f



Rsync backups: storing differences only

	Keeping copies of incremental backups with rsync can be done by 
means of rsync'c --link-dest option. This is very nice, for it reduces 
the sizes quite dramatically. Howver, there is a situation that I would 
like to address:

	Imagine I have a file F. F is 100MB in size. I back it up the 
first day, and 100MB have to be copied. The second day the file is not 
changed, so rsync has to transfer no data. The second day backup, thanks 
to --link-dest option, is just a hard link from the first day backup.

	Now the third day I change F. I just add one byte to it. When the 
third day backup is launched, rsync only transfers that new, extra byte. 
Terrific. However, this third day backup is not a hard link from the 
first day backup any more, but a complete new copy of the original F, 
plus the new byte. I.e. another 100MB on disk, for the sake of a one byte 
difference.

	This is wasteful. What I would like is for the backup to keep 
just the differences for each file. Can this be done with rsync? Or with 
something else?
0
James
12/7/2016 7:31:04 PM
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On Wed, 7 Dec 2016 19:31:04 +0000 (UTC)
"James H. Markowitz" <noone@nowhere.net> wrote:

> 	Keeping copies of incremental backups with rsync can be done
> by means of rsync'c --link-dest option. This is very nice, for it
> reduces the sizes quite dramatically. Howver, there is a situation
> that I would like to address:
> 
> 	Imagine I have a file F. F is 100MB in size. I back it up the 
> first day, and 100MB have to be copied. The second day the file is
> not changed, so rsync has to transfer no data. The second day backup,
> thanks to --link-dest option, is just a hard link from the first day
> backup.
> 
> 	Now the third day I change F. I just add one byte to it. When
> the third day backup is launched, rsync only transfers that new,
> extra byte. Terrific. However, this third day backup is not a hard
> link from the first day backup any more, but a complete new copy of
> the original F, plus the new byte. I.e. another 100MB on disk, for
> the sake of a one byte difference.
> 
> 	This is wasteful. What I would like is for the backup to keep 
> just the differences for each file. Can this be done with rsync? Or
> with something else?

Maybe you can use the --delete option.

When I back up my home directory, I use rsync -av --delete.

-a, --archive               archive mode; equals -rlptgoD (no -H,-A,-X)

-v   "Shows what rsync is doing.

--delete                delete extraneous files from dest dirs


0
Johnny
12/7/2016 8:08:41 PM
At Wed, 7 Dec 2016 19:31:04 +0000 (UTC) "James H. Markowitz" <noone@nowhere.net> wrote:

> 
> 	Keeping copies of incremental backups with rsync can be done by 
> means of rsync'c --link-dest option. This is very nice, for it reduces 
> the sizes quite dramatically. Howver, there is a situation that I would 
> like to address:
> 
> 	Imagine I have a file F. F is 100MB in size. I back it up the 
> first day, and 100MB have to be copied. The second day the file is not 
> changed, so rsync has to transfer no data. The second day backup, thanks 
> to --link-dest option, is just a hard link from the first day backup.
> 
> 	Now the third day I change F. I just add one byte to it. When the 
> third day backup is launched, rsync only transfers that new, extra byte. 
> Terrific. However, this third day backup is not a hard link from the 
> first day backup any more, but a complete new copy of the original F, 
> plus the new byte. I.e. another 100MB on disk, for the sake of a one byte 
> difference.
> 
> 	This is wasteful. What I would like is for the backup to keep 
> just the differences for each file. Can this be done with rsync? Or with 
> something else?

If the File F is a *text* file, you can use a Source Code Versioning system, 
like subversion.  Otherwise, no.  Subvesion and the like store *differences* 
files.  So each revision is just the diffs of the files that changes.

