Windows questions are NOT on topic here.

Now that's out of the way, lets discuss damage done by a Linux distribution's installer.

There are two topics I regularly see:

  • (how to roll back) how to reverse damage done by a linux installer. (the answer could be about what the installer does and therefore how to undo it) In particular discussion Legacy boot sector and UEFI entries along with a mention of BIOS being able to select between UEFI entries.
  • (how to fix forward) how to persuade grub or other boot loaders to find windows (where nix boot loaders could be considered on topic).

One of the biggest arguments for having stock answers to this on unix.stackexchange.com is "if not here then where". Most Windows questions we would still bounce to Superuser.com. But given the damage has usually been done by a Linux installer, it feels inappropriate to expect Window's experts to know what a linux installer has done. That knowledge is more likely to be found here.

Marking a question as duplicate is much more helpful than simply downvoting and closing. It's also a lot less unfriendly which is a common discussion point of stackexchange at the moment.

So a few stock answers for questions like this might be useful: Can't boot to windows after installing Ubuntu in UEFI

These questions typically have too little information to answer categorically. That's frequently because people who need to ask already know too little to include the right information. These are typically newby questions.

However when you consider the questions I believe it should simple enough to come up with a "blind" checklist of things to try.

Find out legacy or EFI then try:

If legacy then try:

  • this
  • this

If EFI then try

  • this
  • this
  • this

If all this fails then this is a windows question so try searching on Superuser.com

It takes some grace to apply this well. I note some users are averse to re-framing another OP's question in order to bring it on topic, even where the meaning is not changed. The question I reference above is framed as a Windows question, but could arguably be described as matching either "how to reverse out grub" or "how to fix grub". My own view is that we should look at the inference of the question rather than playing buzzword bingo to determine whether it is on or off topic.

  • 1
    Great topic! "...damage done by a Linux distribution's installer." Cut's to the heart of the matter. Have an upvote! :)
    – 0xSheepdog
    Apr 4 '19 at 15:57
  • 1
    Do you have any more suggested posts that deal well with these issues, which could be used as the 'default' (probably not), or used to inform a new question and response which could become the 'default'?
    – 0xSheepdog
    Apr 4 '19 at 16:04
  • 1
    Alas a lot of these are hard to find since many people have interpreted them as windows (only) questions and closed them. Apr 5 '19 at 13:28
  • Would you expect a Windows expert to be able to tell you how to reinstall a Linux bootloader, because you overwrote it with a Windows one? If so, why? If not, why is your proposal any better? Also, a thought experiment: if you overwrote a Windows bootloader with grub, then overwrote grub with zeros and then you want to reinstall the Windows bootloader, is it still a "unix question"?
    – user41515
    Apr 11 '19 at 23:49
  • @Wumpus there you have assumed legacy boot. This topic or rather more nuanced with the introduction of EFI. But yes discussing what is done by dd if=/dev/zero of=/dev/sda is clearly a Unix question! Apr 12 '19 at 7:22
  • If "what is done" is "you have a clean slate; all operating systems are equally non-bootable" why is it OK to expect Unix people to have the answers for making non-Unix operating systems boot?
    – user41515
    Apr 12 '19 at 23:31
  • It's reasonable to expect linux users to understand how an installer works and understand the damage it might do. The fact that the damage is irreversible is in point of fact specialist Linux knowledge. Indeed with EFI it regularly isn't irriversable and the question requires no windows knowledge to answer. In the case of legacy boot It's perfectly legitimate for Linux users to answer with "here's a description of the damage that was done ... Here's the question(s) you should seek answers to next, they should be directed to windows experts". Apr 13 '19 at 6:21

Indeed, if there's an issue that comes up often, it's good to have a reference question with a detailed answer that handles the topic in a didactic and generic way. On Stack Exchange we usually call those canonical questions.

By all means, if the issue warrants it, you know the topic well, and there isn't already a usable question on the topic, please write a question and an answer. A few tips:

  • It's generally better to ask a new question than to repurpose an existing one. Actual questions asked by someone facing the problem often have a lot of additional details that distract from the main topic.
  • A canonical question should have a detailed answer that addresses all the common concerns, provides solutions, and includes links for more information.
  • A canonical question is useful duplicate target when people ask specifically about that particular issue. But in many cases, it takes a bit of analysis to relate the specific question to the issue, or a bit of extra work is needed to fix the problem. In such cases, write a short answer and link to the canonical question for the detailed explanation.
  • Link the question from the relevant tag wiki(s). That's the easiest way to find it.

Here are a few canonical questions that I wrote and which I think are good examples of what a canonical question should be:

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