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authorSiri Hansen <siri@erlang.org>2011-11-25 15:31:55 +0100
committerSiri Hansen <siri@erlang.org>2011-12-01 16:14:56 +0100
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parent08ea3af8528ad0920021ecc230a66eb5ee59bc86 (diff)
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+<?xml version="1.0" encoding="latin1" ?>
+<!DOCTYPE chapter SYSTEM "chapter.dtd">
+
+<chapter>
+ <header>
+ <copyright>
+ <year>2002</year><year>2011</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>Creating a First Target System</title>
+ <prepared>Peter H&ouml;gfeldt</prepared>
+ <responsible></responsible>
+ <docno></docno>
+ <approved></approved>
+ <checked></checked>
+ <date>2002-09-17</date>
+ <rev>A</rev>
+ <file>create_target.xml</file>
+ </header>
+
+ <section>
+ <title>Introduction</title>
+ <p>When creating a system using Erlang/OTP, the most simple way is
+ to install Erlang/OTP somewhere, install the application specific
+ code somewhere else, and then start the Erlang runtime system,
+ making sure the code path includes the application specific code.</p>
+ <p>Often it is not desirable to use an Erlang/OTP system as is. A
+ developer may create new Erlang/OTP compliant applications for a
+ particular purpose, and several original Erlang/OTP applications
+ may be irrelevant for the purpose in question. Thus, there is a
+ need to be able to create a new system based on a given
+ Erlang/OTP system, where dispensable applications are removed,
+ and a set of new applications that are included in the new
+ system. Documentation and source code is irrelevant and is
+ therefore not included in the new system.</p>
+ <p>This chapter is about creating such a system, which we call a
+ <em>target system</em>.</p>
+ <p>In the following sections we consider creating target systems with
+ different requirements of functionality:</p>
+ <list type="bulleted">
+ <item>a <em>basic target system</em> that can be started by
+ calling the ordinary <c>erl</c> script, </item>
+ <item>a <em>simple target system</em> where also code
+ replacement in run-time can be performed, and</item>
+ <item>an <em>embedded target system</em> where there is also
+ support for logging output from the system to file for later
+ inspection, and where the system can be started automatically
+ at boot time. </item>
+ </list>
+ <p>We only consider the case when Erlang/OTP is running on a UNIX
+ system.</p>
+ <p>There is an example Erlang module <c>target_system.erl</c> that
+ contains functions for creating and installing a target system.
+ That module is used in the examples below. The source code of
+ the module is listed at the end of this chapter.</p>
+ </section>
+
+ <section>
+ <title>Creating a Target System</title>
+ <p>It is assumed that you have a working Erlang/OTP system structured
+ according to the OTP Design Principles.</p>
+ <p><em>Step 1.</em> First create a <c>.rel</c> file (see
+ <c>rel(4)</c>) that specifies the <c>erts</c> version
+ and lists all applications that should be included in the new
+ basic target system. An example is the following
+ <c>mysystem.rel</c> file:</p>
+ <code type="none">
+%% mysystem.rel
+{release,
+ {"MYSYSTEM", "FIRST"},
+ {erts, "5.1"},
+ [{kernel, "2.7"},
+ {stdlib, "1.10"},
+ {sasl, "1.9.3"},
+ {pea, "1.0"}]}. </code>
+ <p>The listed applications are not only original Erlang/OTP
+ applications but possibly also new applications that you have
+ written yourself (here examplified by the application
+ <c>pea</c>). </p>
+ <p><em>Step 2.</em> From the directory where the <c>mysystem.rel</c>
+ file reside, start the Erlang/OTP system:</p>
+ <pre>
+os> <input>erl -pa /home/user/target_system/myapps/pea-1.0/ebin</input></pre>
+ <p>where also the path to the <c>pea-1.0</c> ebin directory is