>                              

-- 
Robert Heller             -- 978-544-6933
Deepwoods Software        -- Custom Software Services
http://www.deepsoft.com/  -- Linux Administration Services
heller@deepsoft.com       -- Webhosting Services
                                                                                                                             
0
Robert
12/7/2016 9:25:05 PM
On 2016-12-07 at 20:31, James H. Markowitz wrote:
> Can this be done with rsync? Or with something else?

Have a look at rdiff-backup.


-- 
mrg
0
marrgol
12/7/2016 10:43:23 PM
James H. Markowitz <noone@nowhere.net> wrote:
> [... rsync backs up whole file because of one byte change]
> 
>        This is wasteful. What I would like is for the backup to keep
> just the differences for each file.  Can this be done with rsync?  Or
> with something else?

Not with rsync, as rsync does not work that way.

What you might be looking for is Borg Backup:
https://borgbackup.readthedocs.io/en/stable/

0
Rich
12/8/2016 2:58:28 AM
On 2016-12-07, Johnny <johnny@invalid.net> wrote:
> On Wed, 7 Dec 2016 19:31:04 +0000 (UTC)
> "James H. Markowitz" <noone@nowhere.net> wrote:
>> This is wasteful. What I would like is for the backup to keep 
>> just the differences for each file. Can this be done with rsync? Or
>> with something else?
>
> Maybe you can use the --delete option.

Maybe James wants to keep the older versions of files around, so he can
restore them to the condition they were in on any day.  --delete doesn't
allow that, as far as I know.

Perhaps some version control system could do what you want, James.  I
have no experience with them, but I could see them not handling binary
files the way you want.  They should work for text files, and
possibly documents created by Linux office suites.
-- 
                                 Chick Tower

For e-mail:  colm DOT sent DOT towerboy AT xoxy DOT net
0
Chick
12/8/2016 3:48:29 AM
On 08/12/16 05:48, Chick Tower wrote:
> On 2016-12-07, Johnny <johnny@invalid.net> wrote:
>> On Wed, 7 Dec 2016 19:31:04 +0000 (UTC)
>> "James H. Markowitz" <noone@nowhere.net> wrote:
>>> This is wasteful. What I would like is for the backup to keep
>>> just the differences for each file. Can this be done with rsync? Or
>>> with something else?
>>
>> Maybe you can use the --delete option.
>
> Maybe James wants to keep the older versions of files around, so he can
> restore them to the condition they were in on any day.  --delete doesn't
> allow that, as far as I know.

My 2c worth:

Use a proper source control if you want to preserve versions, and use 
rsync --delete to back up.


>
> Perhaps some version control system could do what you want, James.  I
> have no experience with them, but I could see them not handling binary
> files the way you want.  They should work for text files, and
> possibly documents created by Linux office suites.
>

0
The
12/8/2016 7:22:07 AM
On 2016-12-07 20:31, James H. Markowitz wrote:
> 	Keeping copies of incremental backups with rsync can be done by 
> means of rsync'c --link-dest option. This is very nice, for it reduces 
> the sizes quite dramatically. Howver, there is a situation that I would 
> like to address:
> 
> 	Imagine I have a file F. F is 100MB in size. I back it up the 
> first day, and 100MB have to be copied. The second day the file is not 
> changed, so rsync has to transfer no data. The second day backup, thanks 
> to --link-dest option, is just a hard link from the first day backup.
> 
> 	Now the third day I change F. I just add one byte to it. When the 
> third day backup is launched, rsync only transfers that new, extra byte. 
> Terrific. However, this third day backup is not a hard link from the 
> first day backup any more, but a complete new copy of the original F, 
> plus the new byte. I.e. another 100MB on disk, for the sake of a one byte 
> difference.
> 
> 	This is wasteful. What I would like is for the backup to keep 
> just the differences for each file. Can this be done with rsync? Or with 
> something else?

Not with rsync, no, it stores whole files.

Possibilities (from my notes (lines too long, they wrap):

rdiff-backup    current copy is a mirror; older are rdifss.

