Bind allows you to take a mounted partition and mount parts or all of it somewhere else in the file hierarchy. I'll show 4 different ways to accomplish this depending on how you want to use it. I will use as an example a data partition that I have set up in lieu of a dedicated /home partition at /Data. That partition is auto mounted in fstab as:
UUID=f7927995-b098-42be-ada0-987857f5177a /Data ext4 defaults,noatime 0 0
I have taken possession of the mounted partition: sudo chown altair /Data
And I have populated /Data with all the directories in a normal home directory: Documents, Downloads, Pictures, Videos, etc ...
[1] A Manual Bind - Good for that session only. Does not survive a reboot
The general syntax of the command looks like this:
sudo mount --bind /olddirectory /newdirectory
To unmount the bind:
sudo umount /newdirectory
So in this example:
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sudo mount --bind /Data/Documents /home/altair/Documents
If you have spaces in the path it has to have quotes around it like this:
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sudo mount --bind /windows/WinXP/"Documents and Settings/altair/My Documents" /home/altair/Documents
To "unbind" the directory:
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sudo umount /home/altair/Documents
* The same content is now accessible in two different places: In /Data and in /home/altair.
* Whatever you do in one happens to the other.
* The filesystem mount options will remain the same as those on the original mount point and you cannot change one without changing the other. Or in the case of a Windows fileystem ( i.e., NTFS ) not at all unless you change the mount options of the original mountpoint in fstab.
[2] Auto Mount at Boot using rc.local
You can use the same manual mount command ( without the sudo ) and add it to /etc/rc.local right above the "exit 0" line:
#!/bin/sh -e
#
# rc.local
#
# This script is executed at the end of each multiuser runlevel.
# Make sure that the script will "exit 0" on success or any other
# value on error.
#
# In order to enable or disable this script just change the execution
# bits.
#
# By default this script does nothing.
mount --bind /Data/Documents /home/altair/Documents
mount --bind /Data/Downloads /home/altair/Downloads
mount --bind /Data/Pictures /home/altair/Pictures
exit 0
[3] Auto Mount at Boot by creating your own Upstart script:
This is the method I now use by default since I can make sure that the bind operation only happens after the original partition is mounted.
Create an upstart job named "bind-home.conf"
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gksu gedit /etc/init/bind-home.conf
The content of that file would look like this:
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# Remount partitions with bind
#
description "Bind Data Partition Subdirectories to My Home Directory"
start on stopped mountall
script
mount --bind /Data/Documents /home/altair/Documents
mount --bind /Data/Downloads /home/altair/Downloads
mount --bind /Data/Pictures /home/altair/Pictures
end script
The "start on stopped mountall" insures that the bind commands will not be executed until all system mounts ( i.e., fstab ) are completed.
[4] Auto Mount at Boot in Fstab
NOTE: This is the traditional method and I have used it myself without issue until recently. Something has happened with mountall / upstart and who knows what else to make this a very unreliable method. I post it here in case the cause of the problem gets resolved. I have seen posts lately where this method is still being used with success so it may just be something unique with my setup but I urge caution.
The bind syntax and how you handle spaces changes in fstab and it must appear someplace after the line that identifies the mount of the original partition. So for example:
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UUID=f7927995-b098-42be-ada0-987857f5177a /Data ext4 defaults,noatime 0 0
/Data/Documents /home/altair/Documents auto bind 0 0
Or in the case of an NTFS partition with spaces in the path:
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UUID=DA9056C19056A3B3 /windows/WinXP ntfs defaults,uid=1000,gid=46,umask=007 0 0
/windows/WinXP/Documents\040and\040Settings/altair/My\040Documents /home/altair/Documents auto bind 0 0
I should note that another way to accomplish all this is simply to create a symbolic link from one location to the next. However, I live in a very networked environment with a combination of Windows, Macs, and Linux machines so I use Samba and the Samba client cannot follow symbolic links without modifying config files which Samba does not recommend.
