Saturday, March 15, 2008

OpenSolaris Wish List: Feature-based meta packages

The problem

There are many occasions when an administrator needs to install a particular feature on a system but tracking down the packages, patches, or revisions thereof is next to impossible. Consider the following scenarios:

  • A sysadmin is trying to build minimized systems that have a firewall, bash, python, and can support zones using Jumpstart. What needs to appear in the Jumpstart profile?
  • That same sysadmin then decides that a particular installed system needs to be augmented to support the OSPF routing protocol.
  • Some time passes and an updated feature of is released. The sysadmin needs to be able to update systems to support that feature without guessing which packages or patches are required. Note that the a subset of the required packages may not have been installed initially because they did not exist initially or they weren't required for to meet the dependencies of the earlier feature set.
  • A sysadmin notices a nifty feature mentioned in the "What's New" documentation and wants to determine if a recently patched system system supports the feature.
Dealing with any of these situations is very difficult today.

Most commonly, the best advice that is offered when trying to indicate what is required to have a particular feature is to say that the feature is available in Solaris X update Y. While that is true to a certain extent, that is not the complete story. It assumes that the system in question is in no way minimized and ignores the fact that the same patches that are integrated in update Y are also available for installation on releases before update Y.

Ongoing Work

The Image Packaging System looks to be outstanding work in this direction. The one-pager is likely the best place to look for a quick overview. While this will provide a good foundation, there are numerous posts to mailing lists of the form "I'm trying to install X, but pkg can't find it."

Suggested Approach

Some geeks (power users, whatever you would like to call them) will know the exact name of the packages that they want or will otherwise be able to search for them rather adeptly. Having the ability to say "I want bash" rather than "I want the same shell used by most Linux distros" is important.

I suspect that most people will be quite happy looking at their requirements and matching them up to advertised features. I suggest that the feature/* package namespace be reserved for meta-packages that represent features. A feature meta-package should not deliver any files, rather it just defines dependencies for the minimal set of packages required to support the feature. See the Package FMRIs and Versions section of pkg(5) for details on package naming.

For instance, if I needed the zones feature I should be able to say something along the lines of "pkg install feature/zones". This would likely correspond to an FMRI of pkg://,5.11-7:20080326T164523Z. When new features are updated, the build number (7 in the example FMRI) should be updated.

While searching the published packages would yield a pretty good list of packages required for supporting zones, someone needing the OSPF routing protocol may have a harder time with a search. However, installing feature/network/routing/ospf would likely know that the zebra or quagga package is needed (varying by Solaris release).

Integration with Documentation

With such an approach, the Solaris What's New documentation could be very helpful to sysadmins needing to update existing systems, installation profiles, etc. Consider the following, based upon a particular entry from the Solaris 10 What's New documentation.

IPsec Tunnel Reform

Solaris now implements IPsec Tunnel Mode per RFC 2401. Inner-packet selectors can be specified on a per-tunnel-interface basis using the new "tunnel" keyword of ipsecconf(1M). IKE and PF_KEY handle Tunnel Mode identities for Phase 2/Quick Mode. Interoperability with other IPsec implementations is greatly increased.

For more information, see Transport and Tunnel Modes in IPsec in System Administration Guide: IP Services. This feature is available via the feature/network/protocol/rfc2401software collection.

To help someone with this feature find documentation of this type in the future, a documentation system (installed on system or internet accessible) should be able to point a person interested in documentation related to a feature to the appropriate man page(s), online books, and other documentation.

Similarly, if the feature is just an update of an existing feature, having the documentation refer to a particular build (release, whatever works) of the feature package would be must useful.

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