+ provided. </p>
+ <p><em>Step 3.</em> Now create the target system: </p>
+ <pre>
+1> <input>target_system:create("mysystem").</input></pre>
+ <p>The <c>target_system:create/1</c> function does the following:</p>
+ <list type="ordered">
+ <item>Reads the <c>mysystem.rel</c> file, and creates a new file
+ <c>plain.rel</c> which is identical to former, except that it
+ only lists the <c>kernel</c> and <c>stdlib</c> applications. </item>
+ <item>From the <c>mysystem.rel</c> and <c>plain.rel</c> files
+ creates the files <c>mysystem.script</c>,
+ <c>mysystem.boot</c>, <c>plain.script</c>, and
+ <c>plain.boot</c> through a call to
+ <c>systools:make_script/2</c>.</item>
+ <item>
+ <p>Creates the file <c>mysystem.tar.gz</c> by a call to
+ <c>systools:make_tar/2</c>. That file has the following
+ contents:</p>
+ <code type="none">
+erts-5.1/bin/
+releases/FIRST/start.boot
+releases/mysystem.rel
+lib/kernel-2.7/
+lib/stdlib-1.10/
+lib/sasl-1.9.3/
+lib/pea-1.0/ </code>
+ <p>The file <c>releases/FIRST/start.boot</c> is a copy of our
+ <c>mysystem.boot</c>, and a copy of the original
+ <c>mysystem.rel</c> has been put in the <c>releases</c>
+ directory.</p>
+ </item>
+ <item>Creates the temporary directory <c>tmp</c> and extracts the tar file
+ <c>mysystem.tar.gz</c> into that directory. </item>
+ <item>Deletes the <c>erl</c> and <c>start</c> files from
+ <c>tmp/erts-5.1/bin</c>. XXX Why.</item>
+ <item>Creates the directory <c>tmp/bin</c>.</item>
+ <item>Copies the previously creates file <c>plain.boot</c> to
+ <c>tmp/bin/start.boot</c>.</item>
+ <item>Copies the files <c>epmd</c>, <c>run_erl</c>, and
+ <c>to_erl</c> from the directory <c>tmp/erts-5.1/bin</c> to
+ the directory <c>tmp/bin</c>.</item>
+ <item>Creates the file <c>tmp/releases/start_erl.data</c> with the
+ contents "5.1 FIRST".
+ </item>
+ <item>Recreates the file <c>mysystem.tar.gz</c> from the directories
+ in the directory <c>tmp</c>, and removes <c>tmp</c>.</item>
+ </list>
+ </section>
+
+ <section>
+ <title>Installing a Target System</title>
+ <p><em>Step 4.</em> Install the created target system in a
+ suitable directory. </p>
+ <pre>
+2> <input>target_system:install("mysystem", "/usr/local/erl-target").</input></pre>
+ <p>The function <c>target_system:install/2</c> does the following:
+ </p>
+ <list type="ordered">
+ <item>Extracts the tar file <c>mysystem.tar.gz</c> into the target
+ directory <c>/usr/local/erl-target</c>.</item>
+ <item>In the target directory reads the file <c>releases/start_erl.data</c>
+ in order to find the Erlang runtime system version ("5.1").</item>
+ <item>Substitutes <c>%FINAL_ROOTDIR%</c> and <c>%EMU%</c> for
+ <c>/usr/local/erl-target</c> and <c>beam</c>, respectively, in
+ the files <c>erl.src</c>, <c>start.src</c>, and
+ <c>start_erl.src</c> of the target <c>erts-5.1/bin</c>
+ directory, and puts the resulting files <c>erl</c>,
+ <c>start</c>, and <c>run_erl</c> in the target <c>bin</c>
+ directory.</item>
+ <item>Finally the target <c>releases/RELEASES</c> file is created
+ from data in the <c>releases/mysystem.rel</c> file.</item>
+ </list>
+ </section>
+
+ <section>
+ <title>Starting a Target System</title>
+ <p>Now we have a target system that can be started in various ways.</p>
+ <p>We start it as a <em>basic target system</em> by invoking</p>
+ <pre>
+os> <input>/usr/local/erl-target/bin/erl</input></pre>
+ <p>where only the <c>kernel</c> and <c>stdlib</c> applications are
+ started, i.e. the system is started as an ordinary development
+ system. There are only two files needed for all this to work:
+ <c>bin/erl</c> file (obtained from <c>erts-5.1/bin/erl.src</c>)
+ and the <c>bin/start.boot</c> file (a copy of <c>plain.boot</c>).</p>
+ <p>We can also start a distributed system (requires <c>bin/epmd</c>).</p>
