Re: to conffile or not to conffile

[Matt Armstrong <matt@lickey.com>]

Julian Gilbey <J.D.Gilbey@qmw.ac.uk> writes:

> On Tue, Oct 16, 2001 at 10:46:52PM -0600, Matt Armstrong wrote:
>
> Who needs to edit it, the sysadmin or the maintainer scripts?
> 
>>     - I really do want to make it a conffile, so the user is notified of
>>       future options.
> 
> There are other ways to do this -- see below.
> 
>>     - I really do want to ask the user what serial port to use when the
>>       thing is installed.
> 
> Use debconf to get this info.
> 
> Appropriate solution: The first time this package is installed, use
> debconf to get the info, then write a config file to /etc.  Maybe add
> a couple of comment lines:
> 
> # Please do not modify the next line
> # config_version=0.3
> 
> On upgrades, check the "config_version" line, and if you are now
> introducing a later version, either use debconf to get the desired
> newer config settings or just append the default values to the
> existing config file with appropriate comments, taking care to update
> the config_version line and not to affect any of the sysadmin's
> settings.
> 
> Remember that if every package told the sysadmin of all the new bells
> and whistles, upgrades would be dreadful; you need only ask them for
> new information really needed via debconf.

Yes I agree with you and Joey that this is probably the best way to
go.  In complex packages I think this is hard to get right -- it
seemed like postfix's maintainer scripts screwed me over every time I
upgraded until he added a "don't touch my configuration" option which
I now select every time.  So I think if done wrong this approach can
breed user mistrust.

Anyway, I've got two questions:

1) Does Debian have any useful packaging utilities used for simple
   programmatic editing of text files?  I'm not thinking sed/awk/perl
   here, but rather something along the lines of cfengine's
   "editfiles" capabilities.  It'd be cool to be able to do something
   like this (in some made up pseudo language).

    config = configfile("/etc/flipit.conf")
    if (!config)
        dump_default_config(config)
    else
        if (config.version() < 0.4)
            config.append_text(<<EOF)

# The default value for the new 'frob' option is 12
# but it can range from 0 to 100
# frob = 12
EOF
        config.set_version(0.4)
        end
    end

   Something like this implemented in Perl, Python, or Ruby might be a
   useful maintainer tool.  The starting point could be cfengine's
   "editfiles" functionality, but additional stuff could be added
   (such as a set/set version capability that maintains the "#
   config_version=XX" lines.

2) Is there anything wrong with a package's postinst script requiring
   Ruby?  If not, how would I express the dependency?  Were I to
   implement the above idea I'd want to do it in that language --
   doing OO stuff in Perl makes me want to cry.

-- 
matt