一天一个 Linux 命令（32）：umount命令

umount [-hV]
umount -a [options]
umount [options] <source> | <directory>
umount [参数] [文件系统]


Usage:
 umount [-hV]
 umount -a [options]
 umount [options] <source> | <directory>

Options:
 -a, --all               unmount all filesystems
 -A, --all-targets       unmount all mountpoins for the given device
                         in the current namespace
 -c, --no-canonicalize   don't canonicalize paths
 -d, --detach-loop       if mounted loop device, also free this loop device
     --fake              dry run; skip the umount(2) syscall
 -f, --force             force unmount (in case of an unreachable NFS system)
 -i, --internal-only     don't call the umount.<type> helpers
 -n, --no-mtab           don't write to /etc/mtab
 -l, --lazy              detach the filesystem now, and cleanup all later
 -O, --test-opts <list>  limit the set of filesystems (use with -a)
 -R, --recursive         recursively unmount a target with all its children
 -r, --read-only         In case unmounting fails, try to remount read-only
 -t, --types <list>      limit the set of filesystem types
 -v, --verbose           say what is being done

 -h, --help     display this help and exit
 -V, --version  output version information and exit

-a	卸载/etc/mtab中记录的所有文件系统
-f  强制卸载(比如在无法访问NFS系统的情况下)
-h	显示帮助
-n	卸载时不要将信息存入/etc/mtab文件中
-l  分离文件系统，稍后进行清除
-r	若无法成功卸载，则尝试以只读的方式重新挂入文件系统
-t	文件系统类型：仅卸载选项中所指定的文件系统
-v	执行时显示详细的信息
-V	显示版本信息

#通过设备名卸载  
# umount -v /dev/vda1
/dev/vda1 umounted  

#通过挂载点卸载
# umount -v /data     
/data umounted

#如果设备正忙，卸载即告失败。卸载失败的常见原因是，某个打开的shell当前目录为挂载点里的某个目录
#umount -v /data 
#umount: /data: device is busy  

#当有别的程序正在访问挂载的文件时，也会提示卸载失败，通过 lsof  /data  查看是哪个进程占用了/data,使用kill -9 $pid,然后再卸载

#umount -l /data

umount -lf /data