+ <p>To start all applications specified in the original
+ <c>mysystem.rel</c> file, use the <c>-boot</c> flag as follows:</p>
+ <pre>
+os> <input>/usr/local/erl-target/bin/erl -boot /usr/local/erl-target/releases/FIRST/start</input></pre>
+ <p>We start a <em>simple target system</em> as above. The only difference
+ is that also the file <c>releases/RELEASES</c> is present for
+ code replacement in run-time to work.</p>
+ <p>To start an <em>embedded target system</em> the shell script
+ <c>bin/start</c> is used. That shell script calls
+ <c>bin/run_erl</c>, which in turn calls <c>bin/start_erl</c>
+ (roughly, <c>start_erl</c> is an embedded variant of
+ <c>erl</c>). </p>
+ <p>The shell script <c>start</c> is only an example. You should
+ edit it to suite your needs. Typically it is executed when the
+ UNIX system boots.</p>
+ <p><c>run_erl</c> is a wrapper that provides logging of output from
+ the run-time system to file. It also provides a simple mechanism
+ for attaching to the Erlang shell (<c>to_erl</c>).</p>
+ <p><c>start_erl</c> requires the root directory
+ (<c>"/usr/local/erl-target"</c>), the releases directory
+ (<c>"/usr/local/erl-target/releases"</c>), and the location of
+ the <c>start_erl.data</c> file. It reads the run-time system
+ version (<c>"5.1"</c>) and release version (<c>"FIRST"</c>) from
+ the <c>start_erl.data</c> file, starts the run-time system of the
+ version found, and provides <c>-boot</c> flag specifying the boot
+ file of the release version found
+ (<c>"releases/FIRST/start.boot"</c>).</p>
+ <p><c>start_erl</c> also assumes that there is <c>sys.config</c> in
+ release version directory (<c>"releases/FIRST/sys.config</c>). That
+ is the topic of the next section (see below).</p>
+ <p>The <c>start_erl</c> shell script should normally not be
+ altered by the user.</p>
+ </section>
+
+ <section>
+ <title>System Configuration Parameters</title>
+ <p>As was pointed out above <c>start_erl</c> requires a
+ <c>sys.config</c> in the release version directory
+ (<c>"releases/FIRST/sys.config"</c>). If there is no such a
+ file, the system start will fail. Hence such a file has to
+ added as well.</p>
+ <p></p>
+ <p>If you have system configuration data that are neither file
+ location dependent nor site dependent, it may be convenient to
+ create the <c>sys.config</c> early, so that it becomes a part of
+ the target system tar file created by
+ <c>target_system:create/1</c>. In fact, if you create, in the
+ current directory, not only the <c>mysystem.rel</c> file, but
+ also a <c>sys.config</c> file, that latter file will be tacitly
+ put in the apropriate directory.</p>
+ </section>
+
+ <section>
+ <title>Differences from the Install Script</title>
+ <p>The above <c>install/2</c> procedure differs somewhat from that
+ of the ordinary <c>Install</c> shell script. In fact, <c>create/1</c>
+ makes the release package as complete as possible, and leave to the
+ <c>install/2</c> procedure to finish by only considering location
+ dependent files.</p>
+ </section>
+
+ <section>
+ <title>Listing of target_system.erl</title>
+ <code type="none"><![CDATA[
+-module(target_system).
+-include_lib("kernel/include/file.hrl").
+-export([create/1, install/2]).
+-define(BUFSIZE, 8192).
+
+%% Note: RelFileName below is the *stem* without trailing .rel,
+%% .script etc.
+%%
+
+%% create(RelFileName)
+%%
+create(RelFileName) ->
+ RelFile = RelFileName ++ ".rel",
+ io:fwrite("Reading file: \"~s\" ...~n", [RelFile]),
+ {ok, [RelSpec]} = file:consult(RelFile),
+ io:fwrite("Creating file: \"~s\" from \"~s\" ...~n",
+ ["plain.rel", RelFile]),
+ {release,
+ {RelName, RelVsn},
+ {erts, ErtsVsn},
+ AppVsns} = RelSpec,
+ PlainRelSpec = {release,
+ {RelName, RelVsn},
+ {erts, ErtsVsn},
