All posts by John Goerzen

An old DOS BBS in a Docker container

Awhile back, I wrote about my Debian Docker base images. I decided to extend this concept a bit further: to running DOS applications in Docker.

But first, a screenshot:

It turns out this is possible, but difficult. I went through all three major DOS emulators available (dosbox, qemu, and dosemu). I got them all running inside the Docker container, but had a number of, er, fun issues to resolve.

The general thing one has to do here is present a fake modem to the DOS environment. This needs to be exposed outside the container as a TCP port. That much is possible in various ways — I wound up using tcpser. dosbox had a TCP modem interface, but it turned out to be too buggy for this purpose.

The challenge comes in where you want to be able to accept more than one incoming telnet (or TCP) connection at a time. DOS was not a multitasking operating system, so there were any number of hackish solutions back then. One might have had multiple physical computers, one for each incoming phone line. Or they might have run multiple pseudo-DOS instances under a multitasking layer like DESQview, OS/2, or even Windows 3.1.

(Side note: I just learned of DESQview/X, which integrated DESQview with X11R5 and replaced the Windows 3 drivers to allow running Windows as an X application).

For various reasons, I didn’t want to try running one of those systems inside Docker. That left me with emulating the original multiple physical node setup. In theory, pretty easy — spin up a bunch of DOS boxes, each using at most 1MB of emulated RAM, and go to town. But here came the challenge.

In a multiple-physical-node setup, you need some sort of file sharing, because your nodes have to access the shared message and file store. There were a myriad of clunky ways to do this in the old DOS days – Netware, LAN manager, even some PC NFS clients. I didn’t have access to Netware. I tried the Microsoft LM client in DOS, talking to a Samba server running inside the Docker container. This I got working, but the LM client used so much RAM that, even with various high memory tricks, BBS software wasn’t going to run. I couldn’t just mount an underlying filesystem in multiple dosbox instances either, because dosbox did caching that wasn’t going to be compatible.

This is why I wound up using dosemu. Besides being a more complete emulator than dosbox, it had a way of sharing the host’s filesystems that was going to work.

So, all of this wound up with this: jgoerzen/docker-bbs-renegade.

I also prepared building blocks for others that want to do something similar: docker-dos-bbs and the lower-level docker-dosemu.

As a side bonus, I also attempted running this under Joyent’s Triton (SmartOS, Solaris-based). I was pleasantly impressed that I got it all almost working there. So yes, a Renegade DOS BBS running under a Linux-based DOS emulator in a container on a Solaris machine.

The Yellow House Phone Company (Featuring Asterisk and an 11-year-old)

“Well Jacob, do you think we should set up our own pretend phone company in the house?”

“We can DO THAT?”

“Yes!”

“Then… yes. Yes! YES YES YESYESYESYES YES! Let’s do it, dad!”

Not long ago, my parents had dug up the old phone I used back in the day. We still have a landline, and Jacob was having fun discovering how an analog phone works. I told him about the special number he could call to get the time and temperature read out to him. He discovered what happens if you call your own number and hang up. He figured out how to play “Mary Had a Little Lamb” using touchtone keys (after a slightly concerned lecture from me setting out some rules to make sure his “musical dialing” wouldn’t result in any, well, dialing.)

He was hooked. So I thought that taking it to the next level would be a good thing for a rainy day. I have run Asterisk before, though I had unfortunately gotten rid of most of my equipment some time back. But I found a great deal on a Cisco 186 ATA (Analog Telephone Adapter). It has two FXS lines (FXS ports simulate the phone company, and provide dialtone and ring voltage to a connected phone), and of course hooks up to the LAN.

We plugged that in, and Jacob was amazed to see its web interface come up. I had to figure out how to configure it (unfortunately, it uses SCCP rather than SIP, and figuring out Asterisk’s chan_skinny took some doing, but we got there.)

I set up voicemail. He loved it. He promptly figured out how to record his own greetings. We set up a second phone on the other line, so he could call between them. The cordless phones in our house support SIP, so I configured one of them as a third line. He spent a long time leaving himself messages.

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Pretty soon we both started having ideas. I set up extension 777, where he could call for the time. Then he wanted a way to get the weather forecast. Well, weather-util generates a text-based report. With it, a little sed and grep tweaking, the espeak TTS engine, and a little help from sox, I had a shell script worked up that would read back a forecast whenever he called a certain extension. He was super excited! “That’s great, dad! Can it also read weather alerts too?” Sure! weather-util has a nice option just for that. Both boys cackled as the system tried to read out the NWS header (their timestamps like 201711031258 started with “two hundred one billion…”)

Then I found an online source for streaming NOAA Weather Radio feeds – Jacob enjoys listening to weather radio – and I set up another extension he could call to listen to that. More delight!

