This makes it easy to transfer your configuration settings to new versions of Exim simply by copying the contents of the ``Local'` directory.

Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file lookup, but not all systems have these components installed, so the default is not to include the relevant code in the binary. All the different kinds of file and database lookup that Exim supports are implemented as separate code modules which are included only if the relevant compile-time options are set. In the case of LDAP, NIS, and NIS+, the settings for ``Local/Makefile'` are:

    LOOKUP_LDAP=yes
    LOOKUP_NIS=yes
    LOOKUP_NISPLUS=yes

and similar settings apply to the other lookup types. In most cases the relevant include files and interface libraries need to be installed before compiling Exim. However, in the case of cdb, which is included in the binary only if

    LOOKUP_CDB=yes

is set, the code is entirely contained within Exim, and no external include files or libraries are required.

When a lookup type is not included in the binary, attempts to configure Exim to use it cause configuration errors.

Exim can be linked with an embedded Perl interpreter, allowing Perl subroutines to be called during string expansion. To enable this facility,

    EXIM_PERL=perl.o

must be defined in ``Local/Makefile'`. Details of this facility are given in chapter 10.

The location of the X11 libraries is something that varies a lot between operating systems, and of course there are different versions of X11 to cope with. The following three variables are set in ``OS/Makefile-Default'`:

    X11=/usr/X11R5
    XINCLUDE=-I$(X11)/include
    XLFLAGS=-L$(X11)/lib

These are overridden in some of the operating-system configuration files. For example, in ``OS/Makefile-SunOS5'` there is

    X11=/usr/openwin
    XINCLUDE=-I$(X11)/include
    XLFLAGS=-L$(X11)/lib -R$(X11)/lib

If you need to override the default setting for your operating system, place a definition of all three of these variables into your ``Local/Makefile-<ostype>'` file.

If you need to add any extra libraries to the link steps, these can be put in a variable called EXTRALIBS, which appears in all the link commands, but by default is not defined. In contrast, EXTRALIBS_EXIM is used only on the command for linking the main Exim binary, and not for any associated utilities. There is also DBMLIB, which appears in the link commands for binaries that use DBM functions (see also section 4.3). Finally, there is EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor binary, and which can be used, for example, to include additional X11 libraries.

Another variable which is not normally defined is STDERR_FILE. This defines a file to which debugging output is written if the -df flag is set, and is of use when running Exim under inetd.

Yet another variable which should not normally be needed is ERRNO_QUOTA. Exim needs to know which error the operating system gives when writing to a file fails because the user is over quota. POSIX specifies an error called EDQUOT and this is present in the latest versions of all the systems Exim has been ported to at the time of writing. However, it is not present in earlier versions of SunOS5, which use ENOSPC instead. The code of Exim defaults to using EDQUOT if it is defined, and ENOSPC otherwise. You should set ERRNO_QUOTA only if your system uses some completely different error code.

The make file copes with rebuilding Exim correctly if any of the configuration files are edited. However, if an optional configuration file is deleted, it is necessary to touch the associated non-optional file (that is, ``Local/Makefile'` or ``Local/eximon.conf'`) before rebuilding.

## 4.10 OS-specific header files

The ``OS'` directory contains a number of files with names of the form ``os.h-<ostype>'`. These are system-specific C header files that should not normally need to be changed. There is a list of macro settings that are recognized in the file ``OS/os.configuring'`, which should be consulted if you are porting Exim to a new operating system.

## 4.11 Overriding build-time options for the monitor

A similar process is used for overriding things when building the Exim monitor, where the files that are involved are

    OS/eximon.conf-Default
    OS/eximon.conf-<ostype>
    Local/eximon.conf
    Local/eximon.conf-<ostype>
    Local/eximon.conf-<archtype>
    Local/eximon.conf-<ostype>-<archtype>

As with Exim itself, the final three files need not exist, and in this case the ``OS/eximon.conf-<ostype>'` file is also optional. The default values in ``OS/eximon.conf-Default'` can be overridden dynamically by setting environment variables of the same name, preceded by EXIMON_. For example, setting EXIMON_LOG_DEPTH in the environment overrides the value of LOG_DEPTH at run time.

## 4.12 Installing commands and scripts

The script ``scripts/exim_install'` copies binaries and utility scripts into the directory whose name is specified by the BIN_DIRECTORY setting in ``Local/Makefile'`. Files are copied only if they are newer than any versions already in the binary directory, and old versions are renamed by adding the suffix ``.O'` to their names.

The command make install runs the exim_install script with no arguments. It can be run independently with arguments specifying which files are to be copied, from within a build directory. For example,

    (cd build-SunOS5-sparc; ../scripts/exim_install exim)

copies just the main binary file. The main exim binary is required to be owned by root and setuid, for normal configurations. In some special cases (for example, if a host is doing no local deliveries) is is possible to run Exim in other ways. If the binary is run by a root process, the effect is the same as if it were setuid root. The install script tries to set root as the owner of the main binary, and to make it setuid. It should therefore normally be run as root. If you want to see what the script will do before running it for real, use the -n option (for which root is not needed):

    (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)

Exim's run time configuration file is named by the CONFIGURE_FILE setting in ``Local/Makefile'`. If this file does not exist, the default configuration file ``src/configure.default'` is copied there by the installation script. If a run time configuration file already exists, it is left alone. The default configuration uses the local host's name as the only local domain, and is set up to do local deliveries into the shared directory ``/var/mail'`, running as the local user. Aliases in ``/etc/aliases'` and ``.forward'` files in users' home directories are supported, but no NIS or NIS+ support is configured. Remote domains are routed using the DNS, with delivery over SMTP.

