Installing mod_perl without superuser privileges

As you have seen from my previous articles, mod_perl enabled Apache consists of two main components: Perl modules and Apache itself. While installing Apache without root privileges is easy, one should know how to install Perl modules in a nonsystem-wide location. In this article, I'll demonstrate ways to complete this task.

In the examples, I'll use stas as a username, and /home/stas as the home directory for that user.

Installing Perl Modules Into a Directory of Choice

Since without superuser permissions you aren't allowed to install modules into system directories such as /usr/lib/perl5, you need to find out how to install the modules under your home directory. It's easy.

First, you have to decide where to install the modules. The simplest approach is to simulate the portion of the / file system relevant to Perl under your home directory. Actually we need only two directories:


  /home/stas/bin
  /home/stas/lib

We don't have to create them, since that will be done automatically when the first module is installed. Ninety-nine percent of the files will go into the lib directory. Occasionally, when some module distribution comes with Perl scripts, these will go into the bin directory. This directory will be created if it doesn't exist.

Let's install the CGI.pm package, which includes a few other CGI::* modules. As usual, download the package from the CPAN repository, unpack it and chdir to the newly created directory.

Now do a standard perl Makefile.PL to prepare a Makefile, but this time tell MakeMaker to use your Perl installation directories instead of the defaults.


  % perl Makefile.PL PREFIX=/home/stas

PREFIX=/home/stas is the only part of the installation process that is different from usual. Note that if you don't like how MakeMaker chooses the rest of the directories, or if you are using an older version that requires an explicit declaration of all the target directories, then do this:


  % perl Makefile.PL PREFIX=/home/stas \
    INSTALLPRIVLIB=/home/stas/lib/perl5 \
    INSTALLSCRIPT=/home/stas/bin \
    INSTALLSITELIB=/home/stas/lib/perl5/site_perl \
    INSTALLBIN=/home/stas/bin \
    INSTALLMAN1DIR=/home/stas/lib/perl5/man  \
    INSTALLMAN3DIR=/home/stas/lib/perl5/man3

The rest is as usual:


  % make
  % make test
  % make install

make install installs all the files in the private repository. Note that all the missing directories are created automatically, so there is no need to create them. Here (slightly edited) is what it does :


  Installing /home/stas/lib/perl5/CGI/Cookie.pm
  Installing /home/stas/lib/perl5/CGI.pm
  Installing /home/stas/lib/perl5/man3/CGI.3
  Installing /home/stas/lib/perl5/man3/CGI::Cookie.3
  Writing /home/stas/lib/perl5/auto/CGI/.packlist
  Appending installation info to /home/stas/lib/perl5/perllocal.pod

If you have to use the explicit target parameters, then instead of a single PREFIX parameter, you will find it useful to create a file called, for example, ~/.perl_dirs (where ~ is /home/stas in our example) containing:


    PREFIX=/home/stas \
    INSTALLPRIVLIB=/home/stas/lib/perl5 \
    INSTALLSCRIPT=/home/stas/bin \
    INSTALLSITELIB=/home/stas/lib/perl5/site_perl \
    INSTALLBIN=/home/stas/bin \
    INSTALLMAN1DIR=/home/stas/lib/perl5/man  \
    INSTALLMAN3DIR=/home/stas/lib/perl5/man3

From now on, any time you want to install Perl modules locally, you simply execute:


  % perl Makefile.PL `cat ~/.perl_dirs`
  % make
  % make test
  % make install

Using this method, you can easily maintain several Perl module repositories. For example, you could have one for production Perl and another for development:


  % perl Makefile.PL `cat ~/.perl_dirs.production`

or


  % perl Makefile.PL `cat ~/.perl_dirs.develop`

Making Your Scripts Find the Locally Installed Modules

Perl modules are generally placed in four main directories. To find these directories, execute:


  % perl -V

The output contains important information about your Perl installation. At the end you will see:


  Characteristics of this binary (from libperl):
  Built under linux
  Compiled at Apr  6 1999 23:34:07
  @INC:
    /usr/lib/perl5/5.00503/i386-linux
    /usr/lib/perl5/5.00503
    /usr/lib/perl5/site_perl/5.005/i386-linux
    /usr/lib/perl5/site_perl/5.005
    .