+ lists:filter(fun({kernel, _}) ->
+ true;
+ ({stdlib, _}) ->
+ true;
+ (_) ->
+ false
+ end, AppVsns)
+ },
+ {ok, Fd} = file:open("plain.rel", [write]),
+ io:fwrite(Fd, "~p.~n", [PlainRelSpec]),
+ file:close(Fd),
+
+ io:fwrite("Making \"plain.script\" and \"plain.boot\" files ...~n"),
+ make_script("plain"),
+
+ io:fwrite("Making \"~s.script\" and \"~s.boot\" files ...~n",
+ [RelFileName, RelFileName]),
+ make_script(RelFileName),
+
+ TarFileName = io_lib:fwrite("~s.tar.gz", [RelFileName]),
+ io:fwrite("Creating tar file \"~s\" ...~n", [TarFileName]),
+ make_tar(RelFileName),
+
+ io:fwrite("Creating directory \"tmp\" ...~n"),
+ file:make_dir("tmp"),
+
+ io:fwrite("Extracting \"~s\" into directory \"tmp\" ...~n", [TarFileName]),
+ extract_tar(TarFileName, "tmp"),
+
+ TmpBinDir = filename:join(["tmp", "bin"]),
+ ErtsBinDir = filename:join(["tmp", "erts-" ++ ErtsVsn, "bin"]),
+ io:fwrite("Deleting \"erl\" and \"start\" in directory \"~s\" ...~n",
+ [ErtsBinDir]),
+ file:delete(filename:join([ErtsBinDir, "erl"])),
+ file:delete(filename:join([ErtsBinDir, "start"])),
+
+ io:fwrite("Creating temporary directory \"~s\" ...~n", [TmpBinDir]),
+ file:make_dir(TmpBinDir),
+
+ io:fwrite("Copying file \"plain.boot\" to \"~s\" ...~n",
+ [filename:join([TmpBinDir, "start.boot"])]),
+ copy_file("plain.boot", filename:join([TmpBinDir, "start.boot"])),
+
+ io:fwrite("Copying files \"epmd\", \"run_erl\" and \"to_erl\" from \n"
+ "\"~s\" to \"~s\" ...~n",
+ [ErtsBinDir, TmpBinDir]),
+ copy_file(filename:join([ErtsBinDir, "epmd"]),
+ filename:join([TmpBinDir, "epmd"]), [preserve]),
+ copy_file(filename:join([ErtsBinDir, "run_erl"]),
+ filename:join([TmpBinDir, "run_erl"]), [preserve]),
+ copy_file(filename:join([ErtsBinDir, "to_erl"]),
+ filename:join([TmpBinDir, "to_erl"]), [preserve]),
+
+ StartErlDataFile = filename:join(["tmp", "releases", "start_erl.data"]),
+ io:fwrite("Creating \"~s\" ...~n", [StartErlDataFile]),
+ StartErlData = io_lib:fwrite("~s ~s~n", [ErtsVsn, RelVsn]),
+ write_file(StartErlDataFile, StartErlData),
+
+ io:fwrite("Recreating tar file \"~s\" from contents in directory "
+ "\"tmp\" ...~n", [TarFileName]),
+ {ok, Tar} = erl_tar:open(TarFileName, [write, compressed]),
+ {ok, Cwd} = file:get_cwd(),
+ file:set_cwd("tmp"),
+ erl_tar:add(Tar, "bin", []),
+ erl_tar:add(Tar, "erts-" ++ ErtsVsn, []),
+ erl_tar:add(Tar, "releases", []),
+ erl_tar:add(Tar, "lib", []),
+ erl_tar:close(Tar),
+ file:set_cwd(Cwd),
+ io:fwrite("Removing directory \"tmp\" ...~n"),
+ remove_dir_tree("tmp"),
+ ok.
+
+
+install(RelFileName, RootDir) ->
+ TarFile = RelFileName ++ ".tar.gz",
+ io:fwrite("Extracting ~s ...~n", [TarFile]),
+ extract_tar(TarFile, RootDir),
+ StartErlDataFile = filename:join([RootDir, "releases", "start_erl.data"]),
+ {ok, StartErlData} = read_txt_file(StartErlDataFile),
+ [ErlVsn, RelVsn| _] = string:tokens(StartErlData, " \n"),
+ ErtsBinDir = filename:join([RootDir, "erts-" ++ ErlVsn, "bin"]),
+ BinDir = filename:join([RootDir, "bin"]),
+ io:fwrite("Substituting in erl.src, start.src and start_erl.src to\n"
+ "form erl, start and start_erl ...\n"),
+ subst_src_scripts(["erl", "start", "start_erl"], ErtsBinDir, BinDir,
+ [{"FINAL_ROOTDIR", RootDir}, {"EMU", "beam"}],
+ [preserve]),
+ io:fwrite("Creating the RELEASES file ...\n"),
+ create_RELEASES(RootDir,
+ filename:join([RootDir, "releases", RelFileName])).
+
+%% LOCALS
+
+%% make_script(RelFileName)
+%%
+make_script(RelFileName) ->
+ Opts = [no_module_tests],
+ systools:make_script(RelFileName, Opts).
+
+%% make_tar(RelFileName)
+%%
+make_tar(RelFileName) ->
+ RootDir = code:root_dir(),
+ systools:make_tar(RelFileName, [{erts, RootDir}]).
+
+%% extract_tar(TarFile, DestDir)
+%%
+extract_tar(TarFile, DestDir) ->
+ erl_tar:extract(TarFile, [{cwd, DestDir}, compressed]).
