My life with Coherent, part 2

In the first post of these series I've shown you it's possible to make Coherent 4.2.10 run under the newest version of QEMU. Now it's time to take it one step further.

I've had permission from Robert Swartz himself to distribute the first perfectly legal Coherent 4.2.10 QEMU image as long as you comply with the following conditions:

You may use the software on this image free of charge for personal, non-commercial use. You may NOT redistribute this image or the software it contains without written permission from the copyright holder. The software is provided on an "as is" basis without warranty of any kind.

Getting started
Download and unpack the archive. Included are two images, coherent.public.img and fat16.dd. The first one contains the Coherent image, the second one an empty floppy. If you want to, you can start them right away:

qemu-system-i386 -hda coherent.public.img -fda fat16.dd -m 16

First, don't try to crank up the amount of memory, Coherent won't use it - at least not this kernel. Second, you just have to be patient to attempt this, because it may take up to 10 minutes before Coherent is up and running. The good news is that you can monitor how far it is by pressing [CTRL]-[ALT]-2 in QEMU and typing:

info blockstats

If rd_bytes reaches 600,000 you can probably login. There are two login entries, the obvious root with password rootroot and a normal user named habe with password habehabe. Pick any one.

When you've logged in you might want to try the usual stuff like ls -l or ps -eaf, maybe you're even so bold to start up vi or cc. In any case, you will find that everything is painfully slow. If you want to get out, you can do so, but you'll have to be root in order to do it properly. Just issue:

cd; /etc/shutdown halt 0

Note it doesn't shutdown immediately! You'll have to wait until Coherent tells you it's safe to power down. Be patient! You can also exit QEMU without shutting down, but in that case you may have corrupted your image. And believe me, at these speeds you do not want to run fsck..

So that's it? Coherent runs, but it is completely unusable? No, not quite. Coherent does some disk caching, so after a while it becomes responsive. That is: until you reboot. But how can you avoid a reboot? Well, it's quite simple. QEMU allows you to make snapshots, so if you need Coherent you don't boot it, but simply load the snapshot.

QEMU only allows snapshots when you're using the so called "qcow2" image type, so we have to convert the files you just downloaded. That's not too hard, since QEMU comes with a handy utility for that. Just issue:

qemu-img convert -c -O qcow2 coherent.public.img Coherent.dsk
qemu-img convert -c -O qcow2 fat16.dd fat16.dsk

The latter may give you a warning, but don't worry, we'll only use it as a placeholder. Ok, we're done, let's start it up again:

qemu-system-i386 -hda Coherent.dsk -fda fat16.dsk -m 16

Agreed, you're in for the same wait. Sorry for that. But I promise you next time it'll be much faster. Just stay with me for a little while longer. When Coherent comes up, log in as usual. Then press [CTRL]-[ALT]-2 to enter the monitor. Now type:

savevm test0

This will save the current state of Coherent in a QEMU snapshot, so you'll end up here next time you start it. Return to the emulation by pressing [CTRL]-[ALT]-1 fiddle around a little bit, start up your favorite commands a few times and then save a new snapshot:

savevm test1

Shutdown Coherent properly and start it again, but this time with the command:

qemu-system-i386 -hda Coherent.dsk -fda fat16.dsk -m 16 -loadvm test1

Ok, that's more like it, isn't it? Ok, shut it down again. This time you'll be able to start it up much faster. Let's try something fancy now and invoke QEMU with:

qemu-system-i386 -hda Coherent.dsk -fda fat16.dsk -m 16 -serial telnet:localhost:4444,server,nowait -loadvm test1

Log in as root and type:

enable /dev/com1l

Now start up a terminal session on your host and type:

telnet localhost 4444

Yes, you can login to Coherent from your host Operating System. But that's about everything you can do as far as networking under Coherent is concerned.

There is a full TCP/IP stack available for Coherent, but you'll need a special kernel in order to make it work - which doesn't seem to be available. So I haven't succeeded to do much more in this area. If you have, please leave a comment.



