Previously

Intro

As a sysadmin (”Ops”), I’ve had root responsibilities on NetBSD, FreeBSD, OpenBSD, Mac OS X, Solaris, and weirder systems like IRIX, AIX, and Linux. As a developer (”Dev”), I’ve used a bunch of those, sometimes without root privileges. Across all these contexts, to do my job reliably and productively, I found it often helped to use a cross-platform Unix package manager.

In the course of a couple decades of running mail servers, for pay and for myself, I’ve made a “DevOps” habit of observing and automating. This post is about how I recently synthesized old skills with new ones to make a big improvement in my mail-hosting automation.

Are any of your contexts like mine? Read on. You may conclude that my approach and/or tools could help you in your work. If so, maybe you can come to my hands-on workshop in a few weeks. If not, maybe we can work together another way.

Background

I’ve been running NetBSD for 20 years: from 1.1 in high school to 7.1, released two weeks ago. NetBSD’s continued growth and relevance is one of the reasons I keep choosing to run it.

I’ve been running qmail for almost as long: from 1.03 in my first job to 1.03 (plus a few third-party patches) today. qmail’s lack of continued growth and relevance makes it harder for me to keep choosing to run it. Yet I still do.

A friend wondered, in response to a recent post about refactoring my mail-server configuration, why I continue to make this choice when Postfix is ubiquitous and easy to work with. My friend made a good point. Postfix is the default MTA shipped with many operating systems — including NetBSD — and on the few occasions I’ve needed to tweak Postfix from its default behavior, it’s been easy enough. If it’d existed when my first employer and I needed an alternative to Sendmail, I’m sure I’d be happily running Postfix today.

But qmail 1.03 did exist by 1998. And by force of its compellingly different and better architecture, I found it both necessary and possible to understand SMTP, the nuances of running a production mail server on the open Internet, and the details that go into safely and reliably delivering a single message. qmail’s author, Dan Bernstein, also invented a new Maildir storage format whose desirable runtime behaviors delivered me a message about the significance of finding the right data structure — one of the few lessons I managed to learn in college-the-first-time. (A few years later, Bernstein’s djbdns would teach me very similar lessons about DNS.)

Anywho, I responded to my friend with the offhand rationale that my choice to continue with qmail stems from

A mélange of

As my weekly server update has grown more streamlined, the sharp edges of the qmail package have grown more salient. And a couple weeks ago, they scratched a friend trying to install it on a fresh NetBSD instance. So I wanted to take another stab at making things easier for my friend (and future-me, who I hope to be friends with).

It went well. Now that I’ve composed NetBSD and qmail into their finest two-part harmony yet, I’d like to tell you a tale of software archaeology, a tale replete with flexibility, persuasion, persistence, and very occasional free time. And possibly just a smidge of Sunk Cost Fallacy.

It’s not my shortest story. (Did I mention Sunk Cost Fallacy?) But if the problems I’ve tried to solve sound like problems you’re trying to solve, there’s likely something in it for you.

1997: Build from source

What’s wrong with installing software from source code by manually following its instructions? When you’re trying to learn how it works, not much at all. If you do this with qmail, you’ll learn how it

  • Makes use of several Unix users and groups for security partitioning,
  • Requires that those users and groups be created before it’ll compile,
  • Installs its programs and documentation to locations that need additional configuration to be useful to users, and
  • Expects its daemons to be managed in a way that almost certainly departs significantly from your OS’s usual (such as NetBSD’s rc.d subsystem).

When you’re trying to learn how qmail works, these are all important things to know. When you’re trying to integrate it into your systems, your habits, and your automations, these are important things to be able to forget.

There’s an abstraction layer for hiding such details: a package manager. NetBSD’s is spelled “pkgsrc” and pronounced “package source”.

2002: Maybe build from pkgsrc

After submitting a series of patch requests to pkgsrc, it was just about exactly 15 years ago that I was invited to commit directly to the repository. As a project, pkgsrc was mainly focused on automating dependencies, builds, installs, and uninstalls of third-party code from source code. As a developer and user, so was I.

We had a package of qmail. It was pretty rough. It jumped through hoops to create those users and groups early enough in the build, it didn’t place qmail’s programs or documentation in users’ existing paths, it didn’t offer NetBSD-style rc.d scripts, and if memory serves, uninstalling it didn’t really uninstall anything. And while pkgsrc could be used to generate binary packages, the qmail package very sensibly refused to.

My first commit to qmail (original) was from a future developer’s patch request. He provided an rc.d script that started and stopped qmail-send. Pretty cool.

2004: Definitely build from pkgsrc

Someday I hoped to produce a binary package that worked well. If I could start making our source package work well, I might get there someday.

