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I read the mknod man page, which is (as far as I can tell) what you would use to make a character device like /dev/zero, but I don't see how you would get it to yield an infinite stream of zero bits (or another pattern). What is the procedure for creating such character devices?

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They're implemented in the kernel. Look at zero_lseek, read_zero, write_zero, mmap_zero in drivers/char/mem.c. – David Schwartz Oct 1 '12 at 7:04
Oh…so I would have to modify the kernel? – Blacklight Shining Oct 1 '12 at 7:07
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Not necessarily, it depends on precisely what you want to do. Most likely, you would at least need to implement a module. – David Schwartz Oct 1 '12 at 7:18
What about /dev/one? – Blacklight Shining Oct 1 '12 at 7:45

2 Answers

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All mknod does is associate a device file with a device driver. There are device drivers that implement interaction with actual devices, and there are device drivers that just react to read-write requests in useful ways. If you want to you can sit down and write a driver that returns the lyrics of the Star Spangeled Banner. But it's a matter of coding, not finding the right arguments for mknod.

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mknod creates the device node, but the VFS detects accesses to the device node and reroutes them to the appropriate driver within the kernel for handling. All device nodes, from /dev/null to /dev/sdX to /dev/ttyXX to /dev/videoX are handled this way.

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