It shows us the content of the Perl special variable @INC, which is used by Perl to look for its modules. It is equivalent to the PATH environment variable in Unix shells that is used to find executable programs.

Notice that Perl looks for modules in the . directory too, which stands for the current directory. It's the last entry in the above output.

Of course, this example is from version 5.00503 of Perl installed on my x86 architecture PC running Linux. That's why you see i386-linux and 5.00503. If your system runs a different version of Perl, operating system, processor or chipset architecture, then some of the directories will have different names.

I also have a perl-5.6.1 installed under /usr/local/lib/ so when I do:


  % /usr/local/bin/perl5.6.1 -V

I see:


  @INC:
    /usr/local/lib/perl5/5.6.1/i586-linux
    /usr/local/lib/perl5/5.6.1
    /usr/local/lib/site_perl/5.6.1/i586-linux
    /usr/local/lib/site_perl

Previously in the Series

mod_perl in 30 minutes

Why mod_perl?

Note that it's still Linux, but the newer Perl version uses the version of my Pentium processor (thus the i586 and not i386). This makes use of compiler optimizations for Pentium processors when the binary Perl extensions are created.

All the platform specific files, such as compiled C files glued to Perl with XS or SWIG, are supposed to go into the i386-linux-like directories.

Important: As we have installed the Perl modules into nonstandard directories, we have to let Perl know where to look for the four directories. There are two ways to accomplish this: You can set the PERL5LIB environment variable or you can modify the @INC variable in your scripts.

Assuming that we use perl-5.00503, in our example the directories are:


    /home/sbekman/lib/perl5/5.00503/i386-linux
    /home/sbekman/lib/perl5/5.00503
    /home/sbekman/lib/perl5/site_perl/5.005/i386-linux
    /home/sbekman/lib/perl5/site_perl/5.005

As mentioned before, you find the exact directories by executing perl -V and replacing the global Perl installation's base directory with your home directory.

Modifying @INC is quite easy. The best approach is to use the lib module (pragma), by adding the following snippet at the top of any of your scripts that require the locally installed modules.


  use lib qw(/home/stas/lib/perl5/5.00503/
             /home/stas/lib/perl5/site_perl/5.005);

Another way is to write code to modify @INC explicitly:


  BEGIN {
    unshift @INC,
      qw(/home/stas/lib/perl5/5.00503
         /home/stas/lib/perl5/5.00503/i386-linux
         /home/stas/lib/perl5/site_perl/5.005
         /home/stas/lib/perl5/site_perl/5.005/i386-linux);
        }

Note that with the lib module we don't have to list the corresponding architecture specific directories, since it adds them automatically if they exist (to be exact, when $dir/$archname/auto exists).

Also, notice that both approaches prepend the directories to be searched to @INC. This allows you to install a more recent module into your local repository and Perl will use it instead of the older one installed in the main system repository.

Both approaches modify the value of @INC at compilation time. The lib module uses the BEGIN block as well, but internally.

Now, let's assume the following scenario. I have installed the LWP package in my local repository. Now I want to install another module (e.g. mod_perl) that has LWP listed in its prerequisites list. I know that I have LWP installed, but when I run perl Makefile.PL for the module I'm about to install I'm told that I don't have LWP installed.

There is no way for Perl to know that we have some locally installed modules. All it does is search the directories listed in @INC, and since the latter contains only the default four directories (plus the . directory), it cannot find the locally installed LWP package. We cannot solve this problem by adding code to modify @INC, but changing the PERL5LIB environment variable will do the trick. If you are using t?csh for interactive work, then do this:


  setenv PERL5LIB /home/stas/lib/perl5/5.00503:
  /home/stas/lib/perl5/site_perl/5.005

It should be a single line with directories separated by colons (:) and no spaces. If you are a (ba)?sh user, then do this:


  export PERL5LIB=/home/stas/lib/perl5/5.00503:
  /home/stas/lib/perl5/site_perl/5.005

Again, make it a single line. If you use bash, then you can use multi-line commands by terminating split lines with a backslash (\), like this:


  export PERL5LIB=/home/stas/lib/perl5/5.00503:\
  /home/stas/lib/perl5/site_perl/5.005

As with use lib, Perl automatically prepends the architecture specific directories to @INC if those exist.

