Laptop/Server Data Synchronization?

gbr writes "I've been trying to automatically synchronize data between a laptop and a server. When the laptop is connected to the network, I want all writes to automatically propagate across to the server. When the laptop is disconnected I want the laptop user to continue working with the local data. When the laptop is reconnected, I want the data to automatically re-sync. The issue is, the data on the server may have changed as well, which needs to propagate back to the laptop. The data doesn't contain anything too special, no database tables etc. It does contain binary data such as executables and word processing documents. I've looked at ChironFS, Unison file sync, and drbd. ChironFS needs a manual rebuild if a connection fails, and the user needs to know which machine contains the correct data. Unison requires the user to initiate the synchronization process manually every time, and drbd is just not meant for the job at hand. How do you automatically, and invisibly to the user (except in the case of conflicts), synchronize between a laptop and a server?"

Comments

rsync

[jshriverWVU]

I do this often and rsync is wonderful for such a task.

Re:rsync

[pixel.jonah]

I'd second rsync.

I'd also take a look at Microsoft's SyncToy if you're on win***s.

Re:rsync

[rebullandvodka]

I agree, subversion & scripts sounds like a good solution. Dare I suggest... Lotus Notes/Domino? Seriously, the notes databases can be setup to do what you're looking for. It worked pretty good at my last job as long as everyone played nice.

Re:rsync

[eos_buddy]

If the laptop and the server you use is Linux/Unix, rsync is definitely the answer to it - its robust and after the 1st time of rsyncing, the process should be quick enough (assuming you log-on often). I wrote a small script recently to sync my firefox bookmarks. Don't know whether it might be helpful to you, but here is the link: http://oidw.blogspot.com/2007/08/geek-talk.html

Re:rsync

[Roarkk]

rsync is part of the answer. If you're looking for a way to have multiple, incremental backups of laptops with unpredicatable patterns of connecting to the network, BackupPC is the way to go.

BackupPC is a high-performance, enterprise-grade system for backing up Linux and WinXX PCs and laptops to a server's disk. BackupPC is highly configurable and easy to install and maintain. Given the ever decreasing cost of disks and raid systems, it is now practical and cost effective to backup a large number of machines onto a server's local disk or network storage. This is what BackupPC does. For some sites, this might be the complete backup solution. For other sites, additional permanent archives could be created by periodically backing up the server to tape. A variety of Open Source systems are available for doing backup to tape. BackupPC is written in Perl and extracts backup data via SMB using Samba, tar over ssh/rsh/nfs, or rsync. It is robust, reliable, well documented and freely available as Open Source on SourceForge.
By using pooling and compression, one client of mine is using BackupPC to backup over 1TB of data distributed among over 100 laptops to a 200GB filesystem on a central server. The network is polled every hour, and any system that hasn't been backed up in the last 24 hours is queued. Beautiful system.

Re:rsync

[Anonymous Coward]

I keep trying to install the n'sync CD but it just asks me whether I want to play the music or not.

Re:rsync

[frenetic3]

Take a look at Dropbox (http://getdropbox.com/; screencast at http://getdropbox.com/u/2/screencast.html) if you want something that's rsync-like but integrated into Windows and OS X. It's in beta (and full disclosure: I co-founded the company) but was designed precisely because there's nothing out there that does this well and is easy to use.

Re:rsync

[syphax]

Unison is 2-way rsync. But as the poster noted, unison/rsync doesn't easily support automatic synching (that I know of)- you have to kick it off and then deal with any conflicts, etc., manually. I think the poster is looking for ideas of at least automating Unison/rsync (BTW does rsync support 2-way updating, as the poster explicitly mentions?).

As someone who relies on running unison manually (too lazy to figure out how to automate on my Windows box), I'd be interested in relevant solutions.

Re:rsync

[cduffy]

subversion is intended for a case where you have a single data store. A modern distributed SCM -- designed for disconnected use -- would make more sense.

