How to unmount a busy device

Question

I've got some samba drives that are being accessed by multiple users daily. I already have code to recognize shared drives (from a SQL table) and mount them in a special directory where all users can access them.

I want to know, if I remove a drive from my SQL table (effectively taking it offline) how, or even is, there a way to unmount a busy device? So far I've found that any form of umount does not work.

Ignoring the possibility of destroying data - is it possible to unmount a device that is currently being read?

Answer 1

YES!! There is a way to detach a busy device immediately - even if it is busy and cannot be unmounted forcefully. You may cleanup all later:

umount -l /PATH/OF/BUSY-DEVICE umount -f /PATH/OF/BUSY-NFS (NETWORK-FILE-SYSTEM) 

NOTE/CAUTION

1. These commands can disrupt a running process, cause data loss OR corrupt open files. Programs accessing target DEVICE/NFS files may throw errors OR could not work properly after force unmount.
2. Do not execute above umount commands when inside mounted path (Folder/Drive/Device) itself. First, you may use pwd command to validate your current directory path (which should not be the mounted path), then use cd command to get out of the mounted path - to unmount it later using above commands.

Answer 2

If possible, let us locate/identify the busy process, kill that process and then unmount the samba share/ drive to minimize damage:

• lsof | grep '<mountpoint of /dev/sda1>' (or whatever the mounted device is)

• pkill target_process (kills busy proc. by name | kill PID | killall target_process)

• umount /dev/sda1 (or whatever the mounted device is)