When you have done this, verify the value of the newly configured @INC by executing perl -V as before. You should see the modified value of @INC:


  % perl -V

  Characteristics of this binary (from libperl): 
  Built under linux
  Compiled at Apr  6 1999 23:34:07
  %ENV:
    PERL5LIB="/home/stas/lib/perl5/5.00503:
    /home/stas/lib/perl5/site_perl/5.005"
  @INC:
    /home/stas/lib/perl5/5.00503/i386-linux
    /home/stas/lib/perl5/5.00503
    /home/stas/lib/perl5/site_perl/5.005/i386-linux
    /home/stas/lib/perl5/site_perl/5.005
    /usr/lib/perl5/5.00503/i386-linux
    /usr/lib/perl5/5.00503
    /usr/lib/perl5/site_perl/5.005/i386-linux
    /usr/lib/perl5/site_perl/5.005
    .

When everything works as you want it to, add these commands to your .tcshrc or .bashrc file. The next time you start a shell, the environment will be ready for you to work with the new Perl.

Note that if you have a PERL5LIB setting, then you don't need to alter the @INC value in your scripts. But if, for example, someone else (who doesn't have this setting in the shell) tries to execute your scripts, then Perl will fail to find your locally installed modules. The best example is a crontab script that might use a different SHELL environment and, therefore, the PERL5LIB setting won't be available to it.

So the best approach is to have both the PERL5LIB environment variable and the explicit @INC extension code at the beginning of the scripts as described above.

The CPAN.pm Shell and Locally Installed Modules

The CPAN.pm shell saves a great deal of time when dealing with the installation of Perl modules and keeping them up to date. It does the job for us, even detecting the missing modules listed in prerequisites, fetching and installing them. So you may wonder whether you can use CPAN.pm to maintain your local repository as well.

When you start the CPAN interactive shell, it searches first for the user's private configuration file and then for the system-wide one. When I'm logged as user stas, the two files on my setup are:


    /home/stas/.cpan/CPAN/MyConfig.pm
    /usr/lib/perl5/5.00503/CPAN/Config.pm

If there is no CPAN shell configured on your system, then when you start the shell for the first time it will ask you a dozen configuration questions and then create the Config.pm file for you.

If you already have it system-wide configured, then you should have a /usr/lib/perl5/5.00503/CPAN/Config.pm. If you have a different Perl version, then alter the path to use your Perl's version number when looking up the file. Create the directory (mkdir -p creates the whole path at once) where the local configuration file will go:


  % mkdir -p /home/stas/.cpan/CPAN

Now copy the system wide configuration file to your local one.


  % cp /usr/lib/perl5/5.00503/CPAN/Config.pm \
  /home/stas/.cpan/CPAN/MyConfig.pm

The only thing left is to change the base directory of .cpan in your local file to the one under your home directory. On my machine, I replace /usr/src/.cpan (that's where my system's .cpan directory resides) with /home/stas. I use Perl, of course!


  % perl -pi -e 's|/usr/src|/home/stas|' \
  /home/stas/.cpan/CPAN/MyConfig.pm

Now you have the local configuration file ready, you have to tell it what special parameters you need to pass when executing the perl Makefile.PL stage.

Open the file in your favorite editor and replace line:


  'makepl_arg' => q[],

with:


  'makepl_arg' => q[PREFIX=/home/stas],

Now you've finished the configuration. Assuming that you are logged in as the same user you have prepared the local installation for (stas in our example), start it like this:


  % perl -MCPAN -e shell

From now on, any module you try to install will be installed locally. If you need to install some system modules, then just become the superuser and install them in the same way. When you are logged in as the superuser, the system-wide configuration file will be used instead of your local one.