Personally, I play with bzr most frequently; it has a nifty Python interface (and an extensive plugin architecture) which makes it quite conducive to local scriptage. (As an example -- I have a local, filesystem-backed set of CA scripts which use bzr for transactional semantics; if a method is called which throws an exception, all filesystem changes are automatically rolled back; if a method succeeds, a commit is done to record the operation and [effectively] set a rollback point). The separation between working tree and repository is optional (by default, all working trees are also repositories -- much like BitKeeper in that respect), which makes it very handy for situations like this where you don't necessarily *have* a separate, central location which all nodes can always communicate with, and where the different trees are allowed and expected to temporarily diverge.

Re:rsync

[EvanED]

The information on how to use this hack is not publicly available.

Um... what?

You mean besides this diagram of the steps you should follow when making a backup (and a similar one for restore), and the MSDN documentation for the VSS.

Re:rsync

[arivanov]

There is no point implementing laptop backups before implementing a no-quota IMAP mail server. Exchange in its native mode does not count due to a number of corruption bugs which hit you once your inbox exceeds 2G (it should be OK as an IMAP server, bugs are mostly in Outlook).
As far as the user is concerned his primary concern for laptop data loss is email. So you have to back it up as a part of any backup solution. If you are storing email locally on the laptop and backing it up the backup will nearly always be corrupt due to file locking. Further to this, the financial, network and storage resource required to implement a laptop backup solution exceeds by far the cost of extra storage on the mail server. In addition to that if the email is stored centrally the backup size per laptop decreases straight away to become on the order of MBs instead of GBs for most users.

Re:rsync

[frenetic3]

Apologies if it's in bad taste to reply to my own post, especially because it's about the product I'm working on, but here are some of Dropbox's differences/improvements over what people typically hack together themselves:

- syncs continuously/watches the FS for file changes (no cron jobs needed -- things usually sync as quickly as they can be sent)
- does binary diffing and only sends deltas (compressed & over SSL)
- transparently archives past versions of all files (i.e. undelete/infinite undo)
- syncs across any number of machines
- lets you get to your files from the web
- some more info @ http://venturebeat.com/2007/08/16/the-y-combinator -list/

We made it after hacking together our own rsync-based abominations and getting really annoyed that no one had solved this genre of problems in a way that normal people could use.

Okay, I can stop shilling now. I was just excited that other people run into these problems.

Re:rsync

[Jimithing DMB]

This looks quite similar to Novell's iFolder but with you running the server yourselves instead of having your users set up an iFolder server. Last I used iFolder was in the 1.x or 2.x days and it frankly wasn't anywhere near the polished product you have here. Now it seems that iFolder 3.x is open source and looks a lot more polished.

Still, I think you surely have a great service market here even though the polished front-end app seems to now be done open source. Best of luck to you on your new venture!

Re:rsync

[dusty123]

I don't see how rsync solves this problem:

AFAIK, rsync is only one-way, meaning that it overwrites and eventually deletes files. Have a try:

mkdir d1 d2 # Create two directories (e.g. one on server, one on laptop)
touch d1/foo.txt # Create an empty file
rsync -r d1/ d2/ # Sync the directories
echo "123" > d2/foo.txt # Now modify the file on d2 (e.g. laptop)
rsync -r d1/ d2/ # Sync again
cat d2/foo.txt # Ooops - foo.txt is empty!

One possible way I experimented with is the following:

- Integrate a rsync server -> laptop in the startup procedure of the laptop
- Never modify a file on the server while working with the laptop
- Integrate a rsync laptop -> server in the shutdown procedure of the laptop

In theory this works, but practically there are cases where you miss the shutdown/startup sync, e.g. when you have no network at startup (e.g. you took your laptop away from home and forgot to sync it), in case you laptop crashes, the network fails during shutdown and numerous other problems. These lead to dangerous situations, e.g. if the rsync laptop->server fails during shutdown, a startup-rsync may overwrite modified files.

After loosing some of my work, I decided to switch to unison, which is a 2-way sync and lets me decide how to resolve syncing problems.

Nevertheless I'm not entirely happy with the situation - if I forget to sync, I have to resolve things manually, moreover the sync takes quite some time.

In my special case, I have a WLAN connection to my server most of the time, so changes could be written immediately. So I'd favour some kind of network file system that has offline capabilities and can handle two-side modifications in some way. I thought about Coda but it seems to be far too complicated and unreliable and I don't know better alternatives.