But it really took off when I asked him, “Would you like to record your own menu?” “You mean those things where it says press 1 or 2 for this or that?” “Yes.” “WE CAN DO THAT?” “Oh yes!” “YES, LET’S DO IT RIGHT NOW!”

So he recorded a menu, then came and hovered by me while I hacked up extensions.conf, then eagerly went back to the phone to try it. Oh the excitement of hearing hisown voice, and finding that it worked! Pretty soon he was designing sub-menus (“OK Dad, so we’ll set it up so people can press 2 for the weather, and then choose if they want weather radio or the weather report. I’m recording that now. Got it?”)

He has informed me that next Saturday we will build an intercom system “like we have at school.” I’m going to have to have some ideas on how to tie Squeezebox in with Asterisk to make that happen, I think. Maybe this will do.

Switching to xmonad + Gnome – and ditching a Mac

I have been using XFCE with xmonad for years now. I’m not sure exactly how many, but at least 6 years, if not closer to 10. Today I threw in the towel and switched to Gnome.

More recently, at a new job, I was given a Macbook Pro. I wasn’t entirely sure what to think of this, but I thought I’d give it a try. I found MacOS to be extremely frustrating and confining. It had no real support for a tiling window manager, and although projects like amethyst tried to approximate what xmonad can do on Linux, they were just too limited by the platform and were clunky. Moreover, the entire UI was surprisingly sluggish; maybe that was an induced effect from animations, but I don’t think that explains it. A Debisn stretch install, even on inferior hardware, was snappy in a way that MacOS never was. So I have requested to swap for a laptop that will run Debian. The strange use of Command instead of Control for things, combined with the overall lack of configurability of keybindings, meant that I was going to always be fighting muscle memory moving from one platform to another. Not only that, but being back in the world of a Free Software OS means a lot.

Now then, back to xmonad and XFCE situation. XFCE once worked very well with xmonad. Over the years, this got more challenging. Around the jessie (XFCE 4.10) time, I had to be very careful about when I would let it save my session, because it would easily break. With stretch, I had to write custom scripts because the panel wouldn’t show up properly, and even some application icons would be invisible, if things were started in a certain order. This took much trial and error and was still cumbersome.

Gnome 3, with its tightly-coupled Gnome Shell, has never been compatible with other window managers — at least not directly. A person could have always used MATE with xmonad — but a lot of people that run XFCE tend to have some Gnome 3 apps (for instance, evince) anyhow. Cinnamon also wouldn’t work with xmonad, because it is simply another tightly-coupled shell instead of Gnome Shell. And then today I discovered gnome-flashback. gnome-flashback is a Gnome 3 environment that uses the traditional X approach with a separate window manager (metacity of yore by default). Sweet.

It turns out that Debian’s xmonad has built-in support for it. If you know the secret: apt-get install gnome-session-flashback (OK, it’s not so secret; it’s even in xmonad’s README.Debian these days) Install that, plus gnome and gdm3 and things are nice. Configure xmonad with GNOME support and poof – goodness right out of the box, selectable from the gdm sessions list.

I still have some gripes about Gnome’s configurability (or lack thereof). But I’ve got to say: This environment is the first one I’ve ever used that got external display switching very nearly right without any configuration, and I include MacOS in that. Plug in an external display, and poof – it’s configured and set up. You can hit a toggle key (Windows+P by default) to change the configurations, or use the Display section in gnome-control-center. Unplug it, and it instantly reconfigures itself to put everything back on the laptop screen. Yessss! I used to have scripts to do this in the wheezy/jessie days. XFCE in stretch had numerous annoying failures in this area which rendered the internal display completely dark until the next reboot – very frustrating. With Gnome, it just works. And, even if you have “suspend on lid closed” turned on, if the system is powered up and hooked up to an external display, it will keep running even if the lid is closed, figuring you must be using it on the external screen. Another thing the Mac wouldn’t do well.

All in all, some pretty good stuff here. I continue to be impressed by stretch. It is darn impressive to put this OS on generic hardware and have it outshine the closed-ecosystem Mac!

The Joy of Exploring: Old Phone Systems, Pizza, and Discovery

This story involves boys pretending to be pizza deliverymen using a working automated Strowger telephone exchange demonstrator on display in a museum, which is very old and is, to my knowledge, the only such working exhibit in the world. (Yes, I have video.) But first, a thought on exploration.

