Want to sync 2 external USB drives, what should I use

[sgtdetritus]

Hi everyone.  I have 2 external USB 1TB hard drives that started out the same, but have been connected to 2 different machines and now have different contents.  Is there a Utility that will look at both drives and pretty much make them mirror images without losing data on either drive.  I would only need to do this occasionally as neither drive holds critical data, mostly just music, pictures and video.
Thanks for your help

[JALU]

Hello sgtdetritus,
I might use rsync command (terminal).  Take a look at man:rsync page using konqueror for details.  
The following option available in rsync may may be useful for your purpose.

-c, --checksum
 This changes the way rsync checks if the files have been changed and are in need of a transfer. Without this option, rsync uses a "quick check" that (by default) checks if each file’s size and time of last modification match between the sender and receiver. This option changes this to compare a 128-bit checksum for each file that has a matching size. Generating the checksums means that both sides will expend a lot of disk I/O reading all the data in the files in the transfer (and this is prior to any reading that will be done to transfer changed files), so this can slow things down significantly.
 The sending side generates its checksums while it is doing the file-system scan that builds the list of the available files. The receiver generates its checksums when it is scanning for changed files, and will checksum any file that has the same size as the corresponding sender’s file: files with either a changed size or a changed checksum are selected for transfer.
 Note that rsync always verifies that each transferred file was correctly reconstructed on the receiving side by checking a whole-file checksum that is generated as the file is transferred, but that automatic after-the-transfer verification has nothing to do with this option’s before-the-transfer "Does this file need to be updated?" check.
 For protocol 30 and beyond (first supported in 3.0.0), the checksum used is MD5. For older protocols, the checksum used is MD4.

[µT6]

if i remember correctly, there is a graphical tool that interacts with rsync, grsync maybe?

what i'm not sure to understand is that if you want to have the same content on both hard disks or one must receive the changes of the other?

if i understand well, rsync does what you want but on one direction only, moving from a to b, but you need a and b to be equal?

[OldGuy]

Wouldn't LuckyBackup do the job.  I use it to backup/sync between disks using KDE.

[sgtdetritus]

I want both drives to be the same.  One is a media server that is dedicated to the TV i my living room.  It does not have network access because that is not really necessary.  The other will serve as a media server to the rest of the devices in the house.  Occasionally I will use the non network connected machine to make backups of DVDs, but I use other machines to pull photos off of our digital cameras and to download music and podcasts and to move them on to MP3 players and tablets.  The positioning of the USB ports on the Media Machine makes it impractical to hold and distribute music, while the other machines lack the horsepower to do much more than one thing at a time (I'm cheap and I am using mostly old hardware like refurbished laptops.)  So I have a video library growing on on one drive, while music and photos are growing on the other.  That is why I want them in sync without losing anything from one or the other.

[µT6]

it sounds like that you could benefit from having a local network covering both machines, wired or wireless so you can avoid the time it takes to rsync both units, also avoid plugging and unplugging things, i have let drop my external drive so many times, i don't trust on it anymore

[YouCanToo]

mirrordir sounds like what you want, it is in synaptic

[sgtdetritus]

Thanks for all your help folks.  I may play with them all.  A network covering them all would be ideal, but right now the living room movie machine does not have wireless and it is too far away from the router to have a hard line (and I'm not inclined to run a cable up the wall and through the ceiling at this point   )  I admit I'm trying to do all of this on the cheap, so physically picking up a drive and walking it over to another machine to do the sync is probably going to be the simplest solution.
Thanks again.  I'll post with success and what I did so if anyone else has a similar problem it could be of some help.

[wayne1932]

I think Krusader can do this too.  Twin pane file manager and you can compare and synchronize the two.

[agmg]

I use Synkron to sync my local files with the ones on my external drive.
It's an easy to use GUI for Rsync. You should check it out.

[Roc4fun]

Another vote for grsync; gui for rsync. 

[The Chief]

I do that exact thing, but using LuckyBackup (another gui for rsync).  I have set it up to not delete from the destination anything on the source.  But once you get both drives identical, you can set it up  to "clone" the drives, that way anything you do on one shows up on the other (add, delete, modify).

[µT6]

i was thinking on a similar procedure, i believe that it can't be done on one single step, or maybe there is a tool doing it we don't know we have?

another option would be to copy everything from one disc to the other and then the other, copy it to the first one, this process shouldn't take too much time, if not much changes happened

still, it is a bit if a dangerous task, because you don't have a central hard disk, so you don't have a plan b if one of the disks fails while copying, perhaps keep a copy of everything on your home partition could help, if there is space for it