lsof -i:port

根据监听端口号找进程PID

COMMAND   PID USER   FD   TYPE    DEVICE SIZE/OFF NODE NAME
node    14374 root   12u  IPv6 376449654      0t0  TCP *:8957 (LISTEN)

lsof |grep deleted

如果一个文件正在被一个运行中的进程读取，此时删除次文件，此文件空间不会被释放，使用du -sh无法统计此文件占用的空间；可以通过此命令查看已经被删除过仍然占用空间的文件清单，然后通过kill进程释放文件占用空间

Determine which MySQL configuration file is being used

$ which mysqld
/usr/sbin/mysqld

$ /usr/sbin/mysqld --verbose --help | grep -A 1 "Default options"
Default options are read from the following files in the given order:
/etc/mysql/my.cnf ~/.my.cnf /usr/etc/my.cnf

test nginx configuration

nginx -t

docker command

lsns -t net|pid
ls -la /proc/{pid}/ns