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Do these have the same effect when the drive has only one big partition?

udisks --unmount /dev/sdb

udisks --unmount /dev/sdb1
H2ONaCl
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2 Answers2

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Well --- it depends. Basically, it depends on if the device is partitioned or not (used whole). If it has just one big partition, it's partitioned anyway.

I have a device (a Garmin GPS) that looks like an unpartioned disk, look (from the command mount which shows the mounted devices): 

/dev/sdc on /media/romano/GARMIN type vfat (rw,nosuid,nodev,uid=1153,gid=1001,shortname=mixed,dmask=0077,utf8=1,showexec,flush,uhelper=udisks2)

so this disk needs to be unmounted with umount /dev/sdc.

Notice however that this is a bad thing in general, stemming from the age of floppy disks --- if you still have one of those, they were mostly unpartitioned. Devices should be partitioned, even if they have just one big partition. Otherwise a lot of things expecting it will not automount the thing --- it happens randomly on Trusty with my Garmin, too.

A normal disk when mounted look like this: 

/dev/sdd1 on /media/romano/I2MTC15_RG type vfat (rw,nosuid,nodev,uid=1153,gid=1001,shortname=mixed,dmask=0077,utf8=1,showexec,flush,uhelper=udisks2)

so it has to be unmounted with umount /dev/sdd1.

Anyway, getting it wrong will just throw an error... 

[romano:~] % umount /dev/sdd 
umount: /dev/sdd is not mounted (according to mtab)
Rmano
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You can unmount only a partition, not a disk. So it is /dev/sdb1.

You can do it by

umount /dev/sdb1

too.

Pilot6
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    That's not really true. There's nothing to stop you from doing mkfs /dev/sdb (don't try if there is anything important on the disk) and then you'll be able to mount /dev/sdb and unmount it too. People usually use partitions for filesystems, but the whole disk device can be used too. It's more common on "small" devices like flash drives, CD-R or DVD-R, etc. – Nate Eldredge Oct 03 '15 at 20:46
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    @NateEldredge Well --- if you mkfs the whole disk you will not have any partition left ;-) --- so this answer is tersely correct for a device "with one big partition" as the OP is asking. – Rmano Oct 04 '15 at 08:35