Ploop/Mount helpers - Revision history

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2021-03-10T15:25:02Z

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2014-01-23T19:03:25Z

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Kir: Kir moved page Ploop/mount helpers to Ploop/Mount helpers

2013-11-21T02:25:19Z

Kir moved page Ploop/mount helpers to Ploop/Mount helpers

Kir: created

2013-11-21T02:24:04Z

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2013-11-21T02:07:22Z

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New page

Despite the fact that ploop is not a file system, a trick exist
to make it look and feel like so -- i.e. to use usual <code>mount</code>
and <code>umount</code> commands rather than the {{Man|ploop|8}} tool.
This article describes why and how, and lists caveats and limitation.

== Introduction ==

ploop is not a filesystem per se, but a kernel [[w:loop device]] driver, providing a way
to represent a ploop image (or a set of stacked images) as a
[[w:Device file system#Block_devices|block device]].
On top of that block device provided by ploop, an ext4 file system
is created and used, for example, for storing files of a specific
container.

Therefore a complete ploop mount consists of two steps:
# "mount" ploop image(s) to create a ploop device (/dev/ploopNNNNN)
# mount a filesystem residing on this ploop device to a mount point

For simplicity, these two are usually wrapped to be done together in one step (say when you use ploop mount with -m option).
In reality, step 1 is kernel assembling a device out of image(s), and step 2 is the real mount.

== Mounting ==

Normally, ploop is mounted by <code>ploop mount</code> command.

You can use the following syntax to mount a ploop device and the filesystem inside it:

mount -t ploop [option ...] /path/to/DiskDescriptor.xml /mount/point

The following options are supported:

<code>-r</code>, <code>-o ro</code>
: mount read-only

<code>-v</code>, <code>--verbose</code>
: be more verbose

<code>-f</code>, <code>--fake</code>
: do everything except for the actual mount

<code>-n</code>, <code>--no-mtab</code>, <code>-s</code>
: these options are deliberately ignored

== Unmounting ==

Normally, ploop is unmounted by <code>ploop umount</code> command.

But if the following is true, usual <code>umount</code> can be used:
# /etc/mtab is a separate file (not a symlink to /proc/mounts);
# mounting should have been done using <code>mount</code> (not <code>ploop mount</code>).

Any of the following can be used:

umount /path/to/DiskDescriptor.xml
umount /mount/point

[[Category: ploop]]

@@ Line 1: / Line 1: @@
 Despite the fact that ploop is not a file system, a trick exist
 to make it look and feel like so — i.e. to use usual <code>mount</code>
@@ Line 69: / Line 70: @@
 * [[Ploop]]
 * {{Bug|2817}}
 [[Category: Storage]]

← Older revision		Revision as of 19:03, 23 January 2014
Line 70:		Line 70:
	* {{Bug\|2817}}		* {{Bug\|2817}}

−	[[Category: ~~ploop~~]]	+	[[Category: Storage]]

@@ Line 1: / Line 1: @@
 Despite the fact that ploop is not a file system, a trick exist
 to make it look and feel like so — i.e. to use usual <code>mount</code>
@@ Line 6: / Line 4: @@
 This article describes how it works and can be used.
-== Introduction == <!--T:2-->
+== Introduction ==
 ploop is not a filesystem per se, but a kernel [[w:loop device]] driver, providing a way
 to represent a ploop image (or a set of stacked images) as a
@@ Line 16: / Line 13: @@
 container.
 Therefore a complete ploop mount consists of two steps:
 # "mount" ploop image(s) to create a ploop device (/dev/ploopNNNNN)
 # mount a filesystem residing on this ploop device to a mount point
 For simplicity, these two are usually wrapped to be done together in one step (say when you use ploop mount with -m option).
 In reality, step 1 is kernel assembling a device out of image(s), and step 2 is the real mount.
-== Mounting == <!--T:6-->
+== Mounting ==
 You can use the following syntax to mount a ploop device and the filesystem inside it:
-  <!--T:8-->
+  mount -t ploop [option ...] /path/to/DiskDescriptor.xml /mount/point
 The following options are supported:
 <code>-r</code>, <code>-o ro</code>
 : mount read-only
 <code>-v</code>, <code>--verbose</code>
 : be more verbose
 <code>-f</code>, <code>--fake</code>
 : do everything except for the actual mount
 <code>-n</code>, <code>--no-mtab</code>, <code>-s</code>
 : these options are deliberately ignored
-== Unmounting == <!--T:14-->
+== Unmounting ==
 To unmount, DiskDescriptor can be specified:
-  <!--T:16-->
+  umount /path/to/DiskDescriptor.xml
 A mount point can be used as well:
-  <!--T:18-->
+  umount /mount/point
-== Limitations == <!--T:19-->
+== Limitations ==
 Note that umount can only work if:
 # /etc/mtab is a separate file (not a symlink to /proc/mounts);
 # mounting was done using <code>mount</code> (not <code>ploop mount</code>).
 Otherwise, umount binary will not be able to find <code>ploop</code> as the "filesystem"
 field in /etc/mtab, and will not call <code>umount.ploop</code> helper. As a result,
 file system will be unmounted, but ploop device itself will stay mounted.
-== Alternative == <!--T:22-->
+== Alternative ==
 <code>ploop mount</code> and <code>ploop umount</code> commands,
 as described in {{Man|ploop|8}} man page.
-== See also == <!--T:24-->
+== See also ==
 * [[Ploop]]
 * {{Bug|2817}}
 [[Category: Storage]]

← Older revision	Revision as of 02:25, 21 November 2013
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