  Convenient and transparent local/remote incremental mirror/backup

rdiff-backup backs up one directory to another, possibly over a network.
The target directory ends up a copy of the source directory, but extra
reverse diffs are stored in a special subdirectory of that target
directory, so you can still recover files lost some time ago. The idea
is to combine the best features of a mirror and an incremental backup.
rdiff-backup also preserves subdirectories, hard links, dev files,
permissions, uid/gid ownership, and modification times. Also,
rdiff-backup can operate in a bandwidth efficient manner over a pipe,
like rsync. Thus you can use rdiff-backup and ssh to securely back a
hard drive up to a remote location, and only the differences will be
transmitted. Finally, rdiff-backup is easy to use and settings have
sensical defaults.


Others that you could consider:

rsnapshot       current copy is a mirror; older are hardlinks and new files.

  gadmin-rsync?
  http://www.dirvish.org/
  pdumpfs (http://0xcc.net/pdumpfs)
  duplicity
  duply
  Back-In-Time (http://backintime.le-web.org/)
  LuckyBackup
  deja-dup
  dropbox
  duplicity
    Duplicity incrementally backs up files and directories by encrypting
    tar-format volumes with GnuPG and uploading them to a remote (or local)
    file server. In theory many remote backends are possible; right now
    local, ssh/scp, ftp, rsync, HSI, WebDAV, and Amazon S3 backends are
    written.

    Because duplicity uses librsync, the incremental archives are space
    efficient and only record the parts of files that have changed since
    the last backup. Currently duplicity supports deleted files, full unix
    permissions, directories, symbolic links, fifos, etc., but not hard
    links.


    rear - Relax and Recover (ReaR) is a Linux Disaster Recovery framework

  Relax and Recover (abbreviated rear) is a highly modular disaster recovery
  framework for GNU/Linux based systems, but can be easily extended to other
  UNIX alike systems. The disaster recovery information (and maybe the
  backups) can be stored via the network, local on hard disks or USB
devices,
  DVD/CD-R, tape, etc. The result is also a bootable image that is
capable of
  booting via PXE, DVD/CD and USB media. Relax and Recover integrates with
  other backup software and provides integrated bare metal disaster recovery
  abilities to the compatible backup software.




        storeBackup - A disk-to-disk backup tool for Linux

  It uses hardlinks for deduplication, deletes backups
  after some time (or number of backups) and offers optional compression.
    Personally, I like that storeBackup slices big VM harddisk files into
  smaller pieces and deduplicates them effectively reducing the size needed
  for a subsequent backup. (Jan Ritzerfeld).
                --
  storeBackup is a disk-to-disk backup tool for Linux. It
  should run on other Unix like machines.  You can directly browse
through the
  backuped files (locally, via NFS, via SAMBA or whatever).  This gives the
  users the possibility to restore files absolutely easily and fast.  He/She
  only has to copy (and possibly uncompress) the file.  The is also a
tool for
  easily restoring (sub) trees for the administrator.  Every single
backup of
  a specific time can be deleted without affecting the other existing
backups.
  Before you can start using storeBackup, please carefully read
  /usr/share/doc/packages/storeBackup/README and create an appropriate
  configuration file /etc/storebackup.d/storebackup.config using
  /usr/share/doc/packages/storeBackup/storebackup.config.default as a
  template.

-- 
Cheers, Carlos.
0
Carlos
12/8/2016 12:22:08 PM
On 2016-12-08, Chick Tower <c.tower@deadspam.com> wrote:
> On 2016-12-07, Johnny <johnny@invalid.net> wrote:
>> On Wed, 7 Dec 2016 19:31:04 +0000 (UTC)
>> "James H. Markowitz" <noone@nowhere.net> wrote:
>>> This is wasteful. What I would like is for the backup to keep 
>>> just the differences for each file. Can this be done with rsync? Or
>>> with something else?
>>
>> Maybe you can use the --delete option.
>
> Maybe James wants to keep the older versions of files around, so he can
> restore them to the condition they were in on any day.  --delete doesn't
> allow that, as far as I know.
>
> Perhaps some version control system could do what you want, James.  I
> have no experience with them, but I could see them not handling binary
> files the way you want.  They should work for text files, and
> possibly documents created by Linux office suites.