If you have used more than just the PREFIX variable, then modify MyConfig.pm to use them. For example, if you have used these variables:


    perl Makefile.PL PREFIX=/home/stas \
    INSTALLPRIVLIB=/home/stas/lib/perl5 \
    INSTALLSCRIPT=/home/stas/bin \
    INSTALLSITELIB=/home/stas/lib/perl5/site_perl \
    INSTALLBIN=/home/stas/bin \
    INSTALLMAN1DIR=/home/stas/lib/perl5/man  \
    INSTALLMAN3DIR=/home/stas/lib/perl5/man3

then replace PREFIX=/home/stas in the line:


  'makepl_arg' => q[PREFIX=/home/stas],

with all the variables from above, so that the line becomes:


  'makepl_arg' => q[PREFIX=/home/stas \
    INSTALLPRIVLIB=/home/stas/lib/perl5 \
    INSTALLSCRIPT=/home/stas/bin \
    INSTALLSITELIB=/home/stas/lib/perl5/site_perl \
    INSTALLBIN=/home/stas/bin \
    INSTALLMAN1DIR=/home/stas/lib/perl5/man  \
    INSTALLMAN3DIR=/home/stas/lib/perl5/man3],

If you arrange all the above parameters in one line, then you can remove the backslashes (\).

Making a Local Apache Installation

Just like with Perl modules, if you don't have permissions to install files into the system area, then you have to install them locally under your home directory. It's almost the same as a plain installation, but you have to run the server listening to a port number greater than 1024, since only root processes can listen to lower-numbered ports.

Another important issue you have to resolve is how to add startup and shutdown scripts to the directories used by the rest of the system services. You will have to ask your system administrator to assist you with this issue.

To install Apache locally, all you have to do is to tell .configure in the Apache source directory what target directories to use. If you are following the convention that I use, which makes your home directory look like the / (base) directory, then the invocation parameters would be:


  ./configure --prefix=/home/stas

Apache will use the prefix for the rest of its target directories instead of the default /usr/local/apache. If you want to see what they are, then before you proceed add the --show-layout option:


  ./configure --prefix=/home/stas --show-layout

You might want to put all the Apache files under /home/stas/apache following Apache's convention:


  ./configure --prefix=/home/stas/apache

If you want to modify some or all of the names of the automatically created directories:


  ./configure --prefix=/home/stas/apache \
    --sbindir=/home/stas/apache/sbin
    --sysconfdir=/home/stas/apache/etc
    --localstatedir=/home/stas/apache/var \
    --runtimedir=/home/stas/apache/var/run \
    --logfiledir=/home/stas/apache/var/logs \
    --proxycachedir=/home/stas/apache/var/proxy

That's all!

Also remember that you can start the script only under a user and group you belong to. You must set the User and Group directives in httpd.conf to appropriate values.

Manual Local mod_perl Enabled Apache Installation

Now that we have learned how to install local Apache and Perl modules separately, let's see how to install mod_perl enabled Apache in our home directory. It's almost as simple as doing each one separately, but there is one wrinkle you need to know about that I'll mention at the end of this section.

Let's say you have unpacked the Apache and mod_perl sources under /home/stas/src and they look like this:


  % ls /home/stas/src
  /home/stas/src/apache_x.x.x
  /home/stas/src/mod_perl-x.xx

where x.xx are the version numbers as usual. You want the Perl modules from the mod_perl package to be installed under /home/stas/lib/perl5 and the Apache files to go under /home/stas/apache. The following commands will do that for you:


  % perl Makefile.PL \
  PREFIX=/home/stas \
  APACHE_PREFIX=/home/stas/apache \
  APACHE_SRC=../apache_x.x.x/src \
  DO_HTTPD=1 \
  USE_APACI=1 \
  EVERYTHING=1
  % make && make test && make install 
  % cd ../apache_x.x.x
  % make install

If you need some parameters to be passed to the .configure script, as we saw in the previous section, then use APACI_ARGS. For example:


  APACI_ARGS='--sbindir=/home/stas/apache/sbin, \
    --sysconfdir=/home/stas/apache/etc, \
    --localstatedir=/home/stas/apache/var, \
    --runtimedir=/home/stas/apache/var/run, \
    --logfiledir=/home/stas/apache/var/logs, \
    --proxycachedir=/home/stas/apache/var/proxy'

Note that the above multi-line splitting will work only with bash, tcsh users will have to list all the parameters on a single line.

