linux偶尔遇到gradle 编译时, 发生"Too many open files" 导致编译失败.
网上说了一堆 ulimit的, 不顶用. 以下方法 实测有用.

参考:
https://superuser.com/questions/1200539/cannot-increase-open-file-limit-past-4096-ubuntu

// 操作步骤:

$ sudo gedit /etc/security/limits.conf

// 1> 文件末尾加上这个在末尾:
*                -      nofile          65535


// 2> 创建/etc/systemd/system.conf.d/limits.conf, 并增加内容
sudo mkdir /etc/systemd/system.conf.d
sudo touch /etc/systemd/system.conf.d/limits.conf
sudo vim /etc/systemd/system.conf.d/limits.conf

这放到这个文件去:
[Manager]
DefaultLimitNOFILE=65535


// 3> 最后 
systemctl daemon-reexec

然后重启电脑. 
最后 随便弄一个进程  cat /proc/[pid]/limits 可以看到到"Max open files"变为 65535

$ cat /proc/3212/limits 
Limit                     Soft Limit           Hard Limit           Units     
Max cpu time              unlimited            unlimited            seconds   
Max file size             unlimited            unlimited            bytes     
Max data size             unlimited            unlimited            bytes     
Max stack size            8388608              unlimited            bytes     
Max core file size        0                    unlimited            bytes     
Max resident set          unlimited            unlimited            bytes     
Max processes             192492               192492               processes 
Max open files            65535                65535                files     
Max locked memory         16777216             16777216             bytes     
Max address space         unlimited            unlimited            bytes     
Max file locks            unlimited            unlimited            locks     
Max pending signals       192492               192492               signals   
Max msgqueue size         819200               819200               bytes     
Max nice priority         0                    0                    
Max realtime priority     0                    0                    
Max realtime timeout      unlimited            unlimited            us