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Latest commit 687880c Oct 7, 2016 @jthornber committed on GitHub Merge pull request #69 from mingnus/master-fix
[block-cache] Fix error handling in reading libaio events
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autoconf more build stuff Dec 9, 2011
base [many tools] fix bug in previous patch Jul 21, 2016
bin [thin_ls] First code drop. Jan 12, 2016
block-cache [block-cache] Fix error handling in reading libaio events Oct 6, 2016
caching [various] Improve documentation Jul 11, 2016
era [various] Improve documentation Jul 11, 2016
features [various] Improve documentation Jul 11, 2016
lib gmock stub Mar 22, 2013
man8 [various] Improve documentation Jul 11, 2016
persistent-data [various] Improve documentation Jul 11, 2016
thin-provisioning [various] Improve documentation Jul 11, 2016
unit-tests respect & use CPPFLAGS properly May 9, 2016
xml_metadata add some example metadata dumps Nov 16, 2011
.gitignore [all] Build a single executable Aug 27, 2014
.ruby-version Don't put a patch version in .rub-version, 1.9.3 is enough Dec 2, 2013
CHANGES update CHANGES Apr 5, 2016
COPYING Add copyright Dec 6, 2011
Gemfile Update gem requirements Jun 19, 2013
Gemfile.lock Update Gemfile Sep 4, 2014 [various] Improve documentation Jul 11, 2016 no need to supply held root, thin_dump -m will look it up Mar 4, 2016 Add a TODO file Apr 23, 2013
VERSION bump version Jul 21, 2016 add configure option to enable static linking Mar 9, 2016 Convert buffer_t to gmock. Mar 22, 2013 [base] introduce a command type that gets registered with the app Jan 8, 2016
mk_release make mk_release executable Mar 5, 2012 Dec 15, 2011


A suite of tools for manipulating the metadata of the dm-thin device-mapper target.


A C++ compiler that supports the c++11 standard (eg, g++). The Boost C++ library. The expat xml parser library (version 1). The libaio library (note this is not the same as the aio library that you get by linking -lrt) make, autoconf etc.

There are more requirements for testing, detailed below.


sudo make install

Quick examples

These tools introduce an xml format for the metadata. This is useful for making backups, or allowing scripting languages to generate or manipulate metadata. A Ruby library for this available; thinp_xml.

To convert the binary metadata format that the kernel uses to this xml format use thin_dump.

thin_dump --format xml /dev/mapper/my_thinp_metadata

To convert xml back to the binary form use thin_restore.

thin_restore -i my_xml -o /dev/mapper/my_thinp_metadata

You should periodically check the health of your metadata, much as you fsck a filesystem. Your volume manager (eg, LVM2) should be doing this for you behind the scenes.

thin_check /dev/mapper/my_thinp_metadata

Checking all the mappings can take some time, you can omit this part of the check if you wish.

thin_check --skip-mappings /dev/mapper/my_thinp_metadata

If your metadata has become corrupt for some reason (device failure, user error, kernel bug), thin_check will tell you what the effects of the corruption are (eg, which thin devices are effected, which mappings).

There are two ways to repair metadata. The simplest is via the thin_repair tool.

thin_repair -i /dev/mapper/broken_metadata_dev -o /dev/mapper/new_metadata_dev

This is a non-destructive operation that writes corrected metadata to a new metadata device.

Alternatively you can go via the xml format (perhaps you want to inspect the repaired metadata before restoring).

thin_dump --repair /dev/mapper/my_metadata > repaired.xml
thinp_restore -i repaired.xml -o /dev/mapper/my_metadata



If you've got the source from github you'll need to create the configure script with autoconf. I do this by running:


Enable tests

You will need to enable tests when you configure.

./configure --enable-testing

Unit tests

Unit tests are implemented using the google mock framework. This is a source library that you will have to download. A script is provided to do this for you.


All tests can be run via:

make unit-test

Alternatively you may want to run a subset of the tests:

make unit-tests/unit_tests
unit-tests/unit_tests --gtest_filter=BtreeTests.*

Functional tests

These top level tests are implemented using the cucumber tool. They check the user interface of the tools (eg, command line switches are accepted and effective).

I've provided a Gemfile, so installing this should be easy:

  • Install Ruby 1.9.x. I recommend doing this via RVM.
  • Make sure bundler is installed:

    gem install bundler

  • Install dependencies (including cucumber and thinp_xml)


Once you've done this you can run the tests with a simple:


Or specific tests with:

cucumber features/thin_restore -n 'print help'

Dump Metadata

To dump the metadata of a live thin pool, you must first create a snapshot of the metadata:

$ dmsetup message vg001-mythinpool-tpool 0 reserve_metadata_snap

Extract the metadata:

$ sudo bin/thin_dump -m /dev/mapper/vg001-mythinpool_tmeta
<superblock uuid="" time="1" transaction="2" data_block_size="128"nr_data_blocks="0">
    <device dev_id="1" mapped_blocks="1" transaction="0" creation_time="0" snap_time="1">
        <single_mapping origin_block="0" data_block="0" time="0"/>
    <device dev_id="2" mapped_blocks="1" transaction="1" creation_time="1" snap_time="1">
        <single_mapping origin_block="0" data_block="0" time="0"/>

Finally, release the root:

$ dmsetup message vg001-mythinpool-tpool 0 release_metadata_snap