So I'm still stuck to my Unison solution, which is somehow cumbersome, but works...

Re:rsync

[Znork]

"AFAIK, rsync is only one-way, meaning that it overwrites and eventually deletes files."

rsync has a whole bunch of options that will let you decide behaviour. --update will make it skip files that have newer modify times or you could use --backup to make it make a copy of files instead of overwriting them, etc. Mix and match and run two-way syncs after eachother and you could get close in behaviour to a real two-way sync.

"I thought about Coda but it seems to be far too complicated and unreliable and I don't know better alternatives."

I've played around with Coda, and from what I recall there are two things that make it impractial for 'ordinary' use. The lack of file locking (which causes problems with annoying apps that use it) and the handling of large files (it had to copy the entire file to local cache before unblocking the io calls, ie, dont look at any video files on coda). And so, my original idea of having home directories supporting disconnected operations were shot. It would have worked very well for specific subsets of datastorage, but in the end it was simpler to just sort the data into various structures and deal with syncing on a case by case basis (rsync for some things, plain nfs/autofs for other things, cvs for code or text, etc).

In the end, I think this is one of those problems where it's better to just sit on your arse and wait because the problem of permanent connectivity will be solved before someone figures out how to make a wholly transparent redundant filesystem that seamlessly supports disconnected operation. The whole problem is simply to a certain extent incompatible with the way filesystems usually work.

Re:rsync

[deimtee]

That's strange, n'sync CDs don't have any music on them.

iFolder?

[belly69]

That sounds exactly like what Novell's iFolder is made for:

http://www.ifolder.com/index.php/Home

Re:iFolder?

[Anonymous Coward]

Agreed. I work for a little company with a few hundred on-the-road consultants who keep their lives (gigabytes of data) on their laptops and on desktops at work. The workstations are on when they are there and sometimes even when they're gone, and the laptops are on sporadically. When logged in everything synchronizes once per minute. If changes happen on the laptop they go to the server and, if the workstation, they also go the workstation. The synchronization is bidirectional and happens with the newest versions of the files no matter how many clients. We used to use regular "shares" in windows (AD) but dropped it when we added this technology. It's still available for some purposes but our IT department doesn't even use them anymore when iFolder is available because it's faster, automatic, and seamless.

Re:iFolder?

[freckledp]

I used to work for Novell, traveling two or three times a month. My personal office had several computers and I had multiple laptops that traveled with me. Using either Windows or Linux clients of iFolder, I was able to easily sync files from one machine to another, always ensuring that I had the latest copy of whatever file I needed. It sounds like exactly what you need.

One possible problem: you have to store the information in a folder (which you specify). Only the data in that folder is synced.

HTH

-FreckledP

Re:iFolder?

[killjoe]

>What do you mean if iFolder was mature?

I don't know how mature the novell version is but the open source version is very far from being mature. In fact there hasn't been a stable release in more then two years and nobody knows if or when there will ever be a stable release.

A while ago all the developers on ifolder either quit or were fired and the development was moved to india. Since then the pace of development has slowed down to a crawl and the new developers try to understand the code base and fix bug reports.

Right now you can download something that is beta-ish but I certainly would not trust my mission critical data to it. If you want something that works you are going to have to pull off the trunk and compile it.

Re:iFolder?

[hendersj]

iFolder3 lets you specify whatever folder you want - I sync about 5 or 6 folders and share them with different people in my department.

(And if you're who I believe you are (CC), hey! Drop me a line...)

Unison

[graphicsguy]

I use unison. Why would you need to run it manually every time? It can be run in batch mode. I am mostly using it for live backups these days rather than true bidirectional synchronization, so I could really use rsync and some scripts, but I've gotten pretty comfortable with unison.

my take

[TheRealMindChild]

Man... You are late to the party. People have been struggling with this since the beginning of time (or so it seems). Especially database apps, where they need to work in "detached mode".

