[ NOTE! I didn't write this: I'm too lazy to write README's etc. I just make this available because it might just reduce the number of "how do I compile linux" questions on the net (and to me). I'm not guaranteeing anything in this README: things might have changed with 0.97, making this not completely up-to-date. - Linus ] VERY QUICK AND DIRTY README by Lars Wirzenius This is the README for the Linux kernel sources. It tells a few small things about kernel configuration and other things that can perhaps be useful if you want to compile the kernel from scratch. It leaves out a lot as well, probably because the person who wrote it doesn't understand very much about operating systems. Linus did his best to help, but all problems this causes are my fault. In order to compile this version of the kernel you need GCC 2.2.2 or newer. Some makefile targets require special commands which may not be available on all machines (see below). Normal utilities like ls etc are not explicitly listed, they are assumed to be available on all systems. Kernel sources are usually kept in /usr/src/linux. If you have them elsewhere, you will have to change path names in a few places. Filenames that aren't absolute are supposed to be relative to the toplevel kernel source directory. * Basic configuration 1. Edit Makefile: Check the definitions of macros ROOTDEV, KEYBOARD, MATH_EMULATION, RAMDISK and SVGA_MODE before you run make. They are explained in the Makefile. MATH_EMULATION does not hurt much even if you have an FPU (387 or a 486 with a built in FPU), since Linux uses the FPU if it finds one, even with MATH_EMULATION defined. The kernel will be slightly bigger. It is probably not worth it to recompile the kernel just to get rid of the emulation. 2. Create a symlink: ln -s /usr/src/linux/include/linux /usr/include/linux This is required so that tools/build.c will compile and link (it requires the standard versions of headers instead of the kernel specific headers, as it is a normal application, not kernel code). [ Linus's note: I don't think this is required any more, but it's still default installation procedure, and is needed for things like the mkfs sources anyway ] * Things you may want to get rid of 3. To remove SCSI drivers, do this: - remove kernel/blk_drv/scsi/scsi.a from DRIVERS in the Makefile - remove the commands for the subdirs dependency in kernel/blk_drv/Makefile - add "#undef CONFIG_SCSI" to the end of include/linux/config.h The SCSI drivers take a bit of memory, and also slow the bootup a bit, so you may want to get rid of them if you don't have an SCSI drive. 4. The kernel contains code for the extended filesystem (extfs) and MS-DOS filesystem (dosfs), both of which are in testing phases and are not recommended for real use yet. If you don't want to include these in the kernel, do the following: - remove references to these in the FILESYSTEMS macro in the root Makefile - remove directory names from the SUBDIRS macro in fs/Makefile - remove the corresponding lines in the initialization of file_systems in fs/super.c. 5. To configure more ptys do this: - change NR_PTYS in include/linux/tty.h to the number you want - create the new files in /dev - recompile the kernel * Running make Unless you know what you're doing, don't ever run the makefiles in subdirectories by hand. There is a bit of interaction between the various makefiles, e.g. in the form of inherited macros and the like. The following targets all apply for the makefile at the root of the kernel source tree. "make" or "make all" compiles everything. "make Image" is like "make all", but it doesn't bump the number in .version, which tells how many times this version has been compiled (helps you differentiate between different configurations etc). "make disk" is like "make Image", but it additionally writes out a copy of the boot image to a floppy in your first floppy drive (/dev/fd0; change the filename if you want a different floppy). You need to have a formatted, overwritable floppy in that drive when it is time to do the copy. This requires dd. "make dep" updates all dependencies. This requires sed. It modifies the makefiles directly (the end of them, starting at the ###Dependencies -line at the end). "make clean" will remove all object files and other files created by the compilation. This requires basename. You may wish to redirect compiler error messages to a file so that you can review them later and to ease problem fixing. You can do this with Bash with: make something 2>&1 | tee make.out The tee part is so that you can check what is going on while the compilation runs. If you have GNU emacs and use M-x compile you don't need this, of course. Lars Wirzeniu