This is a article on slashdot taking a look at the historical Linux Kerel 0.01:
LinuxFan writes “KernelTrap has a fascinating article about the first Linux kernel, version 0.01, complete with source code and photos of Linus Torvalds as a young man attending the University of Helsinki. Torvalds originally planned to call the kernel “Freax,” and in his first announcement noted, “I’m doing a (free) operating system (just a hobby, won’t be big and professional like gnu) for 386(486) AT clones.” He also stressed that the kernel was very much tied to the i386 processor, “simply, I’d say that porting is impossible.” Humble beginnings.”
Now for the real article itsel:
“This is a free minix-like kernel for i386(+) based AT-machines,” began the Linux version 0.01 release notes in September of 1991 for the first release of the Linux kernel. “As the version number (0.01) suggests this is not a mature product. Currently only a subset of AT-hardware is supported (hard-disk, screen, keyboard and serial lines), and some of the system calls are not yet fully implemented (notably mount/umount aren’t even implemented).” Booting the original 0.01 Linux kernel required bootstrapping it with minix, and the keyboard driver was written in assembly and hard-wired for a Finnish keyboard. The listed features were mostly presented as a comparison to minix and included, efficiently using the 386 chip rather than the older 8088, use of system calls rather than message passing, a fully multithreaded FS, minimal task switching, and visible interrupts. Linus Torvalds noted, “the guiding line when implementing linux was: get it working fast. I wanted the kernel simple, yet powerful enough to run most unix software.” In a section titled “Apologies :-)” he noted:
“This isn’t yet the ‘mother of all operating systems’, and anyone who hoped for that will have to wait for the first real release (1.0), and even then you might not want to change from minix. This is a source release for those that are interested in seeing what linux looks like, and it’s not really supported yet.”
Linus had originally intended to call the new kernel “Freax”. According to Wikipedia, the name Linux was actually invented by Ari Lemmke who maintained the ftp.funet.fi FTP server from which the kernel was originally distributed.
The initial post that Linus made about Linux was to the comp.os.minix Usenet group titled, “What would you like to see most in minix“. It began:
“I’m doing a (free) operating system (just a hobby, won’t be big and professional like gnu) for 386(486) AT clones. This has been brewing since april, and is starting to get ready. I’d like any feedback on things people like/dislike in minix, as my OS resembles it somewhat (same physical layout of the file-system (due to practical reasons) among other things).”
Later in the same thread, Linus went on to talk about how unportable the code was:
“Simply, I’d say that porting is impossible. It’s mostly in C, but most people wouldn’t call what I write C. It uses every conceivable feature of the 386 I could find, as it was also a project to teach me about the 386. As already mentioned, it uses a MMU, for both paging (not to disk yet) and segmentation. It’s the segmentation that makes it REALLY 386 dependent (every task has a 64Mb segment for code & data – max 64 tasks in 4Gb. Anybody who needs more than 64Mb/task – tough cookies).
“It also uses every feature of gcc I could find, specifically the __asm__ directive, so that I wouldn’t need so much assembly language objects. Some of my ‘C’-files (specifically mm.c) are almost as much assembler as C. It would be ‘interesting’ even to port it to another compiler (though why anybody would want to use anything other than gcc is a mystery).
“Unlike minix, I also happen to LIKE interrupts, so interrupts are handled without trying to hide the reason behind them (I especially like my hard-disk-driver. Anybody else make interrupts drive a state-machine?). All in all it’s a porters nightmare. “
Indeed, Linux 1.0 was released on March 13th, 1994 supporting only the 32-bit i386 architecture. However, by the release of Linux 1.2 on March 7th, 1995 it had already been ported to 32-bit MIPS, 32-bit SPARC, and the 64-bit Alpha. By the release of Linux 2.0 on June 9th, 1996 support had also been added for the 32-bit m68k and 32-bit PowerPC architectures. And jumping forward to the Linux 2.6 kernel, first released in 2004, it has been and continues to be ported to numerous additional architectures.