I can't give you a flat out solution, because all situations are different. But I can pass on a bit of wisdom. The most important thing for you to do is create business rules for your synchronization. If the data on the server has changed and you made changes offline, who gets priority? You will have three categories of which a file can be... Client changes get priority, Server changes get priority, and Merge files. I would stay away from the last one. If you want to keep things simple, Id go for the "Server changes get priority" approach. In short, if you took an "online" file "offline" and came back, and the server copy has changed since, your offline edits are abandoned. This way, it makes it so heavily edited files have a shorter "check out window" (even if you don't use a checkout system), and forces the person taking the file offline to coordinate with everyone else that may edit this file.

common problem

[ILuvRamen]

When the laptop is reconnected, I want the data to automatically re-sync. The issue is, the data on the server may have changed as well, which needs to propagate back to the laptop.

And there you have the problem with synchronization. There's no mind reader program (yet) so sorry but you're going to have to make up your mind about how to handle it when the server version changed too. Either find a way to merge the files or start making decisions about when they can get modified (ie a checkout system) or if the server's or the laptop's version is always right or if the user gets to choose (bad idea). As for programs, stop looking at famous ones, they suck. That's like using Norton as your antivirus. Find some freeware or open source one that does just what you need and isn't overly complicated

Am I missing something?

[aero2600-5]

From the summary:

"The issue is, the data on the server may have changed as well, which needs to propagate back to the laptop."

So let me get this straight.. You have the old version of the file, somewhere. The new laptop version of file, somewhere. And the new server version of the file, somewhere. And you want the software to decide which to use and copy it to both the server and the laptop?

There are even more issues here, but it kinda sounds like you want some artificial intelligence that you can download.

Aero

Re:Am I missing something?

[sholden]

Have fun trying to merge changes in an executable binary file.

Not seeing the difference between arbitrary files on a disk and files that have been explicitly version controlled is I guess what makes you the hardware guy - does that mean you nail the floorboards down?

Windows might be good for something

[wpanderson]

My Briefcase in Windows 95. It even has a cute ickle briefcase icon.

Somewhat seriously, Offline Files in Win2K/XP is something I've yet to see done well on any other OS.

Re:Windows might be good for something

[arivanov]

Offline most likely derives its origins from Coda which was designed to work for 100MB at most. It seems to inherit all of its problems when the data volumes become big. I have had to support an environment where people casually offlined 3-4GB documentation trees and it was falling over on regular basis.

Further to this, offline files has a number of fairly fundamental bugs in the actual implementation. It records both the IP and the name of the server somewhere when doing the offlining. As a result if the name (but not the drive) or the IP changes your entire offline tree goes south and stays offline. You can neither delete it nor reconnect it and the only way of dealing with this is either surgery to the network (aliasing IP addresses) until you reconnect. The only alternative is to rebuild the affected laptops from scratch.

Re:Windows might be good for something

[dos]

It records both the IP and the name of the server somewhere when doing the offlining. As a result if the name (but not the drive) or the IP changes your entire offline tree goes south and stays offline. Go download csccmd 1.1 from Microsoft.

csccmd /moveshare will take care of this.

Re:Windows might be good for something

[juanhf]

windows' built in offline files is great; i only started using it in the last year or two and i feel like i have come from hiding and into the light.

the system is configurable through group policy which makes it easy to setup the system throughout an enterprise.

here are some links:

how to use offline folders http://support.microsoft.com/kb/307853

in your case, there is a way to fix offline folder problems (when and if they occur) have a look at:

how to re-initialize offlines files cache: http://support.microsoft.com/kb/230738/en-us

last but not least, here is a link to group policy for offline folders: http://technet2.microsoft.com/windowsserver/en/lib rary/9dba5df2-0359-4fa4-bdcf-dd6ae5ca345e1033.mspx ?mfr=true

Coda

[norkakn]

http://www.coda.cs.cmu.edu/

Re:Coda

[gouldtj]

I've always wanted Coda to work for this, but I haven't ever gotten it working. My current thinking is that I'd need to set up a server on my laptop, and then have the client talk to the local server. Then the two servers could sync.

Does anyone have any information or case studies on how to make this work for a small network? Easy conversion tools? It seems like the ideal solution to me, but getting it to work seems difficult.

--Ted

Re:Coda

[EvanED]

My current thinking is that I'd need to set up a server on my laptop, and then have the client talk to the local server.