One of DJB’s conditions for redistributions of qmail was that all files must be addressable in their documented default locations under the /var/qmail hierarchy. One of pkgsrc’s conditions for uninstalling files was that they must be stored under the /usr/pkg hierarchy. And, of course, if the programs and manual pages were installed into /usr/pkg, they’d be instantly available to users. Inspired by an idea from Matthew R. Green on the qmail discussion list, I taught the package to create symlinks under /var/qmail before running qmail’s installer, which then followed the symlinks. For example, a symlink in /var/qmail/bin pointing to /usr/pkg/bin induced qmail programs to install into /usr/pkg/bin as pkgsrc users would expect, while also being accessible via /var/qmail/bin as qmail users would expect.

Score! The symlink-before-install trick provided the basis for many contemporaneous improvements (original) and also obviated the need for path-related hacks (original) in a handful of packages depending on qmail. After a lot of careful work, our package suddenly provided a rather high-functioning qmail installation.

It even followed a whole bunch of the recommendations codified by the qmail community elders in the Life with qmail configuration guide. There was one big recommendation, by virtue of its mere existence, that it could not follow: the qmail elders strongly recommended avoiding packages entirely, for reasons like those in the “1997: Build from source” section above. Nonetheless, I asked for their review and feedback, received it, and applied it. The gist: I removed my NetBSD-specific customizations from the qmail package (original) and re-added them as a new qmail-run package (original), along with other tweaks intended to help users distinguish standard stuff that the community could support from custom stuff they should ask me about directly. (I wrote about the experience as a college-the-second-time application essay. Wound up going somewhere else.)

At this point, as I explained at a couple pkgsrcCons, for most “djbware” in pkgsrc, we could generate useful binary packages, but weren’t confident that we could meet DJB’s conditions for distributors.

For qmail in particular, binary packages were less useful. A qmail binary package built on one machine could run on another if and only if the numeric IDs of qmail’s users and groups were the same on both systems, which is not only mathematically exceedingly unlikely to happen at random, but often difficult to arrange for in the wild. FreeBSD Ports, among others, worked around this by permanently allocating a non-configurable set of IDs. Their decision could never have made sense for pkgsrc, where besides NetBSD we run on all manner of operating systems we don’t control. To fix it, we’d really have to fix it. But applying patches that changed visible behavior of the installed software was clearly against the redistribution conditions.

In late 2007, DJB placed qmail in the public domain. It became possible to apply the usual consideration for the costs and benefits of patching our package.

I was busy with college-the-second-time, particularly so with validating my goal to be a composer. For my own needs, I continued using source packages.

2011: Maybe install from a custom binary package

Motivated by the desire to improve the quality of our binary packages, pkgsrc grew an idea of DESTDIR. Source packages that knew about DESTDIR no longer installed directly onto the running system, but rather into a temporary staging directory from which a binary package was generated and then installed. (This was not a new idea; OpenBSD Ports, among others, beat us to it.) Once all our packages had been adapted, we could remove the old way. Then even source-centric developers like myself would notice when our binary packages weren’t working right.

I liked the sound of that and didn’t want to hold up progress, so I made what I thought were the smallest possible changes to minimally support DESTDIR (original).

Turns out, when the DESTDIR rapture finally came (original) in late 2015, I had not arranged for the qmail binary package to initialize its message queue.

The regression in our binary package occurred because my brain continued to assume it was not worth anyone’s time to try to use it, even though the meaning of the coming rapture was specifically that one day all package installs would be binary package installs.

The missing queue went unnoticed because on the mail server where I would’ve quickly noticed it, it hadn’t been missing! It was still there from before the DESTDIR rapture, when I’d first installed from the old-style source package.

(It also went unnoticed because very few people run qmail from pkgsrc. Even when lots of people ran qmail, pkgsrc’s package wasn’t great, pkgsrc itself was relatively unpopular, and running qmail from any sort of package was, as mentioned previously, strongly discouraged.)

2017: Definitely install from the pre-built 2017Q1 binary package

In late 2014, before everything went DESTDIR, I stopped managing packages from source directly on my server — it ate CPU, I/O, and disk space I preferred to allocate to serving — and started building binaries in a VM on my local development machine. Since I had chosen to generate binary packages, I had to configure qmail to build with numeric user and group IDs matching those already present on my server.

A couple weeks ago, trying to help my friend, I turned up a patch by Paul Fox that taught an early version of qmail to look up its numeric IDs at runtime. Using my growing C skills, I ported it forward and added it to pkgsrc (original).