Linux 0.01 release notes:
Notes for linux release 0.01 0. Contents of this directory linux-0.01.tar.Z - sources to the kernel bash.Z - compressed bash binary if you want to test it update.Z - compressed update binary RELNOTES-0.01 - this file 1. Short intro This is a free minix-like kernel for i386(+) based AT-machines. Full source is included, and this source has been used to produce a running kernel on two different machines. Currently there are no kernel binaries for public viewing, as they have to be recompiled for different machines. You need to compile it with gcc (I use 1.40, don't know if 1.37.1 will handle all __asm__-directives), after having changed the relevant configuration file(s). As the version number (0.01) suggests this is not a mature product. Currently only a subset of AT-hardware is supported (hard-disk, screen, keyboard and serial lines), and some of the system calls are not yet fully implemented (notably mount/umount aren't even implemented). See comments or readme's in the code. This version is also meant mostly for reading - ie if you are interested in how the system looks like currently. It will compile and produce a working kernel, and though I will help in any way I can to get it working on your machine (mail me), it isn't really supported. Changes are frequent, and the first "production" version will probably differ wildly from this pre-alpha-release. Hardware needed for running linux: - 386 AT - VGA/EGA screen - AT-type harddisk controller (IDE is fine) - Finnish keyboard (oh, you can use a US keyboard, but not without some practise :-) The Finnish keyboard is hard-wired, and as I don't have a US one I cannot change it without major problems. See kernel/keyboard.s for details. If anybody is willing to make an even partial port, I'd be grateful. Shouldn't be too hard, as it's tabledriven (it's assembler though, so ...) Although linux is a complete kernel, and uses no code from minix or other sources, almost none of the support routines have yet been coded. Thus you currently need minix to bootstrap the system. It might be possible to use the free minix demo-disk to make a filesystem and run linux without having minix, but I don't know... 2. Copyrights etc This kernel is (C) 1991 Linus Torvalds, but all or part of it may be redistributed provided you do the following: - Full source must be available (and free), if not with the distribution then at least on asking for it. - Copyright notices must be intact. (In fact, if you distribute only parts of it you may have to add copyrights, as there aren't (C)'s in all files.) Small partial excerpts may be copied without bothering with copyrights. - You may not distibute this for a fee, not even "handling" costs. Mail me at [email blocked] if you have any questions. Sadly, a kernel by itself gets you nowhere. To get a working system you need a shell, compilers, a library etc. These are separate parts and may be under a stricter (or even looser) copyright. Most of the tools used with linux are GNU software and are under the GNU copyleft. These tools aren't in the distribution - ask me (or GNU) for more info. 3. Short technical overview of the kernel. The linux kernel has been made under minix, and it was my original idea to make it binary compatible with minix. That was dropped, as the differences got bigger, but the system still resembles minix a great deal. Some of the key points are: - Efficient use of the possibilities offered by the 386 chip. Minix was written on a 8088, and later ported to other machines - linux takes full advantage of the 386 (which is nice if you /have/ a 386, but makes porting very difficult) - No message passing, this is a more traditional approach to unix. System calls are just that - calls. This might or might not be faster, but it does mean we can dispense with some of the problems with messages (message queues etc). Of course, we also miss the nice features :-p. - Multithreaded FS - a direct consequence of not using messages. This makes the filesystem a bit (a lot) more complicated, but much nicer. Coupled with a better scheduler, this means that you can actually run several processes concurrently without the performance hit induced by minix. - Minimal task switching. This too is a consequence of not using messages. We task switch only when we really want to switch tasks - unlike minix which task-switches whatever you do. This means we can more easily implement 387 support (indeed this is already mostly implemented) - Interrupts aren't hidden. Some people (among them Tanenbaum) think interrupts are ugly and should be hidden. Not so IMHO. Due to practical reasons interrupts must be mainly handled by machine code, which is a pity, but they are a part of the code like everything else. Especially device drivers are mostly interrupt routines - see kernel/hd.c etc. - There is no distinction between kernel/fs/mm, and they are all linked into the