:(){:|:&};:
在Linux系统下执行这段代码 :(){ :|:& }；： 就会引起死机，一旦执行起来后，唯一的方法就是重启系统。实际上这段代码是一段无限递归代码，将系统资源耗尽。 在Linux系统下执行这段代码 :(){ :|:& }；： 就会引起死机，一旦执行起来后，唯一的方法就是重启系统。实际上这段代码是一段无限递归代码，将系统资源耗尽。
本文下面有这段代码的详细解释，为了防止fork炸弹，方法就是限制用户能够启动的进程数。具体做法，编辑/etc/security/limits.conf文件，在末尾加入 ：
* hard nproc 200
将用户的进程数限制为200，经过测试，root账户不受这个限制。
Q. Can you explain following bash code or bash fork() bomb?
:(){ :|:& };:
A. This is a bash function. It gets called recursively (recursivefunction). This is most horrible code for any Unix / Linux box. It isoften used by sys admin to test user processes limitations (Linuxprocess limits can be configured via /etc/security/limits.conf and PAM).
Once a successful fork bomb has been activated in a system it may notbe possible to resume normal operation without rebooting, as the onlysolution to a fork bomb is to destroy all instances of it.
WARNING! These examples may crash your computer if executed.
Understanding :(){ :|:& };: fork() bomb code
:() - It is a function name. It accepts no arguments at all. Generally, bash function is defined as follows:
foo(){
arg1=$1
echo ''
#do_something on $arg argument
}
fork() bomb is defined as follows:
:(){
:|:&
};:
:|: - Next it call itself using programming technique called recursionand pipes the output to another call of the function ':'. The worstpart is function get called two times to bomb your system.
& - Puts the function call in the background so child cannot die at all and start eating system resources.
; - Terminate the function definition
: - Call (run) the function aka set the fork() bomb.
Here is more human readable code:
bomb() {
bomb | bomb &
}; bomb
Properly configured Linux / UNIX box should not go down when fork() bomb sets off.