Basically the installation is complete. The only remaining problem is the @INC variable. This won't be correctly set if you rely on the PERL5LIB environment variable unless you set it explicitly in a startup file that is require'd before loading any other module that resides in your local repository. A much nicer approach is to use the lib pragma as we saw before, but in a slightly different way -- we use it in the startup file and it affects all the code that will be executed under mod_perl handlers. For example:


  PerlRequire /home/stas/apache/perl/startup.pl

where startup.pl starts with:


  use lib qw(/home/stas/lib/perl5/5.00503/
             /home/stas/lib/perl5/site_perl/5.005);

Note that you can still use the hard-coded @INC modifications in the scripts themselves, but be aware that scripts modify @INC in BEGIN blocks and mod_perl executes the BEGIN blocks only when it performs script compilation. As a result, @INC will be reset to its original value after the scripts are compiled and the hard-coded settings will be forgotten.

The only place you can alter the ``original'' value is during the server configuration stage either in the startup file or by putting


  PerlSetEnv Perl5LIB \
  /home/stas/lib/perl5/5.00503/:/home/stas/lib/perl5/site_perl/5.005

in httpd.conf, but the latter setting will be ignored if you use the PerlTaintcheck setting, and I hope you do use it.

The remainder of the mod_perl configuration and use is just the same as if you were installing mod_perl as a superuser.

Local mod_perl Enabled Apache Installation with CPAN.pm

Assuming that you have configured CPAN.pm to install Perl modules locally as explained earlier in this article, the installation is simple. Start the CPAN.pm shell, set the arguments to be passed to perl Makefile.PL (modify the example setting to suit your needs), and tell <CPAN.pm> to do the rest for you:


  % perl -MCPAN -eshell
  cpan> o conf makepl_arg 'DO_HTTPD=1 USE_APACI=1 EVERYTHING=1 \
        PREFIX=/home/stas APACHE_PREFIX=/home/stas/apache'
  cpan> install mod_perl

When you use CPAN.pm for local installations, after the mod_perl installation is complete, you must make sure that the value of makepl_arg is restored to its original value.

The simplest way to do this is to quit the interactive shell by typing quit and re-entering it. But if you insist, then here is how to make it work without quitting the shell. You really want to skip this :)

If you want to continue working with CPAN *without* quitting the shell, then you must:

Previously in the Series

mod_perl in 30 minutes

Why mod_perl?

  1. remember the value of makepl_arg
  2. change it to suit your new installation
  3. build and install mod_perl
  4. restore it after completing mod_perl installation

this is quite a cumbersome task as of this writing, but I believe that CPAN.pm will eventually be improved to handle this more easily.

So if you are still with me, then start the shell as usual:


  % perl -MCPAN -eshell

First, read the value of the makepl_arg:


  cpan> o conf makepl_arg

  PREFIX=/home/stas

It will be something like PREFIX=/home/stas if you configured CPAN.pm to install modules locally. Save this value:


  cpan> o conf makepl_arg.save PREFIX=/home/stas

Second, set a new value, to be used by the mod_perl installation process. (You can add parameters to this line, or remove them, according to your needs.)


  cpan> o conf makepl_arg 'DO_HTTPD=1 USE_APACI=1 EVERYTHING=1 \
        PREFIX=/home/stas APACHE_PREFIX=/home/stas/apache'

Third, let <CPAN.pm> build and install mod_perl for you:


  cpan> install mod_perl

Fourth, reset the original value to makepl_arg. We do this by printing the value of the saved variable and assigning it to makepl_arg.


  cpan> o conf makepl_arg.save

  PREFIX=/home/stas

  cpan> o conf makepl_arg PREFIX=/home/stas

Not so neat, but a working solution. You could have written the value on a piece of paper instead of saving it to makepl_arg.save, but you are more likely to make a mistake that way.

References

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