same heap of code. This has it's good sides as well as bad. The code isn't as modular as the minix code, but on the other hand some things are simpler. The different parts of the kernel are under different sub-directories in the source tree, but when running everything happens in the same data/code space. The guiding line when implementing linux was: get it working fast. I wanted the kernel simple, yet powerful enough to run most unix software. The file system I couldn't do much about - it needed to be minix compatible for practical reasons, and the minix filesystem was simple enough as it was. The kernel and mm could be simplified, though: - Just one data structure for tasks. "Real" unices have task information in several places, I wanted everything in one place. - A very simple memory management algorithm, using both the paging and segmentation capabilities of the i386. Currently MM is just two files - memory.c and page.s, just a couple of hundreds of lines of code. These decisions seem to have worked out well - bugs were easy to spot, and things work. 4. The "kernel proper" All the routines handling tasks are in the subdirectory "kernel". These include things like 'fork' and 'exit' as well as scheduling and minor system calls like 'getpid' etc. Here are also the handlers for most exceptions and traps (not page faults, they are in mm), and all low-level device drivers (get_hd_block, tty_write etc). Currently all faults lead to a exit with error code 11 (Segmentation fault), and the system seems to be relatively stable ("crashme" hasn't - yet). 5. Memory management This is the simplest of all parts, and should need only little changes. It contains entry-points for some things that the rest of the kernel needs, but mostly copes on it's own, handling page faults as they happen. Indeed, the rest of the kernel usually doesn't actively allocate pages, and just writes into user space, letting mm handle any possible 'page-not-present' errors. Memory is dealt with in two completely different ways - by paging and segmentation. First the 386 VM-space (4GB) is divided into a number of segments (currently 64 segments of 64Mb each), the first of which is the kernel memory segment, with the complete physical memory identity-mapped into it. All kernel functions live within this area. Tasks are then given one segment each, to use as they wish. The paging mechanism sees to filling the segment with the appropriate pages, keeping track of any duplicate copies (created at a 'fork'), and making copies on any write. The rest of the system doesn't need to know about all this. 6. The file system As already mentioned, the linux FS is the same as in minix. This makes crosscompiling from minix easy, and means you can mount a linux partition from minix (or the other way around as soon as I implement mount :-). This is only on the logical level though - the actual routines are very different. NOTE! Minix-1.6.16 seems to have a new FS, with minor modifications to the 1.5.10 I've been using. Linux won't understand the new system. The main difference is in the fact that minix has a single-threaded file-system and linux hasn't. Implementing a single-threaded FS is much easier as you don't need to worry about other processes allocating buffer blocks etc while you do something else. It also means that you lose some of the multiprocessing so important to unix. There are a number of problems (deadlocks/raceconditions) that the linux kernel needed to address due to multi-threading. One way to inhibit race-conditions is to lock everything you need, but as this can lead to unnecessary blocking I decided never to lock any data structures (unless actually reading or writing to a physical device). This has the nice property that dead-locks cannot happen. Sadly it has the not so nice property that race-conditions can happen almost everywhere. These are handled by double-checking allocations etc (see fs/buffer.c and fs/inode.c). Not letting the kernel schedule a task while it is in supervisor mode (standard unix practise), means that all kernel/fs/mm actions are atomic (not counting interrupts, and we are careful when writing those) if you don't call 'sleep', so that is one of the things we can count on. 7. Apologies :-) This isn't yet the "mother of all operating systems", and anyone who hoped for that will have to wait for the first real release (1.0), and even then you might not want to change from minix. This is a source release for those that are interested in seeing what linux looks like, and it's not really supported yet. Anyone with questions or suggestions (even bug-reports if you decide to get it working on your system) is encouraged to mail me. 8. Getting it working Most hardware dependancies will have to be compiled into the system, and there a number of defines in the file "include/linux/config.h" that you have to change to get a personalized kernel. Also you must uncomment the right "equ" in the file boot/boot.s, telling the bootup-routine what kind of device your A-floppy is. After that a simple "make" should make the file "Image", which you can copy to a floppy (cp Image /dev/PS0 is what I use with a 1.44Mb floppy). That's it. Without any programs to run, though, the kernel cannot do anything. You should find binaries for 'update' and 'bash' at the same place you found this, which will have to be put into the '/bin' directory on the specified root-device (specified in config.h). Bash must be found under the name '/bin/sh', as that's what the kernel currently executes. Happy hacking. Linus Torvalds [email blocked] Petersgatan 2 A 2 00140 Helsingfors 14 FINLAND