There are those that would say that there is nothing left to explore anymore – that the whole earth is mapped, photographed by satellites, and, well, known.

I prefer to look at it a different way: the earth is full of places that billions of people will never see, and probably don’t even know about. Those places may be quiet country creeks, peaceful neighborhoods one block away from major tourist attractions, an MTA museum in Brooklyn, a state park in Arkansas, or a beautiful church in Germany.

Martha is not yet two months old, and last week she and I spent a surprisingly long amount of time just gazing at tree branches — she was mesmerized, and why not, because to her, everything is new.

As I was exploring in Portland two weeks ago, I happened to pick up a nearly-forgotten book by a nearly-forgotten person, Beryl Markham, a woman who was a pilot in Africa about 80 years ago. The passage that I happened to randomly flip to in the bookstore, which really grabbed my attention, was this:

The available aviation maps of Africa in use at that time all bore the cartographer’s scale mark, ‘1/2,000,000’ — one over two million. An inch on the map was about thitry-two miles in the air, as compared to the flying maps of Europe on which one inch represented no more than four air miles.

Moreover, it seemed that the printers of the African maps had a slightly malicious habit of including, in large letters, the names of towns, junctions, and villages which, while most of them did exist in fact, as a group of thatched huts may exist or a water hold, they were usually so inconsequential as completely to escape discovery from the cockpit.

Beyond this, it was even more disconcerting to examine your charts before a proposed flight only to find that in many cases the bulk of the terrain over which you had to fly was bluntly marked: ‘UNSURVEYED’.

It was as if the mapmakers had said, “We are aware that between this spot and that one, there are several hundred thousands of acres, but until you make a forced landing there, we won’t know whether it is mud, desert, or jungle — and the chances are we won’t know then!”

— Beryl Markham, West With the Night

My aviation maps today have no such markings. The continent is covered with radio beacons, the world with GPS, the maps with precise elevations of the ground and everything from skyscrapers to antenna towers.

And yet, despite all we know, the world is still a breathtaking adventure.

Yesterday, the boys and I were going to fly to Abilene, KS, to see a museum (Seelye Mansion). Circumstances were such that we neither flew, nor saw that museum. But we still went to Abilene, and wound up at the Museum of Independent Telephony, a wondrous place for anyone interested in the history of technology. As it is one of those off-the-beaten-path sorts of places, the boys got 2.5 hours to use the hands-on exhibits of real old phones, switchboards, and also the schoolhouse out back. They decided — why not? — to use this historic equipment to pretend to order pizzas.

Jacob and Oliver proceeded to invent all sorts of things to use the phones for: ordering pizza, calling the cops to chase the pizza delivery guys, etc. They were so interested that by 2PM we still hadn’t had lunch and they claimed “we’re not hungry” despite the fact that we were going to get pizza for lunch. And I certainly enjoyed the exhibits on the evolution of telephones, switching (from manual plugboards to automated switchboards), and such.

This place was known – it even has a website, I had been there before, and in fact so had the boys (my parents took them there a couple of years ago). But yesterday, we discovered the Strowger switch had been repaired since the last visit, and that it, in fact, is great for conversations about pizza.

Whether it’s seeing an eclipse, discovering a fascination with tree branches, or historic telephones, a spirit of curiosity and exploration lets a person find fun adventures almost anywhere.

The Eclipse

Highway US-81 in northern Kansas and southern Nebraska is normally a pleasant, sleepy sort of drive. It was upgraded to a 4-lane road not too long ago, but as far as 4-lane roads go, its traffic is typically light. For drives from Kansas to South Dakota, it makes a pleasant route.

Yesterday was eclipse day. I strongly suspect that highway 81 had more traffic that day than it ever has before, or ever will again. For nearly the entire 3-hour drive to Geneva, NE, it was packed — though mostly still moving at a good speed. And for our entire drive back, highway 81 and every other southbound road we used was so full it felt like rush hour in Dallas. (Well, not quite. Traffic was still moving.) I believe scenes like this were played out across the continent.

I’ve been taking a lot of photos, and writing about our new baby Martha lately. Now it’s time to write a bit about some more adventures with Jacob and Oliver – they’re now in third and fifth grades in school.

We had been planning to fly, and airports I called were either full, or were planning to park planes in the grass, or even shut down some runways to use for parking. The airport in the little town of Beatrice, NE (which I had visited twice before) was even going to have a temporary FAA control tower. At the last minute, due to some storm activity near home at departure time, we unloaded the plane and drove instead.

The atmosphere at the fairgrounds in Geneva was festive. One family had brought bubbles for their kids — and extras to share.

