>> When this code was written, uuidgen was Essential: yes and so was available >> on every Debian system, so the second method was never used.
Makes sense, but the fallback code has come to life. > Which kernel version provides /proc/sys/kernel/random/uuid ? It predates the start of the git era in 2.6.12-rc2, and a quick search of earlier history shows it was in 2.3.16, and was not in 2.3.15pre3. http://repo.or.cz/davej-history.git/blob/0d447745e5268dca6201eaa095a28cc79bd28be0:/drivers/char/random.c http://repo.or.cz/davej-history.git/blob/9ec0c4e2f8eff2496373ebbd1010aa8484b59495:/drivers/char/random.c The 2.3.16 file is dated 30 August 1999. > What about kfreebsd ? FreeBSD appears to use a uuidgen(2) system call rather than a /proc file: https://www.freebsd.org/cgi/man.cgi?query=uuidgen&sektion=2 ... however, that uses the clock+MAC form https://github.com/freebsd/freebsd/blob/386ddae58459341ec567604707805814a2128a57/sys/kern/kern_uuid.c
