[dm-crypt] force luksClose

Matthias Schniedermeyer ms at citd.de
Thu Nov 29 14:43:13 CET 2012

On 29.11.2012 14:02, Benjamin Eberhardt wrote:
> Dear dm-crypt developers,
> since a while I am using dm-crypt with luks on usb-attached external
> harddisks. Sometimes the usb connection breaks down and the harddisks
> get reconnected under different device names. It is then impossible to
> unmount (the "regular" way) and luksClose the "old" device which is
> still active. For unmounting i can use the "-l" "lazy" switch to kind
> of force unmounting of the luks'ed filesystem even though it is still
> "busy". A luksClose of the device although is impossible and the only
> way i know so far is to reboot the machine. Is it possible to
> implement some kind of lazy luksClose so that "dead" devices of which
> the physical layer has dissappeared can be removed?

1: Details
2: Works For Me

When the partition is `umount`able, IOW no program is accessing a file 
on the mount and nothing has a CWD inside the mount. I can umount such a 
mount-point without problems. Linux "recognizes" somehow when the 
backing-store is vanished and just does the umount.
Afterwards the loopaesClose(in my Case) also just works.

Only when you have anything that holds the mountpoint open, there is a 
problem. But that's a case for fuser/lsof and/or making sure that 
nothing like NFS prevents the mountpoint from being destroyed.

IOW. It's a problem of finding the culprit who holds the mountpoint 



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