First posting about Linux:
From: Linus Benedict Torvalds Newsgroups: comp.os.minix Subject: Gcc-1.40 and a posix-question Date: 3 Jul 91 10:00:50 GMT Hello netlanders, Due to a project I'm working on (in minix), I'm interested in the posix standard definition. Could somebody please point me to a (preferably) machine-readable format of the latest posix rules? Ftp-sites would be nice. As an aside for all using gcc on minix - the new version (1.40) has been out for some weeks, and I decided to test what needed to be done to get it working on minix (1.37.1, which is the version you can get from plains is nice, but 1.40 is better :-). To my surpice, the answer turned out to be - NOTHING! Gcc-1.40 compiles as-is on minix386 (with old gcc-1.37.1), with no need to change source files (I changed the Makefile and some paths, but that's it!). As default this results in a compiler that uses floating point insns, but if you'd rather not, changing 'toplev.c' to define DEFAULT_TARGET from 1 to 0 (this is from memory - I'm not at my minix-box) will handle that too. Don't make the libs, use the old gnulib&libc.a. I have successfully compiled 1.40 with itself, and everything works fine (I got the newest versions of gas and binutils at the same time, as I've heard of bugs with older versions of ld.c). Makefile needs some chmem's (and gcc2minix if you're still using it). Linus Torvalds [email blocked] PS. Could someone please try to finger me from overseas, as I've installed a "changing .plan" (made by your's truly), and I'm not certain it works from outside? It should report a new .plan every time.
First Linux announcement:
From: Linus Benedict Torvalds [email blocked] Newsgroups: comp.os.minix Subject: What would you like to see most in minix? Date: 25 Aug 91 20:57:08 GMT Hello everybody out there using minix - I'm doing a (free) operating system (just a hobby, won't be big and professional like gnu) for 386(486) AT clones. This has been brewing since april, and is starting to get ready. I'd like any feedback on things people like/dislike in minix, as my OS resembles it somewhat (same physical layout of the file-system (due to practical reasons) among other things). I've currently ported bash(1.08) and gcc(1.40), and things seem to work. This implies that I'll get something practical within a few months, and I'd like to know what features most people would want. Any suggestions are welcome, but I won't promise I'll implement them :-) Linus (torva... at kruuna.helsinki.fi) PS. Yes - it's free of any minix code, and it has a multi-threaded fs. It is NOT protable (uses 386 task switching etc), and it probably never will support anything other than AT-harddisks, as that's all I have :-(. From: Jyrki Kuoppala [email blocked] Newsgroups: comp.os.minix Subject: What would you like to see most in minix? Date: 25 Aug 91 23:44:50 GMT In article Linus Benedict Torvalds writes: >I've currently ported bash(1.08) and gcc(1.40), and things seem to work. >This implies that I'll get something practical within a few months, and >I'd like to know what features most people would want. Any suggestions >are welcome, but I won't promise I'll implement them :-) Tell us more! Does it need a MMU? >PS. Yes - it's free of any minix code, and it has a multi-threaded fs. >It is NOT protable (uses 386 task switching etc) How much of it is in C? What difficulties will there be in porting? Nobody will believe you about non-portability ;-), and I for one would like to port it to my Amiga (Mach needs a MMU and Minix is not free). As for the features; well, pseudo ttys, BSD sockets, user-mode filesystems (so I can say cat /dev/tcp/kruuna.helsinki.fi/finger), window size in the tty structure, system calls capable of supporting POSIX.1. Oh, and bsd-style long file names. //Jyrki From: Linus Benedict Torvalds [email blocked] Newsgroups: comp.os.minix Subject: Re: What would you like to see most in minix? Date: 26 Aug 91 11:06:02 GMT In article Jyrki Kuoppala writes: >> [re: my post about my new OS] >Tell us more! Does it need a MMU? Yes, it needs a MMU (sorry everybody), and it specifically needs a 386/486 MMU (see later). >>PS. Yes - it's free of any minix code, and it has a multi-threaded fs. >>It is