Installing Coherent
Maybe you'll think this small system is so much fun that you want to give it a permanent place on your desktop. That is where the coherent.sh script comes in. It works with both KDE (KDialog) and Gnome (Zenity) and it makes it easier to launch the QEMU/Coherent combination. The only thing you have to do is to state where your disks are located:

COHAT0A=/opt/qemu/coherent.dsk
COHFD0=/opt/qemu/null.dsk

If you want to exchange files between Coherent and your host, you'll have to change /etc/fstab as well:

/opt/qemu/fat16.dd /mnt/coherent msdos rw,user,noauto,loop 0 0

Note this is the uncompressed, original file! You can mount the uncompressed Coherent image as well (as sysv), but you won't be able to write to it. I don't think I'll have to tell you how to mount a floppy image, do I? Once the VM is up and running you can exchange the virtual, empty floppy for the raw version by switching to the QEMU monitor and issuing:

change floppy0 fat16.dd

However, while the raw floppy is online you can't make a snapshot. When you want to take a snapshot you simply return to the dummy floppy by issuing:

change floppy0 fat16.dsk

Ok, now we've cleared that one we can concentrate on the real issue here: how do we get any files from the floppy? That's not as difficult as you think. You'll only need to edit one file, /etc/default/msdos. Make sure the appropriate section reads:

# This is for a system with a 3.5 inch A drive and a 5.25 inch B drive
a=/dev/fva0
a9=/dev/fqa0
b=/dev/fha1
b9=/dev/f9a1

And you're ready to rock 'n roll. There is a whole slew of MS-DOS related commands at your disposal like:

• dosls
• doscp
• dosrm
• dosrmdir

E.g. copying the /etc/default/msdos file to the floppy is simply:

doscp /etc/default/msdos a:

And copying it back is done by:

doscp a:/msdos /etc/default

Well, that ain't rocket science, is it? We can use it right away to fix some Y2K issues. Yes, this version of Coherent won't go past the 31st of December 1999, but it is easily fixed by ATclock and date. Copy them to the /bin directory and reboot. That'll fix it.

You may also be tempted to try another kernel. Several ones are available here. Just copy it to the root and hard-link it to autoboot, e.g.:

ln cohat0 autoboot

Note you can also select a kernel when starting up - just press [SPACE] immediately. Coherent will answer:

If installing COHERENT, please type "begin".

But it is actually a prompt for the kernel name. Obviously, if you type autoboot it will boot the default kernel - just in case you don't know how to get out of there ;-)

Final notes

• Although Coherent comes with a full fledged C compiler, it won't compile your ANSI-C sources, since it is strictly K&R C. However, GCC - and all the GNU stuff that comes along with it - is available. Still, I like the little beast, since it makes small and fast compilants.
• Coherent does have virtual consoles. Press [CTRL]-[NUM0], [CTRL]-[NUM1], etc.
• The archives of comp.os.coherent are compelling reading, featuring Linus Torvalds on who's got the best OS.
• Additional notes and links on the subject are appreciated. Just leave them in the comments.

Useful links
Good sources for additional software are:

• http://main2.amu.edu.pl/~apopiele/embed.html
• http://www.landibase.com/coherent.html
• ftp://ftp.mayn.de/pub/really_old_stuff/coherent/
• gopher://telefisk.org/1/coherent

Additional information can be obtained:

• Coherent OS newsgroup
• Wikipedia
• My life with Coherent, part 1

Hollywood still doesn't get it

The Dutch Anti-Piracy organization "Brein" has decided to sue ISP's UPC, KPN, T-Mobile and Tele2 after their recent victory in court. I really don't understand why. First of all, blocking a handful of IP addresses hasn't had any effect at all.

But most of all, if you really want to fight piracy you got to have support from the public. And that support is crumbling with each and every effort to enforce compliance to that 10 minutes of pesky messages you get when you insert a "legal" DVD. Yeah, you name them all: SOPA, PIPA, ACTA or whatever they may be called. Crowds are cheering on the streets and can't wait to have them ratified.

Metallica, once one of the most fierce fighters of piracy, has seen the sign on the wall and radically changed its position. These guys are not stupid. They know their stand on piracy affected their popularity, so they took the only decision they could take.

