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Managing Perl Installations: A SysAdmin’s View 1,2,3

Baden HughesDepartment of Computer Science and Software Engineering

The University of Melbournebadenh@csse.unimelb.edu.au

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What the title really means …

� Managing Perl Installations: A SysAdmin’s View 1�Useful things a SysAdmin should know about Perl

� Managing Perl Installations: A SysAdmin’s View 2

�What you can do if you actually RTFM

� Managing Perl Installations: A SysAdmin’s View 3�5327 other things you can do with CPAN

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Overview

�Perl, Modules, CPAN�Problems and Objectives�The Sharp and Pointy Bits

�Module Management�Bundles�Working within User-space

�Conclusion

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Perl

� http://www.perl.org� Perl is a dynamic procedural programming

language � Designed by Larry Wall, maintained as open

source project� First released in 1987� Perl borrows features from C, shell scripting

(sh), awk, sed, Lisp, and (to a lesser extent) many other programming languages.

� Ubiquitous

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Perl Modules

� A Perl module is a discrete component of software for the Perl programming language.

� Modules distinguished by a unique namespace, e.g. "CGI" or "Net::FTP" or "XML::Parser".

� Convention of one module per file with a *.pm extension.

� Collection of one or more modules, with accompanying documentation (yes, really) and build scripts, compose a package.

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CPAN

�Comprehensive Perl Archive Network�http://cpan.org�A large collection of Perl software (modules,

packages and scripts) and associated documentation

�A Perl module (CPAN.pm)perl –MCPAN –e shell

�Used to download and install Perl software from the CPAN archive

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Scoping the Problem

� On multi-user systems, particularly where there are Perl-oriented developers of some flavour, being responsible for Perl can be quite onerous

� The defaults for maintaining Perl on a shared system are typically�Every user compiles and runs their own version of Perl�Constant trickle of requests for Perl and/or module

upgrades and/or additions� Naturally neither of these are considered

desirable by typical sysadmins since they have both system resource and human effort constraints

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Objectives

� Get smarter: Perl itself can make managing a Perl installation on a shared system much easier

� Objectives�Demonstrate ways to manage Perl installations based

on commonly occurring tasks�Show ‘core Perl’ methods that work everywhere, not

distribution specific methods which only work on one platform

� Get users to help you, rather than the other way around �

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Modules

�Which modules are on my system ?� Installing modules�Removing modules

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Q: Which modules are on my system ? A: perldoc perllocal

�perldoc perllocal will identify a list of modules, their version, location etc.

Tue Oct 4 17:00:07 2005: "Module" Geo::GNIS

* "installed into: /usr/lib/perl5/site_perl/5.8.5"

* "LINKTYPE: dynamic"

* "VERSION: 0.01"

* "EXE_FILES: "

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Q: Which modules are on my system ? A: ExtUtils::Installed

� Use the ExtUtils::Installed module

#!/usr/local/bin/perluse ExtUtils::Installed; my $instmod = ExtUtils::Installed->new(); foreach my $module ($instmod->modules()) {

my $version = $instmod->version($module) || "???";print "$module -- $version\n";

}

produces a list of modules and their version(s)� ExtUtils::Installed is in the standard Perl installation, and uses the

installation generated files for modules to determine status

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Q: Which modules are on my system ? A: pmtools

� The pmtools suite to help navigate and manage Perl module installations

� Obtain them at http://language.perl.com/misc/pmtools-1.00.tar.gz.

� pmtools -- a suite of small programs to help manage modules�pmpath - show the module's full path �pmvers - get a module version number �pmdesc - get a module description �pmall - get all installed modules pmdesc descriptions �pminst - find what's installed

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Installing Modules

�With CPAN.pm, installing a new module is trivial:perl -MCPAN -e 'install Esoteric::Module’

�Finding which modules exist and their versions can also be done directly via CPANcpan > i $KEYWORD

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Removing Modules (1)

� By using the ExtUtils::Installed and ExtUtils::Packlistmodules that come with Perl#!/usr/local/bin/perl -w use ExtUtils::Packlist; use ExtUtils::Installed; $ARGV[0] or die "Usage: $0 Module::Name\n"; my $mod = $ARGV[0]; my $inst = ExtUtils::Installed->new(); foreach my $item (sort($inst->files($mod))) { print "removing $item\n"; unlink $item; } my $packfile = $inst->packlist($mod)->packlist_file(); print "removing $packfile\n";

unlink $packfile;

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Removing Modules (2)

�PPM can uninstall modulesshell>ppm remove $MODULE-NAME

�CPAN.pm doesn’t have a ‘remove’ option

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Bundles

�What is a Bundle ?�Which Bundles exist ?�Making Bundles (single point of Perl

administration for multiple systems)

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Q: What is a Bundle ?

