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.
./configure make sudo make install
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.
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:
You will need to enable tests when you configure.
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:
Alternatively you may want to run a subset of the tests:
make unit-tests/unit_tests unit-tests/unit_tests --gtest_filter=BtreeTests.*
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'
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> <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"/> </device> </superblock>
Finally, release the root:
$ dmsetup message vg001-mythinpool-tpool 0 release_metadata_snap