首先重启进入GRUB，编辑内核命令行：Ubuntu/Debian添加"rw init=/bin/bash"，CentOS/RHEL添加"rd.break"，启动后挂载文件系统为读写模式，执行passwd修改root密码，最后重启生效。If you forget the Linux root password, reboot and enter GRUB. Edit the kernel line: for Ubuntu/Debian, add "rw init=/bin/bash"; for CentOS/RHEL, add "rd.break".
Boot into single-user mode, mount the filesystem as read-write, use `passwd` to reset the root password, and reboot.
