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Accepted
Hamish Downer
Asked: 2010-08-03 05:43:37 +0800 CST

Is it possible to delete files when another filesystem is mounted on the path?

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Having just written an answer about moving /usr to a new partition I was wondering about deleting files once a new partition has been mounted. To use the example from the question, is it possible to mount a new partition on /usr and then delete all the files under /usr on the root partition to free up space on the root partition.

filesystem mount delete

1 Answers

  1. Best Answer

    Not directly, but there is a way around that: mount --bind is your friend:

    # Existing directory with a couple files in it
root@nkubuntu1004:~/test# ls testdir
bar  foo

# Mount a filesystem over existing directory
root@nkubuntu1004:~/test# mount -o loop testfs testdir
root@nkubuntu1004:~/test# ls testdir
lost+found

# Bind mount root filesystem to another directory
root@nkubuntu1004:~/test# mount --bind / bindmnt

# Can now get to contents of original directory through the bind mount
root@nkubuntu1004:~/test# ls bindmnt/root/test/testdir/
bar  foo

# Remove a file
root@nkubuntu1004:~/test# rm bindmnt/root/test/testdir/bar
root@nkubuntu1004:~/test# ls bindmnt/root/test/testdir/
foo
root@nkubuntu1004:~/test# ls testdir
lost+found

# Unmount filesystem
root@nkubuntu1004:~/test# umount testdir

# Observe the change having taken effect
root@nkubuntu1004:~/test# ls testdir
foo
root@nkubuntu1004:~/test#

    See also man mount -- search for "bind mounts".

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