NOT protable (uses 386 task switching etc) >How much of it is in C? What difficulties will there be in porting? >Nobody will believe you about non-portability ;-), and I for one would >like to port it to my Amiga (Mach needs a MMU and Minix is not free). Simply, I'd say that porting is impossible. It's mostly in C, but most people wouldn't call what I write C. It uses every conceivable feature of the 386 I could find, as it was also a project to teach me about the 386. As already mentioned, it uses a MMU, for both paging (not to disk yet) and segmentation. It's the segmentation that makes it REALLY 386 dependent (every task has a 64Mb segment for code & data - max 64 tasks in 4Gb. Anybody who needs more than 64Mb/task - tough cookies). It also uses every feature of gcc I could find, specifically the __asm__ directive, so that I wouldn't need so much assembly language objects. Some of my "C"-files (specifically mm.c) are almost as much assembler as C. It would be "interesting" even to port it to another compiler (though why anybody would want to use anything other than gcc is a mystery). Unlike minix, I also happen to LIKE interrupts, so interrupts are handled without trying to hide the reason behind them (I especially like my hard-disk-driver. Anybody else make interrupts drive a state- machine?). All in all it's a porters nightmare. >As for the features; well, pseudo ttys, BSD sockets, user-mode >filesystems (so I can say cat /dev/tcp/kruuna.helsinki.fi/finger), >window size in the tty structure, system calls capable of supporting >POSIX.1. Oh, and bsd-style long file names. Most of these seem possible (the tty structure already has stubs for window size), except maybe for the user-mode filesystems. As to POSIX, I'd be delighted to have it, but posix wants money for their papers, so that's not currently an option. In any case these are things that won't be supported for some time yet (first I'll make it a simple minix- lookalike, keyword SIMPLE). Linus [email blocked] PS. To make things really clear - yes I can run gcc on it, and bash, and most of the gnu [bin/file]utilities, but it's not very debugged, and the library is really minimal. It doesn't even support floppy-disks yet. It won't be ready for distribution for a couple of months. Even then it probably won't be able to do much more than minix, and much less in some respects. It will be free though (probably under gnu-license or similar). From: Alan Barclay [email blocked] Newsgroups: comp.os.minix Subject: Re: What would you like to see most in minix? Date: 27 Aug 91 14:34:32 GMT In article Linus Benedict Torvalds writes: >yet) and segmentation. It's the segmentation that makes it REALLY 386 >dependent (every task has a 64Mb segment for code & data - max 64 tasks >in 4Gb. Anybody who needs more than 64Mb/task - tough cookies). Is that max 64 64Mb tasks or max 64 tasks no matter what their size? -- Alan Barclay iT | E-mail : [email blocked] Barker Lane | BANG-STYLE : [email blocked] CHESTERFIELD S40 1DY | VOICE : +44 246 214241 From: Linus Benedict Torvalds [email blocked] Newsgroups: comp.os.minix Subject: Re: What would you like to see most in minix? Date: 28 Aug 91 10:56:19 GMT In article Alan Barclay writes: >In article Linus Benedict Torvalds writes: >>yet) and segmentation. It's the segmentation that makes it REALLY 386 >>dependent (every task has a 64Mb segment for code & data - max 64 tasks >>in 4Gb. Anybody who needs more than 64Mb/task - tough cookies). >Is that max 64 64Mb tasks or max 64 tasks no matter what their size? I'm afraid that is 64 tasks max (and one is used as swapper), no matter how small they should be. Fragmentation is evil - this is how it was handled. As the current opinion seems to be that 64 Mb is more than enough, but 64 tasks might be a little crowded, I'll probably change the limits be easily changed (to 32Mb/128 tasks for example) with just a recompilation of the kernel. I don't want to be on the machine when someone is spawning >64 processes, though :-) Linus
Early Linux installation guide:
Installing Linux on your system Ok, this is a short guide for those people who actually want to get a running system, not just look at the pretty source code :-). You'll certainly need minix for most of the steps. 0. Back up any important software. This kernel has been working beautifully on my machine for some time, and has never destroyed anything on my hard-disk, but you never can be too careful when it comes to using the disk directly. I'd hate to get flames like "you destroyed my entire collection of Sam Fox nude gifs (all 103 of them), I'll hate you forever", just because I may have done something wrong. Double-check your hardware. If you are using other than EGA/VGA, you'll have to make the appropriate changes to 'linux/kernel/console.c', which may not be easy. If you are able to use the at_wini.c under minix, linux will probably also like your drive. If you feel comfortable with scan-codes, you might want to hack 'linux/kernel/keyboard.s' making it more practical for your [US|German|...] keyboard. 