I haven't actually used Coda, though I'm planning on it for a small network myself, because this is exactly what it was designed to do. But why would you need the server on the laptop? All you should need is a client. Have you tried it that way and it didn't work or something?

I do hear it's a pain to set up though.

Re:Coda

[wildjim]

Funnily enough, I've been working on exactly this over the weekend. Unfortunately, the docs are terrible.
Some of the Wiki info suggests that things have improved, but I'm discovering a decent-sized client cache (10Gb) so that I can offline most of what I'd use has horrendous occaisional slow-downs and pauses.
I'm planning on testing a local/client server and a client with the RVM turned-off this week, but I'm not keen on the size that the RVM file(s) will have to get to.
Previous comments in here suggesting it's not really designed for modern data-sets (gigs rather than megs) are starting to look as if that's true... Other than that, it actually looks like a reasonably good design!

Re:Subversion

[Iron Condor]

At the risk of saying something stupid or blasphemous: why offer something that requires "writing some scripts"?

If the OP wanted to "write some scripts" s/h/it could have done all the neccessary work with a couple foreach...cp...end. Or, hey, rsync.

I am suspecting the OP is wondering whether there isn't something out there that "just kinda works" and only needs intervvention in case of a conflict.

Knowing well that this will definitely be considered blasphemy: I've been using Window's "briefcase" system since Win98. It does "kinda work". Most of the time. And requires work when there's a conflict. Which appears to be what the OP is looking for. Given that the OP doesn't seem to want to just go that route, the question appears pertinent what s/h/it is looking for that Mr. Gates briefcases can't/won't do...

Windows & Make Available Offline

[goofy183]

I'll likely get buried but here it goes:

In Windows you can mark a folder on a network share as "Available Offline". Windows will copy all of the files to the local HD and if the server isn't available just work with the local copies. When the server is detected Windows will automatically sync the files and pop-up asking the user about conflicts (keep local / keep remote). When connected writes automatically go to both the local copy and the server.

One of the few places that Windows has right and I haven't found a Linux or OS X solution for that is nearly as nice.

Re:Windows & Make Available Offline

[Techman83]

A great solution till it breaks... believe me it does break and when it does be prepared for heartache. There are ways to recover it, but I think it assumes to much and the potential to screw up is a big risk. There were several users at my place of employment that found out this the hard way and now we ban the usage of it. It's not so much finding the best tool, but managing the process overall and how to do that.. Well we are still in the process of developing that one!

Re:Windows & Make Available Offline

[knitterb]

Works well for me too. Sure, every now and then you get a mishap or a mistaken overwrite, but that's what [client and server] backups are for, right?

I use it with my wife for our financial data. She syncs, makes changes, then next time I connect I can choose to use the server version or my version. Since there is no version control, you have to communicate. Then again, with the way version control works, if you end up merging a lot, perhaps too many people are working on the same problem anyhow.

In the end it works well.

Foldershare

[Offtopic]

I've been using Foldershare for several months now to synchronize several folders on three different machines. It has worked well so far and it is free. It's available at: https://www.foldershare.com/

OS X Client & Server does a good job with this

[phillymjs]

I'm not exactly sure what Apple uses under the hood to accomplish it. I don't think it's rsync, because I've fooled with the rsync built into OS X and I get errors frequently, but their home syncing works great.

When you have a mobile user account (i.e. a network account with a local copy of the home folder on the workstation), it will sync every so often (frequency and exactly what is synced/skipped can be configured on the server end, and the user can kick it off manually from the client end). To the best of my knowledge, the sync is bidirectional, so if you log into another machine with a mobile account and modify the server copy, the changes will be reflected on the mobile copy at next sync. It makes my life easier because if a laptop user's machine gets lost, stolen, damaged, or destroyed, we've automatically got a backup copy of the data on it up to the last time it was synced.

In the event of conflicts, the user is presented with a dialog asking which version to keep, including file size and modification date.

Note that I'm not suggesting you throw out your existing hardware and buy Macs to get this feature, but maybe look into exactly how it's done on the Mac and see if you can duplicate it on your systems.

