12 ms·

Show HN: Oops I deleted my bin/ dir

30 points by jarv 6y ago

jarv 6y ago
Hello HN: This is a a modification to an old side-project that explores what is possible when you are left with a shell and no utilities on a Linux machine.
- Jaruzel 6y ago
  It's not really that educational tbh. I am not a bash guru, nor do I wish to be one, so the second question left me cold with no desire to proceed any further. It's a fun game for those with the skills, but an instructional tool it is not.
  - heavenlyblue 6y ago
    It's an algebra game. Given a set of operations, can you get to state X? Usually requires a lot of searching and/or expertise, however the solutions will break pretty easily depending on which shell you're using, etc. So doesn't really teach you anything aside from iterating over a set of all possible operation combinations.
    - weare138 6y ago
      It's also a variation of the classic tech thought experiment/game 'If you only had X and how would you do Y?'. Like 'If all you had was telnet and had to send an email how would you do it?' or some variation of it, was a common one.
  - jarv 6y ago
    If it helps you can click on 'view solutions' to see correct answers if you are stuck.
  - deleted 6y ago
    [deleted]
cerberusss 6y ago
Great fun! As a non-native speaker, I was confused by the "Print its contents" exercise. I tried things involving /dev/lpr.
- jarv 6y ago
  thanks for the feedback, maybe something like "display its contents" would be clearer.
  - cerberusss 6y ago
    Yeah that sounds clear. Awesome puzzle game, very educational.
KMnO4 6y ago
Very cool! I was a bit confused with the marking criteria. For example, my solution for "list all files on one line" appears to work correctly but is said to be incorrect. shopt -s dotglob; for i in *; do echo -n "$i "; done EDIT: I now see that the correct answer is simply "`echo *`". Despite having a dotfile in the directory, it should not be shown.
- jarv 6y ago
  Ah, that is a bug the dotfile should not be there. Thanks!
  - jarv 6y ago
    So the dotfile is resolved but the solution: shopt -s dotglob; for i in *; do echo -n "$i "; done still isn't valid unfortunately because of the extra space at the end, maybe it should be more forgiving about that.
dexen 6y ago
Very amusing - and brings back memories of when a friend actually did remove the /bin (and IIRC the /lib64) a couple months ago :-) Getting stuck on #/oops_print_file_contents - the command times out. Not sure if I'm missing a better solution or perhaps the server is overloaded The command I tried was (here protected with rot13): zncsvyr sbbone < zl-qvffregngvba.gkg; rpub "${sbbone[@]}" -- A mild irritant is that the usual ^W (delete word to the left) instead closes tab in Firefox. Perhaps this could be prevented...?
- jarv 6y ago
  Thanks! It looks like this is adding leading spaces on every line after the first one. The solutions can be viewed https://oops.cmdchallenge.com/#/oops_print_file_contents https://oops.cmdchallenge.com/#/oops_print_file_contents by clicking on "view solutions" if you want to compare. For the ^W thing I'm not sure if it's possible to avoid it, I'll check it out.
krallja 6y ago
I can’t type a space in this app on Mobile Safari. $ requires several key presses to register.
thesh4d0w 6y ago
Maybe I'm missing something obvious here but on the one that asks you to get the proc's cmdline, how do the examples know it's pid 42? Only way I can see to do this would be to echo /proc/* first to see what PID it is, guess it's 42, then go from there, but that violates the "do it in one command" rule at the beginning.
- Crespyl 6y ago
  I haven't dug into the puzzle very far and it didn't seem to like my experiments, but in bash and zsh `$$` will expand to the shells PID. Edit: Oh, I see what you mean now. I think it's just that you're expected to see that there's only a handful of PIDs in /proc and just try them each.
jitendrac 6y ago
Really fun game, finally finished it.
moon2 6y ago
Really fun, kind of trains you to when the situation happens IRL, whether you're thinking about how to escape a shell or if you really did it by mistake. I love showing this screenshot to people: https://imgur.com/a/ziHqJxB https://imgur.com/a/ziHqJxB. I was having problems trying to create a jailed shell, so I decided to bind mount /bin. That of course was a bad idea. I gave up and rm -rf'd the mountpoint without unmounting it. The screenshot has the serial logs from after that :P. I had a good time enjoying my stupidity.
- ThePowerOfFuet 6y ago
  The top of the image is unreadable due to excessive lossy image compression.
  - yesenadam 6y ago
    After clicking on it I can read it fine.
imtringued 6y ago
I do understand that this is meant to be a challenge but if this ever happened to me I'd just boot the archlinux iso and run pacstrap to reinstall pacman and then just reinstall all packages.

