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<!DOCTYPE chapter SYSTEM "chapter.dtd">
<chapter>
<header>
<copyright>
<year>2003</year><year>2013</year>
<holder>Ericsson AB. All Rights Reserved.</holder>
</copyright>
<legalnotice>
The contents of this file are subject to the Erlang Public License,
Version 1.1, (the "License"); you may not use this file except in
compliance with the License. You should have received a copy of the
Erlang Public License along with this software. If not, it can be
retrieved online at http://www.erlang.org/.
Software distributed under the License is distributed on an "AS IS"
basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
the License for the specific language governing rights and limitations
under the License.
</legalnotice>
<title>Releases</title>
<prepared></prepared>
<docno></docno>
<date></date>
<rev></rev>
<file>release_structure.xml</file>
</header>
<marker id="releases section"></marker>
<p>This section is to be read with the <c>rel(4)</c>, <c>systools(3)</c>,
and <c>script(4)</c> manual pages in SASL.</p>
<section>
<title>Release Concept</title>
<p>When you have written one or more applications, you might want
to create a complete system with these applications and a
subset of the Erlang/OTP applications. This is called a
<em>release</em>.</p>
<p>To do this, create a
<seealso marker="#res_file">release resource file</seealso> that
defines which applications are included in the release.</p>
<p>The release resource file is used to generate
<seealso marker="#boot">boot scripts</seealso> and
<seealso marker="#pack">release packages</seealso>. A system
that is transferred to and installed at another site is called a
<em>target system</em>. How to use a release package to create a
target system is described in System Principles.</p>
</section>
<section>
<marker id="res_file"></marker>
<title>Release Resource File</title>
<p>To define a release, create a <em>release resource file</em>,
or in short a <c>.rel</c> file. In the file, specify the name and
version of the release, which ERTS version it is based on,
and which applications it consists of:</p>
<code type="none">
{release, {Name,Vsn}, {erts, EVsn},
[{Application1, AppVsn1},
...
{ApplicationN, AppVsnN}]}.</code>
<p><c>Name</c>, <c>Vsn</c>, <c>EVsn</c>, and <c>AppVsn</c> are
strings.</p>
<p>The file must be named <c>Rel.rel</c>, where <c>Rel</c> is a
unique name.</p>
<p>Each <c>Application</c> (atom) and <c>AppVsn</c> is
the name and version of an application included in the release.
The minimal release based on Erlang/OTP consists of
the Kernel and STDLIB applications, so these
applications must be included in the list.</p>
<p>If the release is to be upgraded, it must also include
the SASL application.</p>
<marker id="ch_rel"></marker>
<p><em>Example: </em> A release of <c>ch_app</c> from
<seealso marker="applications#ch_app">Applications</seealso>
has the following <c>.app</c> file:</p>
<code type="none">
{application, ch_app,
[{description, "Channel allocator"},
{vsn, "1"},
{modules, [ch_app, ch_sup, ch3]},
{registered, [ch3]},
{applications, [kernel, stdlib, sasl]},
{mod, {ch_app,[]}}
]}.</code>
<p>The <c>.rel</c> file must also contain <c>kernel</c>,
<c>stdlib</c>, and <c>sasl</c>, as these applications are required
by <c>ch_app</c>. The file is called <c>ch_rel-1.rel</c>:</p>
<code type="none">
{release,
{"ch_rel", "A"},
{erts, "5.3"},
[{kernel, "2.9"},
{stdlib, "1.12"},
{sasl, "1.10"},
{ch_app, "1"}]
}.</code>
</section>
<section>
<marker id="boot"></marker>
<title>Generating Boot Scripts</title>
<p><c>systools</c> in the SASL application includes tools to
build and check releases. The functions read the <c>rel</c> and
<c>.app</c> files and performs syntax and dependency checks.
The <c>systools:make_script/1,2</c> function is used to generate
a boot script (see System Principles):</p>
<pre>
1> <input>systools:make_script("ch_rel-1", [local]).</input>
ok</pre>
<p>This creates a boot script, both the readable version,
<c>ch_rel-1.script</c>, and the binary version, <c>ch_rel-1.boot</c>,
used by the runtime system.</p>
<list type="bulleted">
<item><c>"ch_rel-1"</c> is the name of the <c>.rel</c> file,
minus the extension.</item>
<item><c>local</c> is an option that means that the directories
where the applications are found are used in the boot script,
instead of <c>$ROOT/lib</c> (<c>$ROOT</c> is the root directory
of the installed release).</item>
</list>
<p> This is a useful way to test a generated boot script locally.</p>
<p>When starting Erlang/OTP using the boot script, all applications
from the <c>.rel</c> file are automatically loaded and started:</p>
<pre>
% <input>erl -boot ch_rel-1</input>
Erlang (BEAM) emulator version 5.3
Eshell V5.3 (abort with ^G)
1>
=PROGRESS REPORT==== 13-Jun-2003::12:01:15 ===
supervisor: {local,sasl_safe_sup}
started: [{pid,<0.33.0>},
{name,alarm_handler},
{mfa,{alarm_handler,start_link,[]}},
{restart_type,permanent},
{shutdown,2000},
{child_type,worker}]
...
=PROGRESS REPORT==== 13-Jun-2003::12:01:15 ===
application: sasl
started_at: nonode@nohost
...
