incremental backup

Introduction

This article explains how to make incremental or differential backups, with a catalog available to restore (or export) at the point you want, with Butterfly Backup.

Requirements

Butterfly Backup is a simple wrapper of rsync written in python; the first requirement is python3.3 or higher (plus module cryptography for init action). Other requirements are openssh and rsync (version 2.5 or higher). Ok, let’s go!

[Editors note: rsync version 3.2.3 is already installed on Fedora 33 systems]

$ sudo dnf install python3 openssh rsync git
$ sudo pip3 install cryptography

Installation

After that, installing Butterfly Backup is very simple by using the following commands to clone the repository locally, and set up Butterfly Backup for use:

$ git clone https://github.com/MatteoGuadrini/Butterfly-Backup.git
$ cd Butterfly-Backup
$ sudo python3 setup.py
$ bb --help
$ man bb

To upgrade, you would use the same commands too.

Example

Butterfly Backup is a server to client tool and is installed on a server (or workstation). The restore process restores the files into the specified client. This process shares some of the options available to the backup process.

Backups are organized accord to precise catalog; this is an example:

$ tree destination/of/backup
.
├── destination
│ ├── hostname or ip of the PC under backup
│ │ ├── timestamp folder
│ │ │ ├── backup folders
│ │ │ ├── backup.log
│ │ │ └── restore.log
│ │ ├─── general.log
│ │ └─── symlink of last backup
│
├── export.log
├── backup.list
└── .catalog.cfg

Butterfly Backup has six main operations, referred to as actions, you can get information about them with the –help command.

$ bb --help
usage: bb [-h] [--verbose] [--log] [--dry-run] [--version] {config,backup,restore,archive,list,export} ... Butterfly Backup optional arguments: -h, --help show this help message and exit --verbose, -v Enable verbosity --log, -l Create a log --dry-run, -N Dry run mode --version, -V Print version action: Valid action {config,backup,restore,archive,list,export} Available actions config Configuration options backup Backup options restore Restore options archive Archive options list List options export Export options

Configuration

Configuration mode is straight forward; If you’re already familiar with the exchange keys and OpenSSH, you probably won’t need it. First, you must create a configuration (rsa keys), for instance:

$ bb config --new
SUCCESS: New configuration successfully created!

After creating the configuration, the keys will be installed (copied) on the hosts you want to backup:

$ bb config --deploy host1
Copying configuration to host1; write the password:
/usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/home/arthur/.ssh/id_rsa.pub"
/usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
/usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
arthur@host1's password: Number of key(s) added: 1 Now try logging into the machine, with: "ssh 'arthur@host1'"
and check to make sure that only the key(s) you wanted were added. SUCCESS: Configuration copied successfully on host1!

Backup

There are two backup modes: single and bulk.
The most relevant features of the two backup modes are the parallelism and retention of old backups. See the two parameters –parallel and –retention in the documentation.

Single backup

The backup of a single machine consists in taking the files and folders indicated in the command line, and putting them into the cataloging structure indicated above. In other words, copy all file and folders of a machine into a path.

This is an examples:

$ bb backup --computer host1 --destination /mnt/backup --data User Config --type Unix
Start backup on host1
SUCCESS: Command rsync -ah --no-links arthur@host1:/home :/etc /mnt/backup/host1/2020_09_19__10_28

Bulk backup

Above all, bulk mode backups share the same options as single mode, with the difference that they accept a file containing a list of hostnames or ips. In this mode backups will performed in parallel (by default 5 machines at a time). Above all, if you want to run fewer or more machines in parallel, specify the –parallel parameter.

Incremental of the previous backup, for instance:

$ cat /home/arthur/pclist.txt
host1
host2
host3
$ bb backup --list /home/arthur/pclist.txt --destination /mnt/backup --data User Config --type Unix
ERROR: The port 22 on host2 is closed!
ERROR: The port 22 on host3 is closed!
Start backup on host1
SUCCESS: Command rsync -ahu --no-links --link-dest=/mnt/backup/host1/2020_09_19__10_28 arthur@host1:/home :/etc /mnt/backup/host1/2020_09_19__10_50

There are four backup modes, which you specify with the –mode flag: Full (backup all files) , Mirror (backup all files in mirror mode), Differential (is based on the latest Full backup) and Incremental (is based on the latest backup).
The default mode is Incremental; Full mode is set by default when the flag is not specified.