+
+create_RELEASES(DestDir, RelFileName) ->
+ release_handler:create_RELEASES(DestDir, RelFileName ++ ".rel").
+
+subst_src_scripts(Scripts, SrcDir, DestDir, Vars, Opts) ->
+ lists:foreach(fun(Script) ->
+ subst_src_script(Script, SrcDir, DestDir,
+ Vars, Opts)
+ end, Scripts).
+
+subst_src_script(Script, SrcDir, DestDir, Vars, Opts) ->
+ subst_file(filename:join([SrcDir, Script ++ ".src"]),
+ filename:join([DestDir, Script]),
+ Vars, Opts).
+
+subst_file(Src, Dest, Vars, Opts) ->
+ {ok, Conts} = read_txt_file(Src),
+ NConts = subst(Conts, Vars),
+ write_file(Dest, NConts),
+ case lists:member(preserve, Opts) of
+ true ->
+ {ok, FileInfo} = file:read_file_info(Src),
+ file:write_file_info(Dest, FileInfo);
+ false ->
+ ok
+ end.
+
+%% subst(Str, Vars)
+%% Vars = [{Var, Val}]
+%% Var = Val = string()
+%% Substitute all occurrences of %Var% for Val in Str, using the list
+%% of variables in Vars.
+%%
+subst(Str, Vars) ->
+ subst(Str, Vars, []).
+
+subst([$%, C| Rest], Vars, Result) when $A =< C, C =< $Z ->
+ subst_var([C| Rest], Vars, Result, []);
+subst([$%, C| Rest], Vars, Result) when $a =< C, C =< $z ->
+ subst_var([C| Rest], Vars, Result, []);
+subst([$%, C| Rest], Vars, Result) when C == $_ ->
+ subst_var([C| Rest], Vars, Result, []);
+subst([C| Rest], Vars, Result) ->
+ subst(Rest, Vars, [C| Result]);
+subst([], _Vars, Result) ->
+ lists:reverse(Result).
+
+subst_var([$%| Rest], Vars, Result, VarAcc) ->
+ Key = lists:reverse(VarAcc),
+ case lists:keysearch(Key, 1, Vars) of
+ {value, {Key, Value}} ->
+ subst(Rest, Vars, lists:reverse(Value, Result));
+ false ->
+ subst(Rest, Vars, [$%| VarAcc ++ [$%| Result]])
+ end;
+subst_var([C| Rest], Vars, Result, VarAcc) ->
+ subst_var(Rest, Vars, Result, [C| VarAcc]);
+subst_var([], Vars, Result, VarAcc) ->
+ subst([], Vars, [VarAcc ++ [$%| Result]]).
+
+copy_file(Src, Dest) ->
+ copy_file(Src, Dest, []).
+
+copy_file(Src, Dest, Opts) ->
+ {ok, InFd} = file:open(Src, [raw, binary, read]),
+ {ok, OutFd} = file:open(Dest, [raw, binary, write]),
+ do_copy_file(InFd, OutFd),
+ file:close(InFd),
+ file:close(OutFd),
+ case lists:member(preserve, Opts) of
+ true ->
+ {ok, FileInfo} = file:read_file_info(Src),
+ file:write_file_info(Dest, FileInfo);
+ false ->
+ ok
+ end.
+
+do_copy_file(InFd, OutFd) ->
+ case file:read(InFd, ?BUFSIZE) of
+ {ok, Bin} ->
+ file:write(OutFd, Bin),
+ do_copy_file(InFd, OutFd);
+ eof ->
+ ok
+ end.
+
+write_file(FName, Conts) ->
+ {ok, Fd} = file:open(FName, [write]),
+ file:write(Fd, Conts),
+ file:close(Fd).
+
+read_txt_file(File) ->
+ {ok, Bin} = file:read_file(File),
+ {ok, binary_to_list(Bin)}.
+
+remove_dir_tree(Dir) ->
+ remove_all_files(".", [Dir]).
+
+remove_all_files(Dir, Files) ->
+ lists:foreach(fun(File) ->
+ FilePath = filename:join([Dir, File]),
+ {ok, FileInfo} = file:read_file_info(FilePath),
+ case FileInfo#file_info.type of
+ directory ->
+ {ok, DirFiles} = file:list_dir(FilePath),
+ remove_all_files(FilePath, DirFiles),
+ file:del_dir(FilePath);
+ _ ->
+ file:delete(FilePath)
+ end
+ end, Files).
+ ]]></code>
+ </section>
+</chapter>