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https://github.com/fdupoux/fsarchiver

file system archiver for linux
https://github.com/fdupoux/fsarchiver

backup cloning compression ext4 filesystem linux multithreaded xfs

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file system archiver for linux

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README 

        
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fsarchiver: Filesystem Archiver for Linux [http://www.fsarchiver.org]

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About FSArchiver

----------------

FSArchiver is a system tool that allows you to save the contents of a

filesystem to a compressed archive file. The filesystem contents can be

restored on a device which has a different size and it can be restored on a

different filesystem. Unlike tar/dar, FSArchiver also creates the

filesystem when it extracts the data to devices. Everything is checksummed

in the archive in order to protect the data. If the archive is corrupt, you

just lose the current file, not the whole archive. FSArchiver is released

under the GPLv2 license. You should read the Quick Start guide

[http://www.fsarchiver.org/quickstart/] if you are using FSArchiver for the

first time.



Detailed description

--------------------

The purpose of this project is to provide a safe and flexible filesystem

backup/deployment tool. Other open-source filesystems tools such as

Partimage already exist. These tools are working at the filesystem block

level, so it's not possible to restore the backup to a smaller device, and

restoring to a bigger one forces you to resize the filesystem by hand.



The purpose is to have a very flexible program. FSArchiver can extract an

archive to a device which is smaller that the original one as long as there

is enough space to store the data. It can also restore the data on a

different filesystem, so you can use it when you want to convert your

filesystem: you can backup an EXT3 filesystem, and restore it as ReiserFS.



FSArchiver works at the file level. It can make an archive of most Linux

filesystems (EXT3, ReiserFS, XFS, ...) that the running kernel can mount

with read-write support. It will preserve all the standard Unix file

attributes (permissions, timestamps, symbolic-links, hard-links,

extended-attributes, ...), as long as the kernel has support for them

enabled.



Limitations

-----------

There are limitations anyway: FAT filesystem is supported basically for EFI

System Partition volumes (UEFI systems) and won't work for bootable Windows

volumes. Also, NTFS support is experimental and shouldn't be used in

production. FSArchiver won't preserve features which are very specific to a

filesystem. For instance, if you create a snapshot in a Btrfs volume,

FSArchiver won't know anything about that, and it will just backup the

contents seen when you mount the device.



FSArchiver is safe when it makes backups of devices which are not mounted

or are mounted read-only. There is an option to force the backup of a

read-write mounted volume, but there may be problems with the files that

changed during the backup. If you want to backup a device which are in use,

the best thing to do is to make an LVM snapshot of it using lvcreate -s,

which is part of the LVM userland tools. Unfortunately you can only make

snapshots of devices which are LVM Logical Volumes.



Protection against data loss

----------------------------

FSArchiver is using two levels of checksums to protect your data against

corruption. Each block of each file has a 32-bit checksum written in the

archive. That way we can identify which block of your file is damaged. Once

a file has been restored, the MD5 checksum of the whole file is compared to

the original MD5. It's a 128-bit checksum, so it will detect all file

corruptions. In case one file is damaged, FSArchiver will restore all the

other files from your archive, so you won't lose all your data. It's very

different from tar.gz where the whole tar is compressed with gzip. In that

case, the data which are written after the corruption are lost.

FSArchiver-0.2.3 and newer versions are able to ignore corrupt contents in

an archive file, so all the other files will be restored.