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I had bought the boys a book about the eclipse, which they were reading before and during the event. They were both great, safe users of their eclipse glasses.

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Jacob caught a toad, and played with it for awhile. He wanted to bring it home with us, but I convinced him to let me take a picture of him with his toad friend instead.

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While we were waiting for totality, a number of buses from the local school district arrived. So by the time the big moment arrived, we could hear the distant roar of delight and applause from the school children gathered at the far end of the field, plus all the excitement nearby. Both boys were absolutely ecstatic to be witnessing it (and so was I!) “Wow!” “Awesome!” And simple cackles of delight were heard. On the drive home, they both kept talking about how amazing it was, and it was “once in a lifetime.”

We enjoyed our “eclipse neighbors” – the woman from San Antonio next to us, the surprise discovery of another family from just a few miles from us parked two cars down, even running into relatives at a restaurant on the way home. The applause from all around when it started – and when it ended. And the feeling, which is hard to describe, of awe and amazement at the wonders of our world and our universe.

There are many problems with the world right now, but somehow there’s something right about people coming together from all over to enjoy it.

A new baby and deep smiles

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A month ago, we were waiting for our new baby; time seemed to stand still. Now she is here! Martha Goerzen was born recently, and she is doing well and growing! Laura and I have enjoyed moments of cuddling her, watching her stare at our faces, hearing her (hopefully) soft sounds as she falls asleep in our arms. It is also heart-warming to see Martha’s older brothers take such an interest in her. Here is the first time Jacob got to hold her:

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Oliver, who is a boy very much into sports, play involving police and firefighters, and such, has started adding “aww” and “she’s so cute!” to his common vocabulary. He can be very insistent about interrupting me to hold her, too.

Time, Frozen

We’re expecting a baby any time now. The last few days have had an odd quality of expectation: any time, our family will grow.

It makes time seem to freeze, to stand still.

We have Jacob, about to start fifth grade and middle school. But here he is, still a sweet and affectionate kid as ever. He loves to care for cats and seeks them out often. He still keeps an eye out for the stuffed butterfly he’s had since he was an infant, and will sometimes carry it and a favorite blanket around the house. He will also many days prepare the “Yellow House News” on his computer, with headlines about his day and some comics pasted in — before disappearing to play with Legos for awhile.

And Oliver, who will walk up to Laura and “give baby a hug” many times throughout the day — and sneak up to me, try to touch my arm, and say “doink” before running off before I can “doink” him back. It was Oliver that had asked for a baby sister for Christmas — before he knew he’d be getting one!

In the past week, we’ve had out the garden hose a couple of times. Both boys will enjoy sending mud down our slide, or getting out the “water slide” to play with, or just playing in mud. The rings of dirt in the bathtub testify to the fun that they had. One evening, I built a fire, we made brats and hot dogs, and then Laura and I sat visiting and watching their water antics for an hour after, laughter and cackles of delight filling the air, and cats resting on our laps.

These moments, or countless others like Oliver’s baseball games, flying the boys to a festival in Winfield, or their cuddles at bedtime, warm the heart. I remember their younger days too, with fond memories of taking them camping or building a computer with them. Sometimes a part of me wants to just keep soaking in things just as they are; being a parent means both taking pride in children’s accomplishments as they grow up, and sometimes also missing the quiet little voice that can be immensely excited by a caterpillar.

And yet, all four of us are so excited and eager to welcome a new life into our home. We are ready. I can’t wait to hold the baby, or to lay her to sleep, to see her loving and excited older brothers. We hope for a smooth birth, for mom and baby.

Here is the crib, ready, complete with a mobile with a cute bear (and even a plane). I can’t wait until there is a little person here to enjoy it.

First Experiences with Stretch

I’ve done my first upgrades to Debian stretch at this point. The results have been overall good. On the laptop my kids use, I helped my 10-year-old do it, and it worked flawlessly. On my workstation, I got a kernel panic on boot. Hmm.

Unfortunately, my system has to use the nv drivers, which leaves me with an 80×25 text console. It took some finagling (break=init in grub, then manually insmoding the appropriate stuff based on modules.dep for nouveau), but finally I got a console so I could see what was breaking. It appeared that init was crashing because it couldn’t find liblz4. A little digging shows that liblz4 is in /usr, and /usr wasn’t mounted. I’ve filed the bug on systemd-sysv for this.