## 4.13 Installing info documentation

Not all systems use the GNU info system for documentation, and for this reason, the Texinfo source of Exim's documentation is not included in the main distribution. Instead it is available separately from the ftp site (see section 1.2).

If you have defined INFO_DIRECTORY in ``Local/Makefile'` and the Texinfo source of the documentation is found in the source tree, running make install automatically builds the info files and installs them.

## 4.14 Setting up the spool directory

When it starts up, Exim tries to create its spool directory if it does not exist. If a specific Exim uid and gid are specified, these are used for the owner and group of the spool directory. Sub-directories are automatically created in the spool directory as necessary.

## 4.15 Testing

Having installed Exim, you can check that the run time configuration file is syntactically valid by running the command

    exim -bV

If there are any errors in the configuration file, Exim will output error messages. Otherwise it just outputs the version number and build date. Some simple routing tests can be done by using the address testing option. For example,

    exim -v -bt <local username>

should verify that it recognizes a local mailbox, and

    exim -v -bt <remote address>

a remote one. Then try getting it to deliver mail, both locally and remotely. This can be done by passing messages directly to Exim, without going through a user agent. For example:

    exim postmaster@your.domain
    From: user@your.domain
    To: postmaster@your.domain
    Subject: Testing Exim

    This is a test message.
    ^D

If you encounter problems, look at Exim's log files (mainlog and paniclog) to see if there is any relevant information there. Another source of information is running Exim with debugging turned on, by specifying the -d option. The larger the number after -d (up to 9), the more information is output. With -d2, for example, the sequence of directors or routers that process an address is output. If there's a message stuck on Exim's spool, you can force a delivery with debugging turned on by a command of the form

    exim -d9 -M <message-id>

One specific problem that has shown up on some sites is the inability to do local deliveries into a single shared mailbox directory that does not have the `sticky bit' set on it. By default, Exim tries to create a lock file before writing to a mailbox file, and if it cannot create the lock file, the delivery is deferred. You can get round this either by setting the `sticky bit' on the directory, or by setting a specific group for local deliveries and allowing that group to create files in the directory (see the comments above the local_delivery transport in the default configuration file). Another approach is to configure Exim not to use lock files, but just to rely on fcntl() locking instead. However, you should do this only if all user agents also use fcntl() locking. For further discussion of locking issues, see chapter 15.

One thing that cannot be tested on a system that is already running a mailer is the receipt of incoming SMTP mail on the standard SMTP port. However, the -oX option can be used to run an Exim daemon that listens on some other port, or inetd can be used to do this. The -bh option can be used to check out any policy controls on incoming SMTP mail.

Testing a new version on a system that is already running Exim can most easily be done by building a binary with a different CONFIGURE_FILE setting. From within the run time configuration, all other file and directory names that Exim uses can be altered, in order to keep it entirely clear of the production version.

## 4.16 Switching Exim on

Building and installing Exim does not of itself put it in general use. The name by which the system message transfer agent is called by mail user agents is either ``/usr/lib/sendmail'`, or ``/usr/sbin/sendmail'` (depending on the operating system), and it is necessary to make this name point to the exim binary in order to get them to use it. This is normally done by renaming any existing file and making ``/usr/lib/sendmail'` or ``/usr/sbin/sendmail'` a symbolic link to the exim binary. It is a good idea to remove any setuid privilege and executable status from the old MTA. It is then necessary to stop and restart the mailer daemon, if one is running.

## 4.17 Exim on heavily loaded hosts

If you are running Exim on a heavily loaded host you should consider installing a current release of bind (from http://www.isc.org) as caching nameserver, either locally or on a nearby host with a fast network connection. You should also consider enabling Exim's split_spool_directory if you expect to have large numbers of messages awaiting delivery.

## 4.18 Stopping Exim on Solaris

The standard command for stopping the mailer daemon on Solaris is

    /etc/init.d/sendmail stop

If ``/usr/lib/sendmail'` has been turned into a symbolic link, this script fails to stop Exim because it uses the command ps -e and greps the output for the text `sendmail'; this is not present because the actual program name (that is, `exim') is given by the ps command with these options. A fix that appears to work on Solaris 2.5 and above is to change the script so that the ps command reads

    ps -e -o pid,comm

which causes the name by which the daemon was started (that is, ``/usr/lib/sendmail'`) to be output. However, this fails if the daemon has been restarted with SIGHUP because Exim restarts itself using the real file name. A better solution is to replace the line that finds the process id with something like

    pid=`cat /var/spool/exim/exim-daemon.pid`

to obtain the daemon's pid directly from the file that Exim saves it in. See the description of the -bd option for details of where Exim writes the daemon's process id file.

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