If you see the message
iPartition was unable to get write access to the device “SOME DEVICE NAME” (disk0). This may mean the device is write protected, that you do not have permission to access it, or that it is in use by something else.
It means that iPartition was unable to open the specified disk for writing. This could be because:
- The disk in question is read-only (or has a write-protect switch that is enabled). SD cards typically have write protect switches, as do some USB sticks and various other types of removable media.
- When prompted for a username and password, you clicked “Cancel”. Some disks are protected by Mac OS X and cannot be directly accessed without authentication.
- Another program is using the disk. This might be because you opened a file on the disk in a program you started, or it could be because you used Terminal and set the current directory in a terminal window to that disk. It could also be because a background task you didn’t start is using the disk.
In the case of background tasks that might be using a disk, the following are particularly troublesome:
- Spotlight’s indexer. You may have to add the disk to the “Privacy” list in Spotlight’s preference pane in System Preferences to persuade the indexer to leave the disk alone.
- Anti-virus software. On-demand anti-virus scanners typically go and examine disks when they are attached to the machine without being prompted to do so; they may also open and examine files on those disks. Disabling these kinds of programs may help.
- Core Storage. This is used to implement Fusion Drives and File Vault 2; it is also used by default on Yosemite or higher. If you have a Fusion Drive, iPartition probably isn’t going to be all that useful, because you have to use Core Storage and current versions of iPartition can’t resize Core Storage volumes. If you are using File Vault 2, you can simply turn it off (and wait for the disk to decrypt). If you are using neither of those things, but your disk is still showing as Core Storage in iPartition, you might need to follow the instructions in this support article to convert the disk back to a normal one before using iPartition.
In particular, if you get the message
iPartition was unable to get write access to the device “Apple SSD SM0256F” (disk0). This may mean the device is write protected, that you do not have permission to access it, or that it is in use by something else.
it is very likely the case that you are trying to manipulate a disk with one or more active Core Storage partitions, quite possibly a Fusion Drive. Please see this support article if you are in that situation.