I run root on ZFS, and further digging revealed that I had datasets named like this:

  • tank/hostname-1/ROOT
  • tank/hostname-1/usr
  • tank/hostname-1/var

This used to be fine. The mountpoint property of the usr dataset put it at /usr without incident. But it turns out that this won’t work now, unless I set ZFS_INITRD_ADDITIONAL_DATASETS in /etc/default/zfs for some reason. So I renamed them so usr was under ROOT, and then the system booted.

Then I ran samba not liking something in my bind interfaces line (to be fair, it did still say eth0 instead of br0). rpcbind was failing in postinst, though a reboot seems to have helped that. More annoying was that I had trouble logging into my system because resolv.conf was left empty (despite dns-* entries in /etc/network/interfaces and the presence of resolvconf). I eventually repaired that, and found that it kept removing my “search” line. Eventually I removed resolvconf.

Then mariadb’s postinst was silently failing. I eventually discovered it was sending info to syslog (odd), and /etc/init.d/apparmor teardown let it complete properly. It seems like there may have been an outdated /etc/apparmor.d/cache/usr.sbin.mysql out there for some reason.

Then there was XFCE. I use it with xmonad, and the session startup was really wonky. I had to zap my sessions, my panel config, etc. and start anew. I am still not entirely sure I have it right, but I at do have a usable system now.

Fixing the Problems with Docker Images

I recently wrote about the challenges in securing Docker container contents, and in particular with keeping up-to-date with security patches from all over the Internet.

Today I want to fix that.

Besides security, there is a second problem: the common way of running things in Docker pretends to provide a traditional POSIX API and environment, but really doesn’t. This is a big deal.

Before diving into that, I want to explain something: I have often heard it said the Docker provides single-process containers. This is unambiguously false in almost every case. Any time you have a shell script inside Docker that calls cp or even ls, you are running a second process. Web servers from Apache to whatever else use processes or threads of various types to service multiple connections at once. Many Docker containers are single-application, but a process is a core part of the POSIX API, and very little software would work if it was limited to a single process. So this is my little plea for more precise language. OK, soapbox mode off.

Now then, in a traditional Linux environment, besides your application, there are other key components of the system. These are usually missing in Docker containers.

So today, I will fix this also.

In my docker-debian-base images, I have prepared a system that still has only 11MB RAM overhead, makes minimal changes on top of Debian, and yet provides a very complete environment and API. Here’s what you get:

  • A real init system, capable of running standard startup scripts without modification, and solving the nasty Docker zombie reaping problem.
  • Working syslog, which can either export all logs to Docker’s logging infrastructure, or keep them within the container, depending on your preferences.
  • Working real schedulers (cron, anacron, and at), plus at least the standard logrotate utility to help prevent log files inside the container from becoming huge.

The above goes into my “minimal” image. Additional images add layers on top of it, and here are some of the features they add:

  • A real SMTP agent (exim4-daemon-light) so that cron and friends can actually send you mail
  • SSH client and server (optionally exposed to the Internet)
  • Automatic security patching via unattended-upgrades and needsrestart

All of the above, including the optional features, has an 11MB overhead on start. Not bad for so much, right?

From here, you can layer on top all your usual Dockery things. You can still run one application per container. But you can now make sure your disk doesn’t fill up from logs, run your database vacuuming commands at will, have your blog download its RSS feeds every few minutes, etc — all from within the container, as it should be. Furthermore, you don’t have to reinvent the wheel, because Debian already ships with things to take care of a lot of this out of the box — and now those tools will just work.

There is some popular work done in this area already by phusion’s baseimage-docker. However, I made my own for these reasons:

  • I wanted something based on Debian rather than Ubuntu
  • By using sysvinit rather than runit, the OS default init scripts can be used unmodified, reducing the administrative burden on container builders
  • Phusion’s system is, for some reason, not auto-built on the Docker hub. Mine is, so it will be automatically revised whenever the underlying Debian system, or the Github repository, is.

Finally a word on the choice to use sysvinit. It would have been simpler to use systemd here, since it is the default in Debian these days. Unfortunately, systemd requires you to poke some holes in the Docker security model, as well as mount a cgroups filesystem from the host. I didn’t consider this acceptable, and sysvinit ran without these workarounds, so I went with it.

With all this, Docker becomes a viable replacement for KVM for various services on my internal networks. I’ll be writing about that later.

Family Spring: A Story in Photos

This has been a spring with times to relax, times to be busy, times of anticipation of a new baby, and times of enjoying our family.

Rather than write a lot of words about it, I’m telling the story in photos.

To view, click here, then click Show Info in the upper right to see captions. You can pause it with the button in the lower left, and use arrow keys to advance.

Alternatively, there’s a captionless slideshow available here.

Here’s one photo to get you started:

Happy about the little sister on the way