=PROGRESS REPORT==== 13-Jun-2003::12:01:15 ===
application: ch_app
started_at: nonode@nohost</pre>
</section>
<section>
<marker id="pack"></marker>
<title>Creating a Release Package</title>
<p>The <c>systools:make_tar/1,2</c> function takes a <c>.rel</c> file
as input and creates a zipped tar file with the code for the specified
applications, a <em>release package</em>:</p>
<pre>
1> <input>systools:make_script("ch_rel-1").</input>
ok
2> <input>systools:make_tar("ch_rel-1").</input>
ok</pre>
<p>The release package by default contains:</p>
<list type="bulleted">
<item>The <c>.app</c> files</item>
<item>The <c>.rel</c> file</item>
<item>The object code for all applications, structured according
to the
<seealso marker="applications#app_dir">application directory
structure</seealso></item>
<item>The binary boot script renamed to <c>start.boot</c></item>
</list>
<pre>
% <input>tar tf ch_rel-1.tar</input>
lib/kernel-2.9/ebin/kernel.app
lib/kernel-2.9/ebin/application.beam
...
lib/stdlib-1.12/ebin/stdlib.app
lib/stdlib-1.12/ebin/beam_lib.beam
...
lib/sasl-1.10/ebin/sasl.app
lib/sasl-1.10/ebin/sasl.beam
...
lib/ch_app-1/ebin/ch_app.app
lib/ch_app-1/ebin/ch_app.beam
lib/ch_app-1/ebin/ch_sup.beam
lib/ch_app-1/ebin/ch3.beam
releases/A/start.boot
releases/A/ch_rel-1.rel
releases/ch_rel-1.rel</pre>
<p>A new boot script was generated, without
the <c>local</c> option set, before the release package was made.
In the release package, all application directories are placed
under <c>lib</c>. You do not know where the release package
will be installed, so no hard-coded absolute paths are allowed.</p>
<p>The release resource file <c>mysystem.rel</c> is duplicated in
the tar file. Originally, this file was only stored in
the <c>releases</c> directory to make it possible for
the <c>release_handler</c> to extract this file
separately. After unpacking the tar file, <c>release_handler</c>
would automatically copy the file
to <c>releases/FIRST</c>. However, sometimes the tar file is
unpacked without involving the <c>release_handler</c> (for
example, when unpacking the first target system) and the file
is therefore now instead duplicated in the tar file so no manual
copying is necessary.</p>
<p>If a <c>relup</c> file and/or a system configuration file called
<c>sys.config</c> is found, these files are also included in
the release package. See
<seealso marker="release_handling#req">Release Handling</seealso>.</p>
<p>Options can be set to make the release package include source
code and the ERTS binary as well.</p>
<p>For information on how to install the first target system, using
a release package, see System Principles. For information
on how to install a new release package in an existing system, see
<seealso marker="release_handling">Release Handling</seealso>.</p>
</section>
<section>
<marker id="reldir"></marker>
<title>Directory Structure</title>
<p>The directory structure for the code installed by the release handler
from a release package is as follows:</p>
<code type="none">
$ROOT/lib/App1-AVsn1/ebin
/priv
/App2-AVsn2/ebin
/priv
...
/AppN-AVsnN/ebin
/priv
/erts-EVsn/bin
/releases/Vsn
/bin</code>
<list type="bulleted">
<item><c>lib</c> - Application directories</item>
<item><c>erts-EVsn/bin</c> - Erlang runtime system executables</item>
<item><c>releases/Vsn</c> - <c>.rel</c> file and boot script
<c>start.boot</c>; if present in the release package, <c>relup</c>
and/or <c>sys.config</c></item>
<item><c>bin</c> - Top-level Erlang runtime system executables</item>
</list>
<p>Applications are not required to be located under directory
<c>$ROOT/lib</c>. Several installation directories, which contain
different parts of a system, can thus exist.
For example, the previous example can be extended as follows:</p>
<pre>
$SECOND_ROOT/.../SApp1-SAVsn1/ebin
/priv
/SApp2-SAVsn2/ebin
/priv
...
/SAppN-SAVsnN/ebin
/priv
$THIRD_ROOT/TApp1-TAVsn1/ebin
/priv
/TApp2-TAVsn2/ebin
/priv
...
/TAppN-TAVsnN/ebin
/priv</pre>
<p><c>$SECOND_ROOT</c> and <c>$THIRD_ROOT</c> are introduced as
<c>variables</c> in the call to the <c>systools:make_script/2</c>
function.</p>
<section>
<title>Disk-Less and/or Read-Only Clients</title>
<p>If a complete system consists of disk-less and/or
read-only client nodes, a <c>clients</c> directory is to be
added to the <c>$ROOT</c> directory. A read-only node is
a node with a read-only file system.</p>
<p>The <c>clients</c> directory is to have one subdirectory
per supported client node. The name of each client directory
is to be the name of the corresponding client node. As a
minimum, each client directory is to contain the <c>bin</c> and
<c>releases</c> subdirectories. These directories are used to
store information about installed releases and to appoint the
current release to the client. The <c>$ROOT</c>
directory thus contains the following:</p>
<code type="none">
$ROOT/...
/clients/ClientName1/bin
/releases/Vsn
/ClientName2/bin
/releases/Vsn
...
/ClientNameN/bin
/releases/Vsn</code>
<p>This structure is to be used if all clients are running
the same type of Erlang machine. If there are clients running
different types of Erlang machines, or on different operating
systems, the <c>clients</c> directory can be divided into one
subdirectory per type of Erlang machine. Alternatively, one
<c>$ROOT</c> can be set up per type of machine. For each
type, some of the directories specified for the <c>$ROOT</c>
directory are to be included:</p>
<code type="none">
$ROOT/...
/clients/Type1/lib
/erts-EVsn
/bin
/ClientName1/bin
/releases/Vsn
/ClientName2/bin
/releases/Vsn
...
/ClientNameN/bin
/releases/Vsn
...
/TypeN/lib
/erts-EVsn
/bin
...</code>
<p>With this structure, the root directory for clients of
<c>Type1</c> is <c>$ROOT/clients/Type1</c>.</p>
</section>
</section>
</chapter>