Listing catalog

The first time you run backup commands, the catalog is created. The catalog is used for future backups and all the restores that are made through Butterfly Backup. To query this catalog use the list command.
First, let’s query the catalog in our example:

$ bb list --catalog /mnt/backup BUTTERFLY BACKUP CATALOG Backup id: aba860b0-9944-11e8-a93f-005056a664e0
Hostname or ip: host1
Timestamp: 2020-09-19 10:28:12 Backup id: dd6de2f2-9a1e-11e8-82b0-005056a664e0
Hostname or ip: host1
Timestamp: 2020-09-19 10:50:59

Press q for exit and select a backup-id:

$ bb list --catalog /mnt/backup --backup-id dd6de2f2-9a1e-11e8-82b0-005056a664e0
Backup id: dd6de2f2-9a1e-11e8-82b0-005056a664e0
Hostname or ip: host1
Type: Incremental
Timestamp: 2020-09-19 10:50:59
Start: 2020-09-19 10:50:59
Finish: 2020-09-19 11:43:51
OS: Unix
ExitCode: 0
Path: /mnt/backup/host1/2020_09_19__10_50
List: backup.log
etc
home

To export the catalog list use it with an external tool like cat, include the ––log flag:

$ bb list --catalog /mnt/backup --log
$ cat /mnt/backup/backup.list

Restore

The restore process is the exact opposite of the backup process. It takes the files from a specific backup and push it to the destination computer.
This command perform a restore on the same machine of the backup, for instance:

$ bb restore --catalog /mnt/backup --backup-id dd6de2f2-9a1e-11e8-82b0-005056a664e0 --computer host1 --log
Want to do restore path /mnt/backup/host1/2020_09_19__10_50/etc? To continue [Y/N]? y
Want to do restore path /mnt/backup/host1/2020_09_19__10_50/home? To continue [Y/N]? y
SUCCESS: Command rsync -ahu -vP --log-file=/mnt/backup/host1/2020_09_19__10_50/restore.log /mnt/backup/host1/2020_09_19__10_50/etc arthur@host1:/restore_2020_09_19__10_50
SUCCESS: Command rsync -ahu -vP --log-file=/mnt/backup/host1/2020_09_19__10_50/restore.log /mnt/backup/host1/2020_09_19__10_50/home/* arthur@host1:/home

Without specifying the “type” flag that indicates the operating system on which the data are being retrieved, Butterfly Backup will select it directly from the catalog via the backup-id.

Archive old backup

Archive operations are used to store backups by saving disk space.

$ bb archive --catalog /mnt/backup/ --days 1 --destination /mnt/archive/ --verbose --log
INFO: Check archive this backup f65e5afe-9734-11e8-b0bb-005056a664e0. Folder /mnt/backup/host1/2020_09_18__17_50
INFO: Check archive this backup 4f2b5f6e-9939-11e8-9ab6-005056a664e0. Folder /mnt/backup/host1/2020_09_15__07_26
SUCCESS: Delete /mnt/backup/host1/2020_09_15__07_26 successfully.
SUCCESS: Archive /mnt/backup/host1/2020_09_15__07_26 successfully.
$ ls /mnt/archive
host1
$ ls /mnt/archive/host1
2020_09_15__07_26.zip

After that, look in the catalog and see that the backup was actually archived:

$ bb list --catalog /mnt/backup/ -i 4f2b5f6e-9939-11e8-9ab6-005056a664e0
Backup id: 4f2b5f6e-9939-11e8-9ab6-005056a664e0
Hostname or ip: host1
Type: Incremental
Timestamp: 2020-09-15 07:26:46
Start: 2020-09-15 07:26:46
Finish: 2020-09-15 08:43:45
OS: Unix
ExitCode: 0
Path: /mnt/backup/host1/2020_09_15__07_26
Archived: True

Conclusion

Butterfly Backup was born from a very complex need; this tool provides superpowers to rsync, automates the backup and restore process. In addition, the catalog allows you to have a system similar to a “time machine”.

In conclusion, Butterfly Backup is a lightweight, versatile, simple and scriptable backup tool.