30 points by jarv 6y ago

jarv 6y ago

Hello HN: This is a a modification to an old side-project that explores what is possible when you are left with a shell and no utilities on a Linux machine.

Jaruzel 6y ago
It's not really that educational tbh. I am not a bash guru, nor do I wish to be one, so the second question left me cold with no desire to proceed any further. It's a fun game for those with the skills, but an instructional tool it is not.
- heavenlyblue 6y ago
  It's an algebra game. Given a set of operations, can you get to state X? Usually requires a lot of searching and/or expertise, however the solutions will break pretty easily depending on which shell you're using, etc. So doesn't really teach you anything aside from iterating over a set of all possible operation combinations.
  - weare138 6y ago
    It's also a variation of the classic tech thought experiment/game 'If you only had X and how would you do Y?'. Like 'If all you had was telnet and had to send an email how would you do it?' or some variation of it, was a common one.
- jarv 6y ago
  If it helps you can click on 'view solutions' to see correct answers if you are stuck.
- deleted 6y ago
  [deleted]

cerberusss 6y ago

Great fun! As a non-native speaker, I was confused by the "Print its contents" exercise. I tried things involving /dev/lpr.

jarv 6y ago
thanks for the feedback, maybe something like "display its contents" would be clearer.
- cerberusss 6y ago
  Yeah that sounds clear. Awesome puzzle game, very educational.

KMnO4 6y ago

Very cool! I was a bit confused with the marking criteria. For example, my solution for "list all files on one line" appears to work correctly but is said to be incorrect. shopt -s dotglob; for i in *; do echo -n "$i "; done EDIT: I now see that the correct answer is simply "`echo *`". Despite having a dotfile in the directory, it should not be shown.

jarv 6y ago
Ah, that is a bug the dotfile should not be there. Thanks!
- jarv 6y ago
  So the dotfile is resolved but the solution: shopt -s dotglob; for i in *; do echo -n "$i "; done still isn't valid unfortunately because of the extra space at the end, maybe it should be more forgiving about that.

dexen 6y ago

Very amusing - and brings back memories of when a friend actually did remove the /bin (and IIRC the /lib64) a couple months ago :-) Getting stuck on #/oops_print_file_contents - the command times out. Not sure if I'm missing a better solution or perhaps the server is overloaded The command I tried was (here protected with rot13): zncsvyr sbbone < zl-qvffregngvba.gkg; rpub "${sbbone[@]}" -- A mild irritant is that the usual ^W (delete word to the left) instead closes tab in Firefox. Perhaps this could be prevented...?

jarv 6y ago
Thanks! It looks like this is adding leading spaces on every line after the first one. The solutions can be viewed https://oops.cmdchallenge.com/#/oops_print_file_contents https://oops.cmdchallenge.com/#/oops_print_file_contents by clicking on "view solutions" if you want to compare. For the ^W thing I'm not sure if it's possible to avoid it, I'll check it out.

krallja 6y ago

I can’t type a space in this app on Mobile Safari. $ requires several key presses to register.

thesh4d0w 6y ago

Maybe I'm missing something obvious here but on the one that asks you to get the proc's cmdline, how do the examples know it's pid 42? Only way I can see to do this would be to echo /proc/* first to see what PID it is, guess it's 42, then go from there, but that violates the "do it in one command" rule at the beginning.

Crespyl 6y ago
I haven't dug into the puzzle very far and it didn't seem to like my experiments, but in bash and zsh `$$` will expand to the shells PID. Edit: Oh, I see what you mean now. I think it's just that you're expected to see that there's only a handful of PIDs in /proc and just try them each.

jitendrac 6y ago

Really fun game, finally finished it.

moon2 6y ago

Really fun, kind of trains you to when the situation happens IRL, whether you're thinking about how to escape a shell or if you really did it by mistake. I love showing this screenshot to people: https://imgur.com/a/ziHqJxB https://imgur.com/a/ziHqJxB. I was having problems trying to create a jailed shell, so I decided to bind mount /bin. That of course was a bad idea. I gave up and rm -rf'd the mountpoint without unmounting it. The screenshot has the serial logs from after that :P. I had a good time enjoying my stupidity.

ThePowerOfFuet 6y ago
The top of the image is unreadable due to excessive lossy image compression.
- yesenadam 6y ago
  After clicking on it I can read it fine.

imtringued 6y ago

I do understand that this is meant to be a challenge but if this ever happened to me I'd just boot the archlinux iso and run pacstrap to reinstall pacman and then just reinstall all packages.