The problem with such incremental backups is that you have unroll the
whole thing. So to recover a file, you have to go way back and recover
the original and then apply all of the updates one by one, in order.
I have 5 years of rsync backup and the whole thing is only about three
times the size of a single day's backup.
And if I want to recover from 2 years ago, I just copy over the file,
and that is it. 


0
William
12/8/2016 2:57:24 PM
	Thanks everybody for your feedback. It would seem that rdiff-
backup might do what I need.

0
James
12/8/2016 6:04:00 PM
On 2016-12-08, James H. Markowitz <noone@nowhere.net> wrote:
> 	Thanks everybody for your feedback. It would seem that rdiff-
> backup might do what I need.
>

It might do what you need, but it doesn't do what you previously asked.
It still stores whole files, not just differences in individual files.
It does minimize the space you need for backups, though, and allows you
to recover files as of any date you ran rdiff-backup.  Unless you've
purged older copies of files, but you don't do that until you know you
don't want them any more.  It's not automatic.
-- 
                                 Chick Tower

For e-mail:  colm DOT sent DOT towerboy AT xoxy DOT net
0
Chick
12/9/2016 4:26:59 AM
On 2016-12-09 05:26, Chick Tower wrote:
> On 2016-12-08, James H. Markowitz <noone@nowhere.net> wrote:
>> 	Thanks everybody for your feedback. It would seem that rdiff-
>> backup might do what I need.
>>
> 
> It might do what you need, but it doesn't do what you previously asked.
> It still stores whole files, not just differences in individual files.

According to its documentation, it does store differences to the first copy.

-- 
Cheers,
       Carlos E.R.
0
Carlos
12/9/2016 11:11:23 AM
On 2016-12-07, James H. Markowitz <noone@nowhere.net> wrote:
> 	Keeping copies of incremental backups with rsync can be done by 
> means of rsync'c --link-dest option. This is very nice, for it reduces 
> the sizes quite dramatically. Howver, there is a situation that I would 
> like to address:
>
> 	Imagine I have a file F. F is 100MB in size. I back it up the 
> first day, and 100MB have to be copied. The second day the file is not 
> changed, so rsync has to transfer no data. The second day backup, thanks 
> to --link-dest option, is just a hard link from the first day backup.
>
> 	Now the third day I change F. I just add one byte to it. When the 
> third day backup is launched, rsync only transfers that new, extra byte. 
> Terrific. However, this third day backup is not a hard link from the 
> first day backup any more, but a complete new copy of the original F, 
> plus the new byte. I.e. another 100MB on disk, for the sake of a one byte 
> difference.
>
> 	This is wasteful. What I would like is for the backup to keep 
> just the differences for each file. Can this be done with rsync? Or with 
> something else?

You don't wanna do that. Because in that scenario, every single version of
that backup potentialy needs to be perfect, to recompose and restore.
Very fragile...

 

