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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?

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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
    Commented 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
    Commented 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
    Commented Apr 15, 2021 at 8:34
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    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
    Commented Apr 15, 2021 at 8:51
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    @paxdiablo Probably so but the question was not about how to destroy the O/S in any manner. There are probably many ways to do that. The question was about a program whose purpose was to trigger a delayed uninstall. One accidental near destruction that I witnessed was someone who thought that taking away all authority for all users for all objects would be a good first step strict security. It rendered the system unable to IPL and it took IBM engineers days to recover the system.
    – badjohn
    Commented Dec 30, 2022 at 11:53

1 Answer 1

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I once had a PTF (program temporary fix) take down the entire system. After a day or so of applying what looked like a simple fix, it triggered an IPL (Initial Program Load). The system got stuck in a loop and wouldn't load from any source. An engineer attended and recovered the System with an IPL type C. It took around 7 hours to recover.

see > IPL Types

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  • Thanks but the question is not about anyway to break tye system or how it might itself but a mythical program whose purpose was to trigger an uninstall.
    – badjohn
    Commented Aug 7, 2023 at 20:53
  • The OS is protected (sitting above the subsystems). I can't see how any program could access that. We IPL to a different bank to install PTFs, once happy (days/weeks later) we apply the PTFs permanently and switch to the other bank. I can't imagine a way for a program to automatically gain access to both OS banks and delete the OS, it requires human intervention and access to the control panel. I'm sure this is why IBM designed the two OS banks (three if we count bank C) to protect from utter disaster.
    – Dach
    Commented Aug 7, 2023 at 22:41
  • If you delete enough licenced programs (GO LICPGM) this will screw things up nicely, programs will not be able to gain access to resources they need. However the basic OS will still be running so this doesn't do 100% what you are looking for. The Admin will IPL to A to recover from this.
    – Dach
    Commented Aug 7, 2023 at 22:53
  • The story is old and the system was much simpler then. Also, as an IBM program, it could potentially do almost anything.
    – badjohn
    Commented Aug 7, 2023 at 23:13
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    I've never personally heard about a program that can do that. I spent 32 years working on IBM mainframes, System 36 / 38 / AS400, iseries. Programmer to System manager. Many long nights sat with IBM engineers listening to their stories.
    – Dach
    Commented Aug 8, 2023 at 2:19

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