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Just this morning, I accidentally created a hdd filesystem without a partition table. I didn't even know it was possible but it happened. Now the issue is to undo it or leave it alone.

For this particular case, I don't want multiple partitions so having no partition table is no problem for me. Indeed, in terms of sysadmin, it's actually convenient. But I don't know if there is any loss of functionality with linux. And I posting to get some guidance on that.

What functionality (other than adding and resizing partitions) am I loosing by not having a partition table. What about portability or compatibility with future system upgrades (staying within linux)? How about interoperability between Linux, Windows and OS X?

marked as duplicate by Gilles, Ramesh, G-Man, cuonglm, dhag May 29 '15 at 2:18

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Linux itself mostly won't care. A few things won't be possible (e.g., installing a bootloader such as GRUB on the drive), but it sounds like that isn't an issue. Some software (udisks, for example) might fail to see it as a mountable filesystem, so it might work less well in desktop GUIs.

If you attach this to a different OS, I'd expect both Mac OS and Windows to offer to create a partition table (read: damage or destroy your data). You probably can get it mounted on either (presuming they support the FS), but the GUIs will not do it. At least not without stunts.

The next sysadmin—or quite possibly you, six months down the road—will care. You've created something weird. The administrator will run fdisk -l trying to find what's on the disk, or how large it is, whatever. Maybe it's been connected to a different machine, or the OS had to be reinstalled, or something bad happened and he/she is trying to recover data, whatever. He/she will get back confusing messages about there being no recognized partition table or, depending on the FS, the first few sectors are intentionally unused—so fdisk will just say its a blank disk! Or maybe instead of fdisk -l, just fdisk followed by p, which will happily show a new, empty partition table.

Will an experienced sysadmin, if thinking straight, manage to figure out what's going on? Yes, he or she should. (Will it take extra time, delaying whatever task needed accomplishing? Yes.)

But will a less experienced sysadmin, or a sysadmin under stress manage to figure it out? Well, I'll point out you didn't know it was even possible, you're surely not alone.

If you decide to keep it this way, please document it somewhere that'll be available and noticed, even if the system it's part of dies. For example, if this is an external drive, you might securely attach a note (a piece of paper) to the drive.

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You're not losing much within Linux - having a whole-disk device as the backing store for a filesystem pretty much just works. You probably won't be able to move the disk to another OS like Windows or Mac OS X, but that's more due to the filesystem not the fact that you're using the whole disk device. The OS interoperating with other OSes shouldn't be affected at all.

Overall, if it's working for you now, I'd leave it alone unless you really want to redo it and create a partition on the disk.

  • I understand that filesystems are not very interoperable, but I guess there are methods to fix that. In which case, is a table-less HDD still accessible, in Windows for example? – codechimp May 28 '15 at 17:07
  • I don't see why it wouldn't be - but then again, if the filesystem is such that Windows can't read it, why are you concerned about the disk behind said filesystem? It (the disk readbaility) has become a moot point because of the filesystem incompatibility. – John May 28 '15 at 17:14

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