Why can't I crash my system with a fork bomb?

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2
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Recently I've been digging informations about processes in GNU/Linux and I met the infamous fork bomb :



: : ; :


Theorically, it is supposed to duplicate itself infinitely until the system runs out of ressources...



However, I've tried testing both on a CLI Debian and a GUI Mint distro, it doesn't seem to impact much the system. Yes there are tons of processes that are created, and after a while I read in console messages like :




bash: fork: Ressource temporarily unavailable



bash: fork: retry: No child processes




But after some time all the processes just get killed and everything goes back to normal. I've read that the ulimit set a maximum amount of process per user but I can't seem to be able to raise it really far.



So my question is : what are the system protections against a fork-bomb ? Why doesn't it replicate itself until everything freezes or at least lags a lot ? Is there a way to really crash a system with a fork bomb ?






linux process fork ulimit







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  • What's your max PID currently set to?
    – dsstorefile1
    2 hours ago










  • The fork bomb code as posted here is incorrect by the way. It results in syntax error. But it may be better to leave it incorrect.
    – Hkoof
    26 mins ago














up vote
2
down vote

favorite












Recently I've been digging informations about processes in GNU/Linux and I met the infamous fork bomb :



: : ; :


Theorically, it is supposed to duplicate itself infinitely until the system runs out of ressources...



However, I've tried testing both on a CLI Debian and a GUI Mint distro, it doesn't seem to impact much the system. Yes there are tons of processes that are created, and after a while I read in console messages like :




bash: fork: Ressource temporarily unavailable



bash: fork: retry: No child processes




But after some time all the processes just get killed and everything goes back to normal. I've read that the ulimit set a maximum amount of process per user but I can't seem to be able to raise it really far.



So my question is : what are the system protections against a fork-bomb ? Why doesn't it replicate itself until everything freezes or at least lags a lot ? Is there a way to really crash a system with a fork bomb ?






linux process fork ulimit







share|improve this question





















  • What's your max PID currently set to?
    – dsstorefile1
    2 hours ago










  • The fork bomb code as posted here is incorrect by the way. It results in syntax error. But it may be better to leave it incorrect.
    – Hkoof
    26 mins ago












up vote
2
down vote

favorite









up vote
2
down vote

favorite











Recently I've been digging informations about processes in GNU/Linux and I met the infamous fork bomb :



: : ; :


Theorically, it is supposed to duplicate itself infinitely until the system runs out of ressources...



However, I've tried testing both on a CLI Debian and a GUI Mint distro, it doesn't seem to impact much the system. Yes there are tons of processes that are created, and after a while I read in console messages like :




bash: fork: Ressource temporarily unavailable



bash: fork: retry: No child processes




But after some time all the processes just get killed and everything goes back to normal. I've read that the ulimit set a maximum amount of process per user but I can't seem to be able to raise it really far.



So my question is : what are the system protections against a fork-bomb ? Why doesn't it replicate itself until everything freezes or at least lags a lot ? Is there a way to really crash a system with a fork bomb ?






linux process fork ulimit







share|improve this question













Recently I've been digging informations about processes in GNU/Linux and I met the infamous fork bomb :



: : ; :


Theorically, it is supposed to duplicate itself infinitely until the system runs out of ressources...



However, I've tried testing both on a CLI Debian and a GUI Mint distro, it doesn't seem to impact much the system. Yes there are tons of processes that are created, and after a while I read in console messages like :




bash: fork: Ressource temporarily unavailable



bash: fork: retry: No child processes




But after some time all the processes just get killed and everything goes back to normal. I've read that the ulimit set a maximum amount of process per user but I can't seem to be able to raise it really far.



So my question is : what are the system protections against a fork-bomb ? Why doesn't it replicate itself until everything freezes or at least lags a lot ? Is there a way to really crash a system with a fork bomb ?






linux process fork ulimit




linux process fork ulimit






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asked 2 hours ago









Plancton

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  • What's your max PID currently set to?
    – dsstorefile1
    2 hours ago










  • The fork bomb code as posted here is incorrect by the way. It results in syntax error. But it may be better to leave it incorrect.
    – Hkoof
    26 mins ago
















  • What's your max PID currently set to?
    – dsstorefile1
    2 hours ago










  • The fork bomb code as posted here is incorrect by the way. It results in syntax error. But it may be better to leave it incorrect.
    – Hkoof
    26 mins ago















What's your max PID currently set to?
– dsstorefile1
2 hours ago




What's your max PID currently set to?
– dsstorefile1
2 hours ago












The fork bomb code as posted here is incorrect by the way. It results in syntax error. But it may be better to leave it incorrect.
– Hkoof
26 mins ago




The fork bomb code as posted here is incorrect by the way. It results in syntax error. But it may be better to leave it incorrect.
– Hkoof
26 mins ago










1 Answer
1






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3
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You probably have a Linux distro that uses systemd.