With the patch, qmail’s compile process no longer needed any users or groups to exist. To also avoid needing them in the install process, I recorded the permissions qmail’s installer wanted to set, linked the installer with a fake chown() that does nothing, then applied pkgsrc’s mechanism for setting all the desired special permissions when installing a binary package. (I used the trick in Permanent CVS, temporary Git to work on a git branch, experiment freely, and keep only my best commits.)

I thought I was just about done solving my friend’s problem. On a test system, I cleaned out all vestiges of qmail having ever been there, then built and installed it. That’s when I noticed there was no queue.

Huh?

Oh.

I don’t remember slapping my forehead, which might not mean I didn’t.

After over a year of breakage, I finally noticed my nearly six-year-old mistake. Eager to fix it and ship it, and not seeing an elegant solution, I settled for a less elegant one. queue-fix is a third-party tool that reuses qmail’s code to repair or create a queue. I added it as a dependency and scripted it to create the queue if missing.

As far as I can tell, the result of naively installing our qmail binary package now matches file-for-file, permission-for-permission, what you’d get installing it from source by hand. Also, it works exactly as well as it always has for me in production. The triumphant pkgsrc commit message (original) concludes:

A typical binary package should now:

  1. Install on any other system of matching OS and architecture,
  2. Not need matching numeric UIDs and GIDs to do so, and
  3. Be usable in production.

You know, like any other binary package.

The latest soon-to-be-released pkgsrc stable branch will include production-ready qmail binary packages for many popular platforms. Especially if you’re on NetBSD, but also on other platforms, pkg_add qmail-run will make you wonder what all this fuss was ever about.

Exactly the point!

Once 2017Q1 is out, the main reasons I can think of not to get your qmail from our published binary packages are:

  1. You don’t use pkgsrc or NetBSD (or qmail)
  2. You don’t see a binary qmail package for your OS and architecture
  3. You need a qmail with non-default PKG_OPTIONS

With the default PKG_OPTIONS, you’ll get netqmail with Christopher K. Davis’s oversize DNS and Paul Jarc’s realrcptto patches.

2017/04/04 Update: Here’s the 2017Q1 release announcement.

2017/04/10 Update: Binary qmail packages aren’t showing up in the usual places. A dependency on checkpassword — which, not being under any license, is not under one of the licenses pkgsrc deems acceptable by default — is preventing bulk builds from publishing qmail binaries. On the off chance DJB intends to include checkpassword in the list of software he has placed in the public domain, I’ve emailed to request that he do so now. In the meanwhile, I’ve removed the checkpassword dependency (original) and requested the change be applied to the 2017Q1 branch. When it’s been applied, we should start seeing qmail binary packages. Likewise qmail-run and its dependency on ofmipd from mess822, which I made optional, off by default (original).

2017/04/18 Update: Binary packages are here! Running qmail on NetBSD takes two minutes.

Why did I make this effort?

My mail server had been running fine before. As far as I can tell, it’s running exactly as fine now.

My friend who likes qmail is having trouble convincing himself it’s still practical to run his own mail server at all.

My friend who wonders why I stick with qmail, were he to read this, would surely be feeling a renewed sense of wonder right about now.

I’m not. I’ve long been investing myself in NetBSD, pkgsrc, and qmail, and they continue to feel like good investments. Someday there may be a new effect I want to accomplish with qmail whose marginal cost I won’t enjoy paying. When that happens, I’ll reevaluate alternatives and the cost of switching to them.

In the meanwhile, next time I install qmail, I’m happy to say there’s an excellent chance none of the experience and expertise that went into the writing of this post will be called for. Having shipped working code, I get to evict some longstanding want-to-dos and oh-yeah-that-weird-things from residence in my brain (and cruft from my weekly build config), and I get positive reinforcement that further improvements are also worth trying for. Both of these have the effect of increasing my overall area under the curve.

The more I can simplify and automate, the fewer attention-slices I can require of myself, the more likely my desired outcomes persist when my circumstances change. That’s pretty important to me right about now.

What I might do next

qmail lets the names of its users and groups be configured at build time. pkgsrc could pretty easily support this, retaining the current names as defaults.

Some of qmail’s attendant packages can optionally build with patches to add IPv6 support. Enabling IPv6 mail service would require at least an optional patch to qmail itself.

Patches and/or wrapper programs exist to implement Sender Policy Framework, Sender Rewriting Scheme, and DomainKeys Identified Mail. It may be useful to optionally include them.

Update: account names are configurable (original) and SRS is optional (original).

What you might do next

What do you think? Could you benefit from applying some of these DevOps tools and practices? I’m teaching a hands-on workshop at the upcoming Agile Alliance Technical Conference where you can learn them. And/or teach me how I can benefit from letting go of qmail. ;-)