diskrsync

package module

v0.0.0-...-5d039ae Latest Latest Go to latest Published: Jul 18, 2019 License: MIT Imports: 11 Imported by: 0

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README ¶

diskrsync -- rsync for block devices and disk images

This is a utility for remote backup of disk image files or devices. It uses ssh as a transport and tries to minimise the amount of data transferred. This is done by building a Merkle tree of blake2 hashes on both the source and the target hosts and then traversing the tree only transmitting those blocks where the hashes differ.

It is important that the source file does not change during the process. Typically this would be achieved by creating an LVM snapshot or by freezing the VM if that's not possible.

By default the resulting file is compressed using the spgz library (this can be disabled by using --no-compress flag). Note this only works on filesystems that support punching holes in files like xfs or ext4.

The utility handles sparse files (or just files with a lot of zeros) efficiently. The resulting file will be sparse (even if not compressed).

Size changes are also supported (both shrinks and expansions).

Installation

Install go. Version 1.7 is minimum required but the newer the better. If your distribution lacks the required version, check backports or updates (e.g. for debian or ubuntu) Alternatively, install manually.
Run the following commands:

mkdir workspace
cd workspace
export GOPATH=$(pwd)
go get github.com/dop251/diskrsync/diskrsync
sudo cp -a bin/diskrsync /usr/local/bin

Make sure the binary is copied to the remote machine as well. If the remote machine has a different CPU or OS you may want to use cross-compilation. For example if you are want to build a binary for ARM:

GOARCH=arm go get github.com/dop251/diskrsync/diskrsync
ls -l bin/linux_arm/diskrsync

Usage examples

diskrsync /dev/vg00/lv_snap ruser@backuphost:/mnt/backup/disk

This ensures that /mnt/backup/disk is up-to-date with the LV snapshot. The file will be compressed using spgz and can be recovered using the following command:

spgz -x /mnt/backup/disk /dev/vg00/....

diskrsync --verbose --no-compress --ssh-flags="-i id_file" /var/lib/libvirt/images/disk.img ruser@rbackuphost:/mnt/backup/

This ensures that /mnt/backup/disk.img is up-to-date with the source file.

Documentation ¶

Index ¶

Constants
Variables
func Source(reader io.ReadSeeker, size int64, cmdReader io.Reader, cmdWriter io.Writer, ...) (err error)
func Target(writer io.ReadWriteSeeker, size int64, cmdReader io.Reader, ...) (err error)
type CountingReader
- func (c *CountingReader) Count() int64
- func (r *CountingReader) Read(buf []byte) (n int, err error)
type CountingWriteCloser
- func (c *CountingWriteCloser) Count() int64
- func (r *CountingWriteCloser) Write(buf []byte) (n int, err error)

Constants ¶

View Source

const (
	DefTargetBlockSize = 128 * 1024
)

Variables ¶

View Source

var (
	ErrInvalidFormat = errors.New("Invalid data format")
)

Functions ¶

func Source ¶

func Source(reader io.ReadSeeker, size int64, cmdReader io.Reader, cmdWriter io.Writer, useBuffer bool, verbose bool) (err error)

func Target ¶

func Target(writer io.ReadWriteSeeker, size int64, cmdReader io.Reader, cmdWriter io.Writer, useBuffer bool, verbose bool) (err error)

Types ¶

type CountingReader ¶

type CountingReader struct {
	io.Reader
	// contains filtered or unexported fields
}

func (*CountingReader) Count ¶

func (c *CountingReader) Count() int64

func (*CountingReader) Read ¶

func (r *CountingReader) Read(buf []byte) (n int, err error)

type CountingWriteCloser ¶

type CountingWriteCloser struct {
	io.WriteCloser
	// contains filtered or unexported fields
}

func (*CountingWriteCloser) Count ¶

func (c *CountingWriteCloser) Count() int64

func (*CountingWriteCloser) Write ¶

func (r *CountingWriteCloser) Write(buf []byte) (n int, err error)

Source Files ¶

View all Source files

sync.go

Directories ¶

Path	Synopsis
diskrsync

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