Introduction ============ A suite of tools for manipulating the metadata of the dm-thin, dm-cache and dm-era device-mapper targets. Requirements ============ A C++ compiler that supports the c++11 standard (eg, g++). The [Boost C++ library](http://www.boost.org/). The [expat](http://expat.sourceforge.net/) 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. A couple of non-essential tools are written in rust, and will require cargo and rustcc to be installed: thin_metadata_pack thin_metadata_unpack There are more requirements for testing, detailed below. Building ======== autoconf ./configure make sudo make install Building Rust tools =================== sudo make install-rust-tools 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](https://rubygems.org/gems/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 thin_restore -i repaired.xml -o /dev/mapper/my_metadata Development =========== Autoconf -------- If you've got the source from github you'll need to create the configure script with autoconf. I do this by running: autoreconf 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. ./get-gmock.sh 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 ---------------- A bunch of high level tests are implemented in the functional-tests directory. These tests are written in Scheme. To run them you'll need to install chezscheme (http://www.scheme.com/). There is no longer a dependency on the ThunderChez library. Make sure the tools that you wish to test are in your PATH. Then, cd funtional-tests ./run-tests run Other command are help and list. The test framework places temporary files under ./test-output/. By default the tests tidy up after themselves, just leaving a log file for each test. You can turn this off by using the --disable-unlink flag if you want all the artifacts left. 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 Finally, release the root: $ dmsetup message vg001-mythinpool-tpool 0 release_metadata_snap