Systemd creates a cgroup for each user, and all processes of a user belong to the same cgroup.



Cgroups is a Linux mechanism to set limits on system resources like max number of processes, CPU cycles, RAM usage, etc. This is a different, more modern, layer of resource limiting than ulimit (which uses the getrlimit() syscall).



To change the max number of processes system will allow for each user, edit /etc/systemd/logind.conf. The default is max 12288 processes per user.



More info about this:



  • man 5 systemd.slice

  • man 5 logind.conf


  • http://0pointer.de/blog/projects/systemd.html (search this page for cgroups)

  • man 7 cgroups

  • https://en.wikipedia.org/wiki/Cgroups





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    up vote
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    down vote













    You probably have a Linux distro that uses systemd.



    Systemd creates a cgroup for each user, and all processes of a user belong to the same cgroup.



    Cgroups is a Linux mechanism to set limits on system resources like max number of processes, CPU cycles, RAM usage, etc. This is a different, more modern, layer of resource limiting than ulimit (which uses the getrlimit() syscall).



    To change the max number of processes system will allow for each user, edit /etc/systemd/logind.conf. The default is max 12288 processes per user.



    More info about this:



    • man 5 systemd.slice

    • man 5 logind.conf


    • http://0pointer.de/blog/projects/systemd.html (search this page for cgroups)

    • man 7 cgroups

    • https://en.wikipedia.org/wiki/Cgroups





    share|improve this answer
























      up vote
      3
      down vote













      You probably have a Linux distro that uses systemd.



      Systemd creates a cgroup for each user, and all processes of a user belong to the same cgroup.



      Cgroups is a Linux mechanism to set limits on system resources like max number of processes, CPU cycles, RAM usage, etc. This is a different, more modern, layer of resource limiting than ulimit (which uses the getrlimit() syscall).



      To change the max number of processes system will allow for each user, edit /etc/systemd/logind.conf. The default is max 12288 processes per user.



      More info about this:



      • man 5 systemd.slice

      • man 5 logind.conf


      • http://0pointer.de/blog/projects/systemd.html (search this page for cgroups)

      • man 7 cgroups

      • https://en.wikipedia.org/wiki/Cgroups





      share|improve this answer






















        up vote
        3
        down vote










        up vote
        3
        down vote









        You probably have a Linux distro that uses systemd.



        Systemd creates a cgroup for each user, and all processes of a user belong to the same cgroup.



        Cgroups is a Linux mechanism to set limits on system resources like max number of processes, CPU cycles, RAM usage, etc. This is a different, more modern, layer of resource limiting than ulimit (which uses the getrlimit() syscall).



        To change the max number of processes system will allow for each user, edit /etc/systemd/logind.conf. The default is max 12288 processes per user.



        More info about this:



        • man 5 systemd.slice

        • man 5 logind.conf


        • http://0pointer.de/blog/projects/systemd.html (search this page for cgroups)

        • man 7 cgroups

        • https://en.wikipedia.org/wiki/Cgroups





        share|improve this answer












        You probably have a Linux distro that uses systemd.



        Systemd creates a cgroup for each user, and all processes of a user belong to the same cgroup.



        Cgroups is a Linux mechanism to set limits on system resources like max number of processes, CPU cycles, RAM usage, etc. This is a different, more modern, layer of resource limiting than ulimit (which uses the getrlimit() syscall).



        To change the max number of processes system will allow for each user, edit /etc/systemd/logind.conf. The default is max 12288 processes per user.



        More info about this:



        • man 5 systemd.slice

        • man 5 logind.conf


        • http://0pointer.de/blog/projects/systemd.html (search this page for cgroups)

        • man 7 cgroups

        • https://en.wikipedia.org/wiki/Cgroups






        share|improve this answer












        share|improve this answer



        share|improve this answer










        answered 1 hour ago









        Hkoof

        1843




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