Ubuntu – How to umount / ? It’s busy

mountUbuntuumount

I'm trying to use zerofree, which seems to be the answer for this: How to reduce VM size?

I have successfully umounted /dev/sda1, and zerofree worked fine, releasing ~37gb.

But I can't seem to umount or remount as read only /dev/mapper/mypc-root, it says:

umount: / is busy

or

mount: / is busy

The commands used were:

$ umount /dev/mapper/mypc-root
$ mount -no remount,ro -t ext2 /dev/mapper/mypc-root /

I'm in single user mode, entered it with 'init 1'.

The guest SO is Ubuntu 12, with encrypted LVM and home.

Any ideas?

Best Answer

/ can't be unmounted from the system, as / is in use (thus the message you see) by the system itself.

You will need to do this procedure from a Live-CD.

Related Solutions

UNIX – mount: only root can do that

When mounting a volume as a regular user, you only need to provide the mount point name, i.e.:

mount /mnt/sdcard

The /etc/fstab file provides the device that will be used.

VirtualBox – How to Reduce VM Size in Ubuntu

From the manual:

For this operation to be effective, it is required that free space in the guest system first be zeroed out using a suitable software tool. For Windows guests, you can use the sdelete tool provided by Microsoft. Execute sdelete -c in the guest to zero the free disk space before compressing the virtual disk image. For Linux, use the zerofree utility which supports ext2/ext3 filesystems.

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