Installing mod_perl without superuser privileges

by Stas Bekman
April 10, 2002

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.

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