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> Most distros symlink /bin to /usr/bin. Uhm, no? I've only seen it in recent CentOS (older versions didn't have it), and maybe Fedora does this as well. > I

by dozzie 11y ago

> Most distros symlink /bin to /usr/bin. Uhm, no? I've only seen it in recent CentOS (older versions didn't have it), and maybe Fedora does this as well. > I think the question is asking you to use /lib/ld.so, but it's a bit of a weird question to ask. Not really. You can do it in any number of ways, including using Perl/Python/Ruby, writing a short C program, or overwriting another file with execution permissions. My favourite way is a surprise to most people only because they don't know how ELF binaries work.

cyphar 11y ago
> Most distros symlink /bin to /usr/bin. > > Uhm, no? I've only seen it in recent CentOS (older versions didn't have it), and maybe Fedora does this as well. Arch, Ubuntu, Debian all do it. > Not really. You can do it in any number of ways, including using Perl/Python/Ruby, writing a short C program, or overwriting another file with execution permissions. Only the last one is a clever solution. "Just write a program" isn't a fun answer. :P > My favourite way is a surprise to most people only because they don't know how ELF binaries work. What do you mean? They didn't know there's a copy of the same binary?
- dozzie 11y ago
  >>> Most distros symlink /bin to /usr/bin. >> Uhm, no? I've only seen it in recent CentOS (older versions didn't have it), and maybe Fedora does this as well. > Arch, Ubuntu, Debian all do it. I haven't checked Arch, but neither Ubuntu 16.04 nor Debian Jessie haven't created /bin as a symlink. >> You can do it [restoring execution bit on /bin/chmod] in any number of ways [...] > Only the last one is a clever solution On interview you don't need to have the most clever answer. It's better to show you understand the mechanisms underneath by having several sensible ways. > What do you mean? They didn't know there's a copy of the same binary? No, I meant this: https://news.ycombinator.com/item?id=11627670 https://news.ycombinator.com/item?id=11627670 And there is no copy of the same binary.
  - cyphar 11y ago
    > I haven't checked Arch, but neither Ubuntu 16.04 nor Debian Jessie haven't created /bin as a symlink. Odd, I could've sworn they did. I stand corrected. > > What do you mean? They didn't know there's a copy of the same binary? > No, I meant this: https://news.ycombinator.com/item?id=11627670 https://news.ycombinator.com/item?id=11627670 > And there is no copy of the same binary. That's what I said, you use the ELF interpreter. :P

by dozzie 11y ago

cyphar 11y ago

> Most distros symlink /bin to /usr/bin. > > Uhm, no? I've only seen it in recent CentOS (older versions didn't have it), and maybe Fedora does this as well. Arch, Ubuntu, Debian all do it. > Not really. You can do it in any number of ways, including using Perl/Python/Ruby, writing a short C program, or overwriting another file with execution permissions. Only the last one is a clever solution. "Just write a program" isn't a fun answer. :P > My favourite way is a surprise to most people only because they don't know how ELF binaries work. What do you mean? They didn't know there's a copy of the same binary?

dozzie 11y ago
>>> Most distros symlink /bin to /usr/bin. >> Uhm, no? I've only seen it in recent CentOS (older versions didn't have it), and maybe Fedora does this as well. > Arch, Ubuntu, Debian all do it. I haven't checked Arch, but neither Ubuntu 16.04 nor Debian Jessie haven't created /bin as a symlink. >> You can do it [restoring execution bit on /bin/chmod] in any number of ways [...] > Only the last one is a clever solution On interview you don't need to have the most clever answer. It's better to show you understand the mechanisms underneath by having several sensible ways. > What do you mean? They didn't know there's a copy of the same binary? No, I meant this: https://news.ycombinator.com/item?id=11627670 https://news.ycombinator.com/item?id=11627670 And there is no copy of the same binary.
- cyphar 11y ago
  > I haven't checked Arch, but neither Ubuntu 16.04 nor Debian Jessie haven't created /bin as a symlink. Odd, I could've sworn they did. I stand corrected. > > What do you mean? They didn't know there's a copy of the same binary? > No, I meant this: https://news.ycombinator.com/item?id=11627670 https://news.ycombinator.com/item?id=11627670 > And there is no copy of the same binary. That's what I said, you use the ELF interpreter. :P