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Comment by knodi123 | Hacker News Reader

As a linux neophyte, I once struggled to remember whether the trailing slash on a directory was important. So I typed "rm -rf", and pasted the directory name "schoolwork/project1 " (with a trailing space), but then I waffled and decided to add a trailing slash. So I changed it to "rm -rf schoolwork/project1 /".

That's my theory as to what they did.

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  rm -Rf test /
  rm: it is dangerous to operate recursively on ‘/’
  rm: use --no-preserve-root to override this failsafe

GNU rm, but I don't know when it was introduced.

Quick googling around, and it seems like this behavior (in Ubuntu) changed somewhere near the end of 2008: https://bugs.launchpad.net/ubuntu/+source/coreutils/+bug/174...

tl;dr That's when coreutils Ubuntu package switched from "--no-preserve-root" to "--preserve-root" by default.

This is relatively recent, and caused quite a stir when it was introduced. Certainly not around during Toy Story 2.

edit: More info:

https://lwn.net/Articles/327141/

One feature I've always wanted is to make a directory non-deletable without otherwise changing the directory's functionality. So if I do "rm -rf ~/work" I don't lose anything, but I can still do "touch ~/work/whatever". As far as I know, this is impossible.

You don't actually need write access to a file/directory to delete it. You only need write access to the parent (removing or adding a file modifies the container, not the contained).

Remove write access to the parent directory, while keeping traversal and read rights, and you'll be sorted.

But then I can't add files to my home directory...

You said it was impossible. I simply indicated it wasn't.

The question was perhaps imprecisely phrased, but I think you can figure out what I'm trying to accomplish.

So don't put the stuff you want to protect this way in your home directory, but somewhere else, and symlink the relevant directories to your home directory.

Quite clumsy, but I guess it works. I'll keep it in mind, thanks for the idea.

# mkdir /tmp/foo

# touch /tmp/foo/.immutable

# chattr +i /tmp/foo/.immutable

# rm -rf /tmp/foo

It's not EXACTLY what you asked for, but the .immutable file cannot be deleted until you call chattr -i on it, which protects the directory....

That doesn't protect siblings of <foo/.immutable>...

If I remember correctly, they were using Solaris at the time, and I know for sure that Solaris did not have this safety net, nor did Linux at the time. The requirement of --no-preserve-root was introduced almost a decade later.

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