Disk Writer Error Message "Failed to Write MBR (5) (1)"

Anything and everything to do with DCP-o-matic.
bleedingkanzas
Posts: 2
Joined: Mon Sep 15, 2025 3:35 am

Disk Writer Error Message "Failed to Write MBR (5) (1)"

Post by bleedingkanzas »

Hi everyone,
I'm new to use the DCP-o-matic software. I'm a manager of a small theater and I'm trying to make a DCP version of trailer for an upcoming special screening we're doing. I tried to use the Disk Writer software to make sure the external hard drive I'm using will be correctly formatted and such to read the files. I just tried using it and it gave me this error message "Failed to Write MBR (5) (1)". I'm curious if anyone else has encountered this and what I can do to fix this.

Thanks in advance for your assistance!
carl
Site Admin
Posts: 2997
Joined: Thu Nov 14, 2013 2:53 pm

Re: Disk Writer Error Message "Failed to Write MBR (5) (1)"

Post by carl »

Hi, this is a known bug where DCP-o-matic doesn't manage to get the right macOS permissions. Please can you try this workaround:

https://dcpomatic.com/faq/27

Let us know if that doesn't fix it.
bleedingkanzas
Posts: 2
Joined: Mon Sep 15, 2025 3:35 am

Re: Disk Writer Error Message "Failed to Write MBR (5) (1)"

Post by bleedingkanzas »

Those instructions did fix the initial issue. However, I then ended up getting this error message after I got the program to process the DCP file I was working on: "boost::filesystem::directory_iterator::construct: No such file or directory [system: 2]"
I tried restarting the program and realized that my laptop was no longer recognizing the external hard drive I was using and I had to wipe the drive and lost my progress. Thankfully I didn't have anything else on there since I just got it yesterday for this purpose. But yeah, I'm curious where I went wrong and how I can fix/avoid it going forward.
Last edited by bleedingkanzas on Sat Apr 18, 2026 8:42 pm, edited 1 time in total.
carl
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Joined: Thu Nov 14, 2013 2:53 pm

Re: Disk Writer Error Message "Failed to Write MBR (5) (1)"

Post by carl »

So this is the external drive that you are copying the DCP onto? You know that the DCP-o-matic Disk Writer will wipe the drive that you ask it to use?
bleedingkanzas
Posts: 2
Joined: Mon Sep 15, 2025 3:35 am

Re: Disk Writer Error Message "Failed to Write MBR (5) (1)"

Post by bleedingkanzas »

Yeah, I was aware of that. But, I had to go back and wipe the external hard drive again because my laptop was no longer recognizing the external hard drive after I got that other error message on Disk Writer.
carl
Site Admin
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Joined: Thu Nov 14, 2013 2:53 pm

Re: Disk Writer Error Message "Failed to Write MBR (5) (1)"

Post by carl »

Do you mean macOS was not recognising it, or the disk writer was not recognising it?

Does this ""boost::filesystem::directory_iterator::construct: No such file or directory [system: 2]" happen every time you try to write the DCP?
IoannisSyrogiannis
Posts: 377
Joined: Mon Nov 13, 2017 8:40 pm
Location: Iceland

Re: Disk Writer Error Message "Failed to Write MBR (5) (1)"

Post by IoannisSyrogiannis »

bleedingkanzas wrote: Sat Apr 18, 2026 8:39 pm [...]
I tried restarting the program and realized that my laptop was no longer recognizing the external hard drive I was using [...]
I might be barking under the wrong tree, here. Yet, please let me understand, was your computer expected to recognize the MBR, EXT2/3 drive and partition?

(O.K. I see I was writing simultaneously with Carl, here.)
theirongiant
Posts: 9
Joined: Mon Jul 06, 2026 1:03 am

Re: Disk Writer Error Message "Failed to Write MBR (5) (1)"

Post by theirongiant »

FWIW, I was able to format an external drive after following these instructions to allow Full Disk Access for the disk writer executable in the /Library/Application Support/com.dcpomatic/ folder.

Currently, pressing "Refresh" does not work as expected. The app keeps complaining that the disk is "no longer available." The workaround is to quit and relaunch the Disk Writer app.
Carsten
Posts: 3114
Joined: Tue Apr 15, 2014 9:11 pm
Location: Germany

Re: Disk Writer Error Message "Failed to Write MBR (5) (1)"

Post by Carsten »

BTW - if you are creating discs for your own cinema, it is perfectly okay to use NTFS.

As a matter of fact, all cinema servers accept NTFS discs for ingest. It's just some festivals or archives that stick strictly to the official ext2/ext3 requirement.


In order to transfer just a trailer, using ext2/3 is overkill. You may even be able to use a standard USB-Flashdrive (as long as you format it to FAT32 or NTFS).

From your last post, I assume you use a Mac. NTFS write support is not native in Mac OS, I use Tuxera NTFS in Mac OS X. As a quick turnaround, you may even use FAT32 (as longs as the trailers video MXF is not larger than 4GB).

Also: https://www.youtube.com/watch?v=e9x-_n-ZQFY&t=7s
theirongiant
Posts: 9
Joined: Mon Jul 06, 2026 1:03 am

Re: Disk Writer Error Message "Failed to Write MBR (5) (1)"

Post by theirongiant »

Carsten wrote: Mon Jul 06, 2026 6:36 pm BTW - if you are creating discs for your own cinema, it is perfectly okay to use NTFS.

As a matter of fact, all cinema servers accept NTFS discs for ingest. It's just some festivals or archives that stick strictly to the official ext2/ext3 requirement.


In order to transfer just a trailer, using ext2/3 is overkill. You may even be able to use a standard USB-Flashdrive (as long as you format it to FAT32 or NTFS).

From your last post, I assume you use a Mac. NTFS write support is not native in Mac OS, I use Tuxera NTFS in Mac OS X. As a quick turnaround, you may even use FAT32 (as longs as the trailers video MXF is not larger than 4GB).

Also: https://www.youtube.com/watch?v=e9x-_n-ZQFY&t=7s
Thanks. Yes, I use a Mac. I have a PC available and could format an external drive as NTFS and copy the DCP folders to it. I tested the app with a SanDisk USB3.0 flash drive. It worked fine, even if it was a little slow — write @ 50MB/sec, read @ 125MB/sec — but this is acceptable for ingesting trailers, or highlight reels under 10 minutes in length.

After using DCP-o-Matic's disk writer, I checked the disk layout on a Linux computer (my Raspberry Pi). It appears that the DCPs are just folders at the root of the drive? Is that the only requirement?

I can't wait to get past the minimum post/comment count on this forum so the moderators don't have to keep manually approving my comments.