This is about the AS/400 which is an IBM mini-computer launched in 1988. It lives on today after several name changes and considerable hardware and software changes. It is still often informally called the AS/400 but this is about the early days when that was still the official name. OS/400 was its operating system and the two were tied to each other.

I read, back in the 1990s, that there was a special system program which if deleted would trigger the O/S to uninstall itself during the next IPL (boot). The idea was that an IBM engineer could delete this program if they detected that the system was unlicensed. I think that I read this in an official, reliable source but I cannot be sure after so long. I have been unable to find confirmation. Certainly, IBM took the licensing issue seriously and I am aware of several serious disputes but not the use of this nuclear option.

Can anyone confirm this as true?

Can anyone confirm it as an urban myth that I fell for?

  • 1
    Don't know about AS/400 but on MS DOS, if you deleted . (dot) from the C: drive, it wiped the entire disk including OS.
    – cup
    Apr 14, 2021 at 15:25
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    @cup That is not true. I was sceptical and tried it on fresh MS-DOS 6.22 install. On root of C: drive, executing "del ." would first of all ask if you are sure, and all it does it deletes non-hidden non-system files, so it only deletes CONFIG.SYS and AUTOEXEC.BAT. All subdirectories such as DOS and important OS files are still present (IO.SYS, MSDOS.SYS and COMMAND.COM) on drive root. Would you specify which version of MS-DOS does wipe entire disk?
    – Justme
    Apr 14, 2021 at 17:11
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    @mannaggia - IBM software was leased. Monthly fee. IIRC. The hardware too of course - that was the subject of an action brought by the US government because IBM refused to sell the hardware. But the software too I'm pretty sure (though wikipedia doesn't mention it).
    – davidbak
    Apr 15, 2021 at 0:59
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    @cup Oh and the root of drive would not have "." and ".." either. They are the names or links for current and previous directory. But it is true that DOS 3 did not protect the command interpreter so it is possible to delete COMMAND.COM, but still, typing "del ." on C: drive root would delete COMMAND.COM and any other files not protected like CONFIG. SYS and AUTOEXEC.BAT. It would not "wipe the entire disk" or cause the whole OS to "disappear". But yes the system is unusable until booted from DOS floppy, in which case command interpreter can be copied back to hard drive.
    – Justme
    Apr 15, 2021 at 8:34
  • 4
    This DOS discussion is interesting but probably deserves its own question as it is completely unrelated to OS/400. Today, the descendant of OS/400 has a hierarchical Unix like file system but at the time of this question, it did not. It was very, very different from DOS.
    – badjohn
    Apr 15, 2021 at 8:51


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