~Philly

In OSX, portable home directories

[shamborfosi]

I have OSX laptops using portable home directories to do exactly what you are asking for.. a network home directory that is automagically sync'd to my laptop (thus making it portable). It works both ways, and I'm definitely happy with it. I'm not sure which OS you're using though. I wrote about how to do it in an article: Full Stack: Portable Home Directory over NFS on OSX authenticated via OpenLDAP on Debian Linux if you're interested. I also just got everything to work over AFP to an OSX server running open directory as well.. but haven't had time to write it up yet (btw, a lot fewer steps).

Try coda

[blymn]

Have a look at http://coda.cs.cmu.edu/ This is a disconnectable file system. It could be what you are looking for. Certainly, that is what I use for doing the same thing.

Unison

[sgyver]

Maybe a two-way rsync tool made just for this purpose?
You might have to do A-B, A-C, A-B type syncs for more than 2 paths, unless you stick to a hub/spoke or cascading distribution model.
Not all conflicts are automatically resolved, by default.

http://www.cis.upenn.edu/~bcpierce/unison/

Good luck.

commercial products.

[deviator]

Offline Folders on a Windows client connected to a Windows server work reasonably well but sometimes get screwed up.

Novell's iFolder is a very interesting alternative... runs on Linux/Apache/Java stack & only transmits changed blocks over an SSL connection.

Other things worth looking into include Microsoft Groove--let's you synchronize an entire workspace with yourself on other computers or other people - and is relatively network & environment-independent (though Windows only)

Synchronization Woes

[JWSmythe]

A few people hit this one pretty well. rsync (and probably rsyncd).

    The more complex problem has been thrown at me a few times. What if it's not just one person?

    Say you have a repository of data that a dozen people may be working in. When they're all network connected, they're all dealing with the same file pool. When they take their off-line copies with them (unplugged laptops on vacation), they all make changes to the same files. Maybe mine is a one line change. Maybe one guy copy&pasted the first 3 chapters from War And Peace into a comment somewhere in the middle. Maybe another developer did some very intellectual looking changes but hosed some major functionality.

    When you start putting machines back on the network, who is right? The 6 guys who did real work are obviously right(ish), but they all made different changes. The very last change will end up being someone's 3 year old kid who was pounding on the keyboard right before daddy shut down the laptop, saving the new changes. Probably the last is the most recent, and right by most methods.

    It's not a pretty picture, and requires some intelligence to sort out the mess.

    The only "good" resolution I've found is to give logical authority to the changes. Bob is in charge of development. Any changes going into the development or production tree must clear him. He should be able to recognize that the 6 guys made changes, and diff them to come up with the common changes. The 3 chapters of war and peace go by the way side. And the guy with the 3 year old "developer" gets reprimanded.

    In the end, a good revision system and good backups are needed too. Something will slip through the cracks, and you'll need to roll back to something you hope is good.

    I take control over whatever I'm working on, so if I know I'll be working offline, I'll scp the data to my laptop, work on it on the road, and scp my changes up to the server when I'm done. Anyone else who may have worked in my project space in the duration should have known better. :)

Coda, AFS, InterMezzo

[RAMMS EIN]

There have been some efforts in the area of networked filesystems with disconnected operations. I remember checking out AFS, Coda, and InterMezzo years ago. At the time, I found something wrong with each of them, but they may have improved since then. Of the three, I think Coda is your best bet.

you already solved your problem

[coaxial]

Simply instally unison or rsync or whatever and have the job kick off with whereami for linux (you'll have to find the main page yourself) or marco polo for macs.

Re:Subversion

[aldheorte]

"s/h/it"

You may want to reevaluate your approach to political correctness.

SyncBackSE

[__aalmrb3802]

If you're running Windows, I would recommend SyncBackSE (http://www.2brightsparks.com/syncback/sbse.html), which I expect you should be able to setup to do exactly what you asked.

OpenAFS

[sid77]

As said before there're many choices, each ones with its own pros and cons, so I'll throw this one in: OpenAFS.

As read from the main page:

What is AFS?