I've never been a downloader. I simply don't like the hassle that comes with it. But I have friends who are. One of them is a gray haired hippie, who also happens to be a record collector. Consequently, a burned CD has little value to him. But he is also a great fan of vintage science fiction movies. You hardly find those movies in the local stores and when you do the prices are outrageous. So every now and then he ordered one at Amazon. When you add all the additional costs they're not quite cheap either.

So when he wanted "to go on the Internet" in the early 2000's I told him to buy a Mac and get XS4ALL. A whole new world opened up to him. One night when we were having an beer and he told me how hard it was to get a decent copy of "Jason and the Argonauts" for a reasonable price. So I introduced him to the world of torrents, clearly stating that although downloading wasn't illegal in the Netherlands, it wasn't quite legal as well.

"Unlawful" isn't black and white down here, but has quite a few shades of gray. E.g. contrary to popular belief marijuana isn't legal here, it's just not.. completely illegal. It's - as we Dutch say - "condoned", which means you aren't prosecuted.

We quickly found a viable torrent and started downloading. It trickled down at about 10 kB/s, but he wasn't in a hurry. And a day or so later it was there. The weeks that followed he went into a kind of download frenzy, but then it settled down. I mean, they don't make movies like that anymore and the more recent ones you can get in the shop.

We met on the street a few weeks ago and we quickly landed on the subject of the recent Ziggo/XS4ALL verdict. He was furious. "Who are they to tell me where I can or cannot surf?!" he said. I told him he still could. I told him to take a look at my blog and simply follow the links.

That evening he phoned me to say everything worked fine and he was currently downloading "Captain America, the first avenger". "I'm gonna boycott them!" he said "I spend about 20 Euros a week on DVD's and if this is how they're treating me, they're gonna lose a customer! That thing is in the store for about 15 Euros - that's too expensive for my taste, but I'm gonna watch it tonight! You won't believe the download speed I'm getting, about 500 kB/s!! It's even got Dutch subtitles!"

I wasn't surprised. Everyone knows that the more popular a title is, the more seeders and leechers are offering it, which really helps to speed up the download. He had already downloaded "The Thing 2", "The Green Lantern" and I'm sure more were coming. So that is in effect what Mr. Kuik, spokesman of "BREIN", achieved. And he's making himself more popular by the minute.

The point is that the entertainment industry seems to be unable to listen to their best customers. They want the world to play by their rules, but every enterpreneur knows that's a very bad business model. Studies prove that the entertainment industry can survive and even make money, but they simply have to start to use their brains ("BREIN" means "BRAIN" in Dutch).

One of these pioneers is "Iron Sky", that partly uses "crowd funding" to raise money. And they will offer the movie for download once it has been in the theatres. Now that's creative thinking. I won't say it will work, but at least they're trying. Most importantly, they have the support of the community.

In contrast, the music industry have tried to tie down their customers with DRM. Needless to say they failed miserably - as I predicted - and nowadays it is very hard to find a CD or download with DRM. It simply doesn't work that way, despite state-of-the-art technology and elaborate schemes to "hide" the disadvantages from DRM to the public.

Now they're relying again on technology to fight piracy, but this time the technology is not in their hands, so it is even easier to find a way around it. Technology has always been a double edged sword for Hollywood. The introduction of the TV almost brought it to its knees, CGI on the other hand, produced some of its most famous blockbusters.

However, it has to realize that the Internet is nothing more than the 21st century equivalent of the TV. It can't be controlled and you can't legislate it away. Hollywood will have to change its game. Mikhail Gorbachev once said "Those who come too late will be punished by life itself".

Hollywood may not realize it, but the Internet is not the last challenge it has to face. In 15, 20 years, may be sooner, every kid with a computer will be able to create his own Hollywood grade movies. There will be digitilized Marilyn Monroes, James Deans, Humphrey Bogarts, landscapes from all over the world, cars from every era. Of course, most of these movies will be very, very bad. But some of them will be great. Most important of all: they will be free. And when they're not ready for the Internet, they aren't prepared for that.

With the turn of the millennium I expected "20th Century Fox" to change its name. It didn't. Now I understand why.