One more thing; Easter egg: bb -Vv

Thank you for reading my post.

Full documentation: https://butterfly-backup.readthedocs.io/
Github: https://github.com/MatteoGuadrini/Butterfly-Backup

Photo by Manu M on Unsplash.

Snapshots are an interesting feature of Btrfs. A snapshot is a copy of a subvolume. Taking a snapshot is immediate. However, taking a snapshot is not like performing a rsync or a cp, and a snapshot doesn’t occupy space as soon as it is created.

Editors note: From the BTRFS Wiki – A snapshot is simply a subvolume that shares its data (and metadata) with some other subvolume, using Btrfs’s COW capabilities.

Occupied space will increase alongside the data changes in the original subvolume or in the snapshot itself, if it is writeable. Added/modified files, and deleted files in the subvolume still reside in the snapshots. This is a convenient way to perform backups.

Using snapshots for backups

A snapshot resides on the same disk where the subvolume is located. You can browse it like a regular directory and recover a copy of a file as it was when the snapshot was performed. By the way, a snapshot on the same disk of the snapshotted subvolume is not an ideal backup strategy: if the hard disk broke, snapshots will be lost as well. An interesting feature of snapshots is the ability to send them to another location. The snapshot can be sent to an external hard drive or to a remote system via SSH (the destination filesystems need to be formatted as Btrfs as well). To do this, the commands btrfs send and btrfs receive are used.

Taking a snapshot

In order to use the send and the receive commands, it is important to create the snapshot as read-only, and snapshots are writeable by default.

The following command will take a snapshot of the /home subvolume. Note the -r flag for readonly.

sudo btrfs subvolume snapshot -r /home /.snapshots/home-day1

Instead of day1, the snapshot name can be the current date, like home-$(date +%Y%m%d). Snapshots look like regular subdirectories. You can place them wherever you like. The directory /.snapshots could be a good choice to keep them neat and to avoid confusion.

Editors note: Snapshots will not take recursive snapshots of themselves. If you create a snapshot of a subvolume, every subvolume or snapshot that the subvolume contains is mapped to an empty directory of the same name inside the snapshot.

Backup using btrfs send

In this example the destination Btrfs volume in the USB drive is mounted as /run/media/user/mydisk/bk . The command to send the snapshot to the destination is:

sudo btrfs send /.snapshots/home-day1 | sudo btrfs receive /run/media/user/mydisk/bk

This is called initial bootstrapping, and it corresponds to a full backup. This task will take some time, depending on the size of the /home directory. Obviously, subsequent incremental sends will take a shorter time.

Another useful feature of snapshots is the ability to perform the send task in an incremental way. Let’s take another snapshot.

sudo btrfs subvolume snapshot -r /home /.snapshots/home-day2

In order to perform the send task incrementally, you need to specify the previous snapshot as a base and this snapshot has to exist in the source and in the destination. Please note the -p option.

sudo btrfs send -p /.snapshot/home-day1 /.snapshot/home-day2 | sudo btrfs receive /run/media/user/mydisk/bk

And again (the day after):

sudo btrfs subvolume snapshot -r /home /.snapshots/home-day3

sudo btrfs send -p /.snapshot/home-day2 /.snapshot/home-day3 | sudo btrfs receive /run/media/user/mydisk/bk

Cleanup

Once the operation is complete, you can keep the snapshot. But if you perform these operations on a daily basis, you could end up with a lot of them. This could lead to confusion and potentially a lot of used space on your disks. So it is a good advice to delete some snapshots if you think you don’t need them anymore.

Keep in mind that in order to perform an incremental send you need at least the last snapshot. This snapshot must be present in the source and in the destination.

sudo btrfs subvolume delete /.snapshot/home-day1

sudo btrfs subvolume delete /.snapshot/home-day2

sudo btrfs subvolume delete /run/media/user/mydisk/bk/home-day1

sudo btrfs subvolume delete /run/media/user/mydisk/bk/home-day2

Note: the day 3 snapshot was preserved in the source and in the destination. In this way, tomorrow (day 4), you can perform a new incremental btrfs send.

As some final advice, if the USB drive has a bunch of space, you could consider maintaining multiple snapshots in the destination, while in the source disk you would keep only the last one.

Tag: incremental backup