AFS is a distributed filesystem product, pioneered at Carnegie Mellon University and supported and developed as a product by Transarc Corporation (now IBM Pittsburgh Labs). It offers a client-server architecture for federated file sharing and replicated read-only content distribution, providing location independence, scalability, security, and transparent migration capabilities. AFS is available for a broad range of heterogeneous systems including UNIX, Linux, MacOS X, and Microsoft Windows
Hope this helps, ciao

Re:common refrain

[oatworm]

Not that it matters, but since you asked...

Photoshop -> GIMP
Avid -> LIVES - Note: I am not a video editor and have no idea if this program is any good.
Quicken -> GNUCash, among others.

I guess what I'm saying is that, based on your definition of "silly", there's quite a bit of silliness going on in the world today. *grin*

Unison, Rsync & NTP

[Colin Smith]

Unison can be scripted, added to a login script. As can rsync on windows. Alternatively you can add a polling batch file which wakes up every so often and checks to see if the server lives. (Yes, even on Windows)

Rsync can sync in both directions, but you decide one of the sides is the master and sync that one first, in the case of conflicts the master rules. It isn't possible to choose on a file by file basis at sync time as you can with Unison.

Oh, and NTP is absolutely vital when doing any synchronisation.

Basically. Either you do it manually and manage conflicts at sync time, or you do it automatically and define one of the sides as a master in the case of conflict. There's really no way round this, software just isn't sophisticated enough to decide what you're thinking.

The truth is that filesystem syncing isn't ideal for a very dynamically updated file system. It is best used on fairly static filesystems or one way syncing. Documentation, backups and the like.

Re:Unison, Rsync & NTP

[ajs318]

DEC had all this sorted out back in the days of the PDP-11! Filenames would get a version number appended (such as LOGIN.COM;12) and you could specify how many versions to keep hanging around. Writing a file without specifying a version number would create a new version, reading a file without specifying a version number would use the latest version.

Re:Unison, Rsync & NTP

[Colin Smith]

Sure there is another way: newest file wins. But this means that any number of intermediate edits by arbitrary numbers of people will simply and silently be removed if someone updates an obsolete version between syncs.

nevertheless I couldn't find software that would support this, thus had to write it by myself... Eh? Rsync supports it. rsync -u ...

Re:Subversion is for stupid and ugly people

[cduffy]

git's chunk-based rename handling is interesting, but bzr's directory-level handling is closer to what most users expect. (Does the git behavior make more sense for the kernel source tree? Sure! Does it make more sense for Joe Blow's home directory? I'd need some convincing there).

Out here in the Real World, folks setting up revision control systems need to count "stupid people" (read: artists and web designers who are too busy making art or designing web pages to care about revision control except inasmuch as it's a way to back up and distribute their work) among their customers. For a great many cases, subversion is Good Enough, and it has excellent Windows support, integration with just about every IDE under the sun, TortoiseSVN and other nice pretty hand-holdy tools available which simply aren't ubiquitous among SCMs written with hardcore users in mind (seemingly to the exclusion of those that aren't). SVN isn't distributed, which sucks. SVN has an ugly hack of an excuse for a rename handling algorithm, which sucks. SVN is slow as molasses compared to some of its competition and lacks merge tracking (and thus history-sensitive merging) and has a gawdawful working tree library and sucks in any number of other ways -- but it is a compelling replacement to CVS, and sometimes that's what the customer needs, no matter what shiny happy features ${YOUR_FAVORITE_SCM} may have and no matter how many ways SVN manages to annoy the power user.

And trust me, I learned this one the hard way.

As for the 4NT copy suggestion, the whole bidirectionality and rename handling arguments come into play.

Re:Subversion

[Godman]

I sat here for about 10 minutes before realizing that s/h/it wasn't a regex joke and why it was actually funny... :-/

Will there be a Linux client?

[STFS]

subject says it all.

Re:Subversion is for stupid and ugly people

[rawler]

There's a reason why SVN don't distribute well. It simply don't branch well.

And in branching, most of the GUI-users just don't get a clue and practically eliminates any chance there was for decent branching/merging.

SVN/Tortoise are good for one thing, snapshotting, and that should better be handled by the filesystem itself anyways. (Why are filesystem snapshotting STILL not mainstream, btw?)