[root@webnoid hdd]# df -kh
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/centos-root 155G 132G 24G 86% /
devtmpfs 2.8G 0 2.8G 0% /dev
tmpfs 2.8G 8.0K 2.8G 1% /dev/shm
tmpfs 2.8G 259M 2.6G 10% /run
tmpfs 2.8G 0 2.8G 0% /sys/fs/cgroup
/dev/mapper/centos-home 999G 990G 9.6G 100% /home
/dev/sda2 2.0G 169M 1.9G 9% /boot
/dev/sda1 2.0G 9.8M 2.0G 1% /boot/efi
tmpfs 571M 0 571M 0% /run/user/0
/dev/sdc1 3.7T 2.9T 782G 80% /HdD
/dev/sdd1 1.9T 1.8T 96G 95% /media/USBEXT/hdd
[root@webnoid hdd]# cd /HdD
[root@webnoid HdD]# ls
ls: reading directory .: Input/output error
[root@webnoid HdD]# umount /dev/sdc1
umount: /HdD: target is busy.
(In some cases useful info about processes that use
the device is found by lsof(8) or fuser(1))
[root@webnoid HdD]# umount -f /dev/sdc1
umount: /HdD: target is busy.
(In some cases useful info about processes that use
the device is found by lsof(8) or fuser(1))
[root@webnoid HdD]# umount -l /dev/sdc1
[root@webnoid HdD]# cd /dev/sdc1
-bash: cd: /dev/sdc1: No such file or directory
[root@webnoid HdD]# df -kh
Filesystem Size Used Avail Use% Mounted on
/dev/mapper/centos-root 155G 132G 24G 86% /
devtmpfs 2.8G 0 2.8G 0% /dev
tmpfs 2.8G 8.0K 2.8G 1% /dev/shm
tmpfs 2.8G 259M 2.6G 10% /run
tmpfs 2.8G 0 2.8G 0% /sys/fs/cgroup
/dev/mapper/centos-home 999G 990G 9.6G 100% /home
/dev/sda2 2.0G 169M 1.9G 9% /boot
/dev/sda1 2.0G 9.8M 2.0G 1% /boot/efi
tmpfs 571M 0 571M 0% /run/user/0
/dev/sdd1 1.9T 1.8T 96G 95% /media/USBEXT/hdd