My life with Coherent, part 1

In the early 1990ies my company switched from an S/36 system to a Unix system. No one had any knowledge of that "alien" platform, so I became the expert to be. It was not entirely voluntary: I either made it work or I was fired.

Needless to say I spend lots of time behind the terminal, but it just wasn't enough. Working behind a $100,000 machine on a root account while barely knowing what you were doing was kind of intimidating. I was simply too reluctant to perform the necessary experiments.

In order to get more time and a less intimidating environment I started looking for alternatives, but I quickly found out there were few options. There were some MS-DOS based products that allowed me to write shell scripts, but that just wasn't the real deal. Xenix and SCO were too expensive. And then I found out about Coherent.

Coherent is a full fledged Unix that runs on a simple 386 with a few megabytes of memory - incredible, but true. The kernel is just a few hundred KB, so it boots in an instant. It lived happy together with MS-DOS in its own 40 MB partition. But the best thing was its price: only $100. Needless to say I spend a lot of hours with that little beast, porting my C programs and UUCPing with that "monster" machine back at work.

But every machine comes to a grinding halt at some moment in time. Getting a new PC wasn't a problem, but when I tried to reinstall Coherent I found that it didn't support my new IDE drive. Too bad, but since I had become a proficient Unix system admin I really didn't need it anymore.

Still, with every new release of QEMU or VMware I tried to reinstall it - with little result. That is, until QEMU 0.14 was released. After the arduous task of installing Coherent it bombed out just before the final reboot. But the Dutch don't throw away things that easily. I didn't delete the image, instead I simply waited for the next iteration of QEMU.

When I started it, it seemed it hang right away, but the QEMU monitor told another story. It was still alive. It was reading the disk, but very, very slowly.

Hours later the login prompt appeared and I logged in. The whole thing worked, but it was very sluggish. After having worked with it for a little while it became a bit more responsive. It didn't take me too long to figure out it was the IDE emulation that was slowing it down, reading about 1K a second. But once a file was in cache there were hardly any performance issues.

However, when starting up Coherent performed an 'fsck', which made booting a bit tiresome - I assure you that reading 7 megs at 1 KB/s is no fun. The easiest thing was to remove the 'fsck' check, which was easy enough. A quick edit of 'brc' was sufficient. Now I could login after Coherent had read only 150 KB, which was a significant improvement.

But I still wasn't happy. Every time I rebooted I had an empty cache. There had to be another way. Yes, there was, but for that I had to turn to QEMU. QEMU allows you to make a snapshot of the whole virtual machine - memory, CPU, the whole shebang. That not only allowed me to "boot" instantly, but also with the disk cache intact. Ok, now we're talking!



Since the standard Coherent C compiler only supports K&R C, almost all my C programs have a "-DARCHAIC" switch, which enables K&R prototypes. Even after 15 years I still maintain them, so porting my 4tH compiler shouldn't be very difficult. It wasn't. In these 15 years after more than doubling the code base I had only made about 10 syntax errors, which were quickly fixed.

But still there was a problem. Sure, I could use a raw floppy image to exchange files between the host and the VM, but since you can't make a snaphot of a raw floppy I had to reboot the VM after each and every transfer, which kind of defeated the sense of making snapshots.

The solution was to startup the VM with a QCOW2 floppy, which served no other purpose than to define a floppy device in the VM. You can not easily mount a QCOW2 image and so it is consequently not very well suited for file transfer.

Once the VM is up and running you can exchange this virtual floppy for a raw version by switching to the QEMU monitor and issuing:

change floppy0 fat16.img

When you want to take a snapshot you simply return to the dummy floppy by issuing:

change floppy0 dummy.dsk

And subsequently save the snapshot by issuing:

savevm test0

After that I was ready to rock 'n roll. It took me about an hour or so to port my compiler and transfer the executables back to the host. Furthermore, I installed another more modern kernel, applied some Y2K patches and customized my Coherent 4.2 installation.

In the next part of this series I will describe this in more detail and - even better - give you the opportunity to try it for yourself. All perfectly legal, that is..!