The other common error with disk images is that, although their checksums match, the file system within the virtual volume is damaged, and cannot be mounted.įile systems are not routinely checked in all disk images, only those which have a quarantine flag attached and have not already passed an fsck check are put through the process.
If it failed, then that xattr won’t be present, but there will be one with a type name starting :kMDLabel_ to record the checksum failure. If the disk image has passed the checksum check, there will be an extended attribute of type recording that event.
MY .DMG FILE WON'T OPEN FREE
If you’re unsure whether the cause of your problems is a checksum error, look at the disk image using xattred, my free extended attribute editor. dev/disk4s2 Apple_HFS /Volumes/Packages 1.2.2 You should then see a listing of each of the partitions mounted by macOS, such as
MY .DMG FILE WON'T OPEN FULL
Where filename.dmg is the full name of the disk image file. Hdiutil attach filename.dmg -ignorebadchecksums When you’re ready to proceed, open Terminal and type in a command like Before going any further, save all open documents and batten down your Mac’s hatches in case mounting the damaged disk image causes a kernel panic, which it could. If you cannot obtain another copy, and have to get the best out of the disk image that you have, you can force it to be mounted regardless of the checksum issue. If that is an option, then it is the best one. This normally means that the disk image has been damaged, and you should obtain a fresh one. The error message shown above is typically seen when the checksums do not tally. If there’s no current checksum stored in an extended attribute, macOS calculates a new one, compares it against the checksum given in the disk image, and – if they tally – saves the checksum in an extended attribute of type. This explains why mounting a disk image for the first time usually displays a progress dialog while the checksum is checked, but the next time the image normally mounts more quickly. If it finds an extended attribute of type which contains a more recent checksum than the timestamp on the disk image, it accepts that rather than calculating it afresh. Note that this doesn’t apply to read/write disk images, as they don’t store checksums.Ĭalculating the checksum takes a while, so before doing that, macOS looks to see if it has already been done. When you open and mount it, macOS checks that checksum. If the disk image is read-only (as are most installers and apps supplied on disk images) or compressed, when it’s saved it includes a checksum of its entire contents. Before it will offer you the contents of that virtual volume, macOS puts it through some basic checks.
MY .DMG FILE WON'T OPEN HOW TO
To know how to resolve this, you need to understand what happens when your Mac tries to mount that disk image.Ī disk image is just a file that macOS opens and mounts as if the data contained within it were stored on a disk volume.
Worse still, the image hasn’t been mounted, and repeating the action doesn’t help. Let’s say you wanted some files which are stored in an old disk image, so you double-click the image to mount it, and see an error message. Disk images are normally both robust and reliable, but every once in a while they can cause problems.
0 kommentar(er)
