offline-editing.html

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<h2>Offline Editing Guide</h2>

<p>
    It is often useful to inspect and edit a filesystem image without
    booting it as a VM.  You can mount a filesystem image under a
    mountpoint on your current filesystem.
</p>

<p>
    Say you have a filesystem image called "ttylinux-xen"
</p>

<p>

    The following makes the filesystem available for editing in your
    current (Linux) OS, in most cases you're required to be root:

<pre>mkdir tempmount
mount -o loop ttylinux-xen tempmount</pre>

</p>

<p>
    If you encountered a strange error (besides 'only root can do that') you
    may be missing loopback support from your kernel.
</p>

<p>
Make sure to un-mount the filesystem!

<pre>umount tempmount</pre>
</p>

<p>
    Note that is 'umount' and not 'unmount'. You can check that it was
    successfully un-mounted using 'ls' inspections (nothing should be in
    this 'tempmount' directory anymore) and by checking the currently
    mounted volumes using the 'df' command.
</p>

<p>
    If you get a message saying the volume is busy, you may have another
    terminal open whose current directory is under the 'tempmount'
    mountpoint or perhaps you are editing/viewing a file under this
    mountpoint?  Stopping all use of the volume (including a current
    terminal directory) will allow the un-mount to succeed.
</p>

<p>
    <i><b>WARNING:</b></i>
</p>
<p>
    Always remember to un-mount the filesystems ('umount'). If you boot this
    file as a VM filesystem while it is still mounted locally, you will have
    two kernels that think they have control over the same block device.
    That could, and likely will, lead to filesystem corruption.
</p>


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