1. Decide on what root device you'll be using. You can use any (standard) partition on any of your harddisks, the numbering is the same as for minix (ie 0x306, which I'm using, means partition 1 on hd2). It is certainly possible to use the same device as for minix, but I wouldn't recommend it. You'd have to change pathnames (or make a chroot in init) to get minix and linux to live together peacefully. I'd recommend making a new filesystem, and filling it with the necessary files: You need at least the following: - /dev/tty0 (same as under minix, ie mknod ...) - /dev/tty (same as under minix) - /bin/sh (link to bash) - /bin/update (I guess this should be /etc/update ...) Note that linux and minix binaries aren't compatible, although they use the same (gcc-)header (for ease of cross-compiling), so running one under the other will result in errors. 2. Compile the source, making necessary changes into the makefiles and linux/include/linux/config.h and linux/boot/boot.s. I'm using a slightly hacked gcc-1.40, to which I have added a -mstring-insns flag, which uses the i386 string instructions for structure copy etc. Removing the flag from all makefiles should do the trick for you. NOTE! I'm using -Wall, and I'm not seeing many warnings (2 I think, one about _exit returning although it's volatile - it's ok.) If you get more warnings when compiling, something's wrong. 3. Copy the resultant code to a diskette of the right type. Use 'cp Image /dev/PS0' or equivalent. 4. Boot with the new diskette. If you've done everything right (and if *I've* done everything right), you should now be running bash as root. You can't do much (alias ls='echo *' is a good idea :-), but if you do run, most other things should work. I'd be happy to hear from anybody that has come this far - and I'll send any ported binaries you might want (and I have). I'll also put them out for ftp if there is enough interest. With gcc, make and uemacs, I've been able to stop crosscompiling and actually compile natively under linux. (I also have a term-emu, sz/rz, sed, etc ...) The boot-sequence should start with "Loading system...", and then a "Partition table ok" followed by some root-dev info. If you forget to make the /dev/tty0-character device, you'll never see anything but the "loading" message. Hopefully errors will be told to the console, but if there are problems at boot-up there is a distinct possibility that the machine just hangs. 5. Check the new filesystem regularly with (minix) fsck. I haven't got any errors for some time now, but I cannot guarantee that this means it will never happen. Due to slight differences in 'unlink', fsck will report "mode inode XXX not cleared", but that isn't an error, and you can safely ignore it (if you don't like it, do a fsck -a every once in a while). Minix "restore" will not work on a file deleted with linux - so be extra careful if you have a tendency to delete files you don't really want to. Logging out from the "login-shell" will automatically do a sync, and will leave you hanging without any processes (except update, which isn't much fun), so do the "three-finger-salute" to restart dos/minix/linux or whatever. 6. Mail me and ask about problems/updates etc. Even more welcome are success-reports (yeah, sure), and bugreports or even patches (or pointers to corrections). NOTE!!! I haven't included diffs with the binaries I've posted for the simple reason that there aren't any - I've had this silly idea that I'd rather change the OS than do a lot of porting. All source to the binaries can be found on nic.funet.fi under /pub/gnu or /pub/unix. Changes have been to makefiles or configuration files, and anybody interested in them might want to contact me. Mostly it's been a matter of adding a -DUSG to makefiles. The one exception if gcc - I've made some hacks on it (string-insns), and have got it (with the gracious help of Bruce Evans) to correctly emit software floating point. I haven't got diffs to that one either, as my hard-disk is overflowing and I cannot accomodate both originals and changes, but as per the GNU copyleft I'll make them available if someone wants them. I hope nobody want's them :-) Linus [email blocked]
README about early pictures of Linus Torvalds:
I finally got these made, and even managed to persuade Linus into allowing me to publish three pictures instead of only the first one. (He still vetoes the one with the toy moose... :-) linus1.gif, linus2.gif, linus3.gif Three pictures of Linus Torvalds, showing what a despicable figure he is in real life. The beer is from the pre-Linux era, so it's not virtual. In nic.funet.fi: pub/OS/Linux/doc/PEOPLE. -- Lars.Wirzenius [email blocked] (finger wirzeniu at klaava.helsinki.fi) MS-DOS, you can't live with it, you can live without it.