-- 
When in doubt, use brute force.
                -- Ken Thompson
0
Rikishi42
12/11/2016 9:17:42 PM
On 2016-12-11, Rikishi42 <skunkworks@rikishi42.net> wrote:
> On 2016-12-07, James H. Markowitz <noone@nowhere.net> wrote:
>> 	Keeping copies of incremental backups with rsync can be done by 
>> means of rsync'c --link-dest option. This is very nice, for it reduces 
>> the sizes quite dramatically. Howver, there is a situation that I would 
>> like to address:
>>
>> 	Imagine I have a file F. F is 100MB in size. I back it up the 
>> first day, and 100MB have to be copied. The second day the file is not 
>> changed, so rsync has to transfer no data. The second day backup, thanks 
>> to --link-dest option, is just a hard link from the first day backup.
>>
>> 	Now the third day I change F. I just add one byte to it. When the 
>> third day backup is launched, rsync only transfers that new, extra byte. 
>> Terrific. However, this third day backup is not a hard link from the 
>> first day backup any more, but a complete new copy of the original F, 
>> plus the new byte. I.e. another 100MB on disk, for the sake of a one byte 
>> difference.
>>
>> 	This is wasteful. What I would like is for the backup to keep 
>> just the differences for each file. Can this be done with rsync? Or with 
>> something else?
>
> You don't wanna do that. Because in that scenario, every single version of
> that backup potentialy needs to be perfect, to recompose and restore.
> Very fragile...


It also means that to restore you need to unroll all of those partial
files. Say it is 200 days worth. You have to unroll 200 separate file.
Yes, you saved some disk space (at mahy TB per $100 these days that's
not exactly expensive at the cost of a huge cost in time during restore.
The tradeoff is not  worth it IMHO. As I said I have 4 years saved (7
days, 4 weeks, 12 months, 4 yearly) and it costs about a factor of 2 in
disk
space (ie about twice as much disk space as is currently on the system)
Most files never change. A few do.

Note that rsync also has its potential problems. If any one of those
hard linked files gets changed for some reason, then all are changed.
Ie, there is only one version of all those 27 saved versions of a file
which never changed.
So don't think of it as 27 saved versions. But one is far far better
than
0

>
>  
>
0
William
12/12/2016 12:52:19 AM
On 2016-12-09, Carlos E. R. <robin_listas@invalid.es> wrote:
> On 2016-12-09 05:26, Chick Tower wrote:
>> On 2016-12-08, James H. Markowitz <noone@nowhere.net> wrote:
>>> 	Thanks everybody for your feedback. It would seem that rdiff-
>>> backup might do what I need.
>>>
>> 
>> It might do what you need, but it doesn't do what you previously asked.
>> It still stores whole files, not just differences in individual files.
>
> According to its documentation, it does store differences to the first copy.

You're right, the documentation does make it look like it stores file
differences, not just whole changed files.  So I mounted my trusty (so
far) backup drive and looked at some of the change files from
rdiff-backup.  They do appear to be just the differences from one
version of text files to the next, which are then gzipped.  I use rdiff-
backup only on my home partition, so there weren't many binary files for 
me to check, and I wouldn't be sure how to check them, anyway.
-- 
                                 Chick Tower

For e-mail:  colm DOT sent DOT towerboy AT xoxy DOT net
0
Chick
12/12/2016 6:55:40 PM
On 2016-12-12 19:55, Chick Tower wrote:
> On 2016-12-09, Carlos E. R. <> wrote:
>> On 2016-12-09 05:26, Chick Tower wrote:
>>> On 2016-12-08, James H. Markowitz <> wrote:
>>>> 	Thanks everybody for your feedback. It would seem that rdiff-
>>>> backup might do what I need.
>>>>
>>>
>>> It might do what you need, but it doesn't do what you previously asked.
>>> It still stores whole files, not just differences in individual files.
>>
>> According to its documentation, it does store differences to the first copy.
> 
> You're right, the documentation does make it look like it stores file
> differences, not just whole changed files.  So I mounted my trusty (so
> far) backup drive and looked at some of the change files from
> rdiff-backup.  They do appear to be just the differences from one
> version of text files to the next, which are then gzipped.  I use rdiff-
> backup only on my home partition, so there weren't many binary files for 
> me to check, and I wouldn't be sure how to check them, anyway.

Well, check the size... if they are smaller than the original, it is
storing differences.

Or try "file" on them, after decompressing.

-- 
Cheers,
       Carlos E.R.
0
Carlos
12/12/2016 9:02:23 PM
Reply: