umounting a mount --bind

PoP · 04-15-2011, 12:39 PM

Apologies, more a Unix than a Kindle question, but while trying avoid modifying the file system by using a "mount --bind" rather than creating a symbolic link I can't seem to be able to umount anymore (and must reboot to break the link).

For example, directory a contains file a.txt and directory b contains file b.txt

On Ubuntu everything works as I expected:

Code:

normand@5635C04:~$ ls a
a.txt
normand@5635C04:~$ ls b
b.txt
normand@5635C04:~$ sudo mount --bind b a
normand@5635C04:~$ ls a
b.txt
normand@5635C04:~$ ls b
b.txt
normand@5635C04:~$ sudo umount b
normand@5635C04:~$ ls a
a.txt
normand@5635C04:~$ ls b
b.txt
normand@5635C04:~$

On Kindle umount complains:

Code:

[root@kindle us]# ls a
a.txt
[root@kindle us]# ls b
b.txt
[root@kindle us]# mount --bind b a
[root@kindle us]# ls a
b.txt
[root@kindle us]# ls b
b.txt
[root@kindle us]# umount b
umount: b: not mounted
[root@kindle us]#

I Googled around and found that mount bind is often tricky but I am not experienced enough in Unix to figure it out. Welcoming a more expert suggestion.

NiLuJe · 04-15-2011, 02:12 PM

Unmount the target directory, not the source directory

.

(Might want to do a lazy (-l) unmount if it's something that might still be in use when you're unmounting).

PoP · 04-15-2011, 02:44 PM

Ah. Thanks NiLuJe. It confused me that it works differently than on Ubuntu.

Code:

[root@kindle us]# ls a
a.txt
[root@kindle us]# ls b
b.txt
[root@kindle us]# mount --bind b a
[root@kindle us]# ls a
b.txt
[root@kindle us]# ls b
b.txt
[root@kindle us]# umount b
umount: b: not mounted
[root@kindle us]# umount a
[root@kindle us]# ls a
a.txt
[root@kindle us]# ls b
b.txt

hawhill · 04-15-2011, 02:55 PM

That's because the mount/umount binaries on the Kindle do not have all the Whizz and Fiddles of the mount tool on Ubuntu. It's a downstripped version on the Kindle, for the sake of not spending precious space on the device. That's also true for other Unix tools on the device.

The umount on Ubuntu aims for comfort and - after not able to "really" umount b, it looks up the list of mounts and sees that b is mounted on a. It spares you the work of doing it "right" and does what you seem to want.

PoP · 04-15-2011, 03:13 PM

Quote:

Originally Posted by hawhill

It's a downstripped version on the Kindle, for the sake of not spending precious space on the device. That's also true for other Unix tools on the device.

Thanks for the explanation. Makes perfect sense. I am learning the lesson one bit at a time.

04-15-2011, 12:39 PM	#1
PoP ⁷⁄₉∈ᴮᴼᴿᴳ@₁₈% Posts: 366 Karma: 666665 Join Date: Dec 2010 Location: ♁ ᴺ₄₅°₃₀' ᵂ₇₃°₃₇' ±₆₀" Device: K3.₄ PRS-350 SGS3 Rπ	umounting a mount --bind Apologies, more a Unix than a Kindle question, but while trying avoid modifying the file system by using a "mount --bind" rather than creating a symbolic link I can't seem to be able to umount anymore (and must reboot to break the link). For example, directory a contains file a.txt and directory b contains file b.txt On Ubuntu everything works as I expected: Code: normand@5635C04:~$ ls a a.txt normand@5635C04:~$ ls b b.txt normand@5635C04:~$ sudo mount --bind b a normand@5635C04:~$ ls a b.txt normand@5635C04:~$ ls b b.txt normand@5635C04:~$ sudo umount b normand@5635C04:~$ ls a a.txt normand@5635C04:~$ ls b b.txt normand@5635C04:~$ On Kindle umount complains: Code: [root@kindle us]# ls a a.txt [root@kindle us]# ls b b.txt [root@kindle us]# mount --bind b a [root@kindle us]# ls a b.txt [root@kindle us]# ls b b.txt [root@kindle us]# umount b umount: b: not mounted [root@kindle us]# I Googled around and found that mount bind is often tricky but I am not experienced enough in Unix to figure it out. Welcoming a more expert suggestion.

04-15-2011, 02:44 PM	#3
PoP ⁷⁄₉∈ᴮᴼᴿᴳ@₁₈% Posts: 366 Karma: 666665 Join Date: Dec 2010 Location: ♁ ᴺ₄₅°₃₀' ᵂ₇₃°₃₇' ±₆₀" Device: K3.₄ PRS-350 SGS3 Rπ	Ah. Thanks NiLuJe. It confused me that it works differently than on Ubuntu. Code: [root@kindle us]# ls a a.txt [root@kindle us]# ls b b.txt [root@kindle us]# mount --bind b a [root@kindle us]# ls a b.txt [root@kindle us]# ls b b.txt [root@kindle us]# umount b umount: b: not mounted [root@kindle us]# umount a [root@kindle us]# ls a a.txt [root@kindle us]# ls b b.txt Last edited by PoP; 04-15-2011 at 02:46 PM.

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04-15-2011, 02:12 PM	#2
NiLuJe BLAM! Posts: 2,895 Karma: 2267781 Join Date: Jun 2010 Location: Paris, France Device: Kindle 2i, 3g, 4, 5w & PW	Unmount the target directory, not the source directory . (Might want to do a lazy (-l) unmount if it's something that might still be in use when you're unmounting).

04-15-2011, 02:55 PM	#4
hawhill Guru Posts: 769 Karma: 1646497 Join Date: Nov 2010 Location: Goettingen, Germany Device: Kindle Paperwhite, Kindle 3 WiFi	That's because the mount/umount binaries on the Kindle do not have all the Whizz and Fiddles of the mount tool on Ubuntu. It's a downstripped version on the Kindle, for the sake of not spending precious space on the device. That's also true for other Unix tools on the device. The umount on Ubuntu aims for comfort and - after not able to "really" umount b, it looks up the list of mounts and sees that b is mounted on a. It spares you the work of doing it "right" and does what you seem to want.


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