� A bundle is "A group of related modules on CPAN (or some repository“� A bundle can be any collection of modules, related or not.

� Bundles are used by CPAN.pm to install a group of modules quickly and easily.

� A bundle is essentially a module in the Bundle:: namespace that has all the look and feel of a module but really isn't since it contains no code instead having a manifest of modules to be installed.

� There are a number of existing module bundles that you can view as examples to help in building your own.

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Q: Which Bundles already exist ?

� You can get a list of bundle distributions on search.cpan.org and CPAN.pm also lists all currently available bundles when you type 'b' at the prompt.

cpan> b Bundle Bundle::ABH (A/AB/ABH/Bundle-ABH-1.04.tar.gz) Bundle Bundle::AO::Base (I/IX/IX/AO-0.32.tar.gz) Bundle Bundle::AO::Standard (I/IX/IX/AO-0.32.tar.gz) Bundle Bundle::Apache (D/DO/DOUGM/mod_perl-1.25.tar.gz) Bundle Bundle::Apache::ASP (C/CH/CHAMAS/Apache-ASP-2.09.tar.gz) Bundle

� If you give 'b' a module argument it will list extended information about the bundle itself.

cpan> b Bundle::DBIBundle id = Bundle::DBICPAN_USERID TIMB (Tim Bunce <Tim.Bunce@pobox.com>) CPAN_VERSION 1.03 CPAN_FILE T/TI/TIMB/DBI-1.15.tar.gz MANPAGE Bundle::DBI - A bundle to install DBI and required

modules. CONTAINS Storable Net::Daemon RPC::PlServer Getopt::Long DBIINST_FILE /usr/local/lib/perl5/site_perl/5.005/sun4-

solaris/Bundle/DBI.pm INST_VERSION 1.03

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Q: How can I make a Bundle ?

� Use the autobundle feature of CPAN.pm� autobundle will, if no arguments are given, inventory

all modules installed on the system and make a systemwide bundle.

� If you only want a few modules in the bundle you can simply give it a list of modules and it will do the rest.user@host /home/user/> perl -MCPAN -eshell cpan> autobundle CGI Crypt::Rot13 Date::ChristmasDate::Manip

� By default bundles are named "Snapshot_YYYY_MM_DD_HH_MM_SS.pm"

� The resultant file may then be used with the CPAN.pmperl -MCPAN -e 'install Bundle::Snapshot_2006_04_09_10_36_24.pm'

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Bundles and System Administration

�Bundles are a very convenient way to maintain homogeneous installations across multiple systems, including across architectures�Personal experience: create bundles for local

and external modules; store bundles in a repository; checkout and install sequentially on development, test and production servers; single install experience, guaranteed homogeneity

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User-space Perl

�Alternative locations for Modules�Standard Perl plus Custom Modules�User-specific CPAN

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Working with Perl in User Space

�Advanced users often want more control over their Perl installation on shared systems

�SysAdmins are reluctant to let users “do as they see fit” to system wide utilities

�CPAN requires elevated privileges�Fortunately Perl offers several ways

around this problem

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Installing Perl Modules in Alternative Locations� Any manually installed Perl module can be trivially

installed in an alternative location, eg within ~/� Set PREFIX and LIB when you run the Makefile.PL to

install� LIB is where the module files will go� PREFIX is the stub directory for everything elseuser@host$ perl Makefile.PL \\LIB=/home/user/lib \\PREFIX=/home/user/lib

� The reason this works is because Perl has a standard way of installing modules, called MakeMaker

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Standard Perl + Custom Modules

� Sometimes however, a user simply wants to install a few modules but use the standard system wide Perl installation

� In this case, setting the PERL5LIB environment variable can allow the inclusion of modules installed in non-standard locations

PERL5LIB=${PERL5LIB:+$PERL5LIB:}$HOME/lib/perl5

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User-space CPAN

� CPAN can be configured differently for each user, and can install modules to custom locations on a system, eg ~/lib/perl5 and ~/share/man

� MyConfig.pm is a base module for precisely this purpose, and can be used in place of a standard CPAN.pm

� Allows users to directly use CPAN functionality, with no run time environment variables required

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Conclusion

�Perl is ubiquitous�On shared systems, Perl has native tools

to reduce the administrative overhead�Users can be empowered to maintain their

own Perl infrastructure without significant effort

�RTFM’ing can actually be beneficial �