When I plugin a usb-drive or open dmg-archives they don't appear under the 'Devices' section in the sidebar of the Finder anymore.
The drives are there when I check with 'Disk Utility', they appear on the Desktop and I can browse the files if I go to /Volumes.
I have 'Hard disks' and 'External disks' checked in the Finder preferences -> Sidebar tab.
Any ideas on how to get them to show up in the sidebar?
I'm using MacOS Lion 10.7.5.
In your Finder sidebar, can you see your internal hard drive listed under Devices? If you hover over Devices you should see either Show or Hide just to the right of it, perhaps it's set to hidden?
In my case it was a faulty usb drive. I still don't see the hard drive in "Finder" sidebar, but I'm figuring that's just the way it is with Lion? I adjusted the Finder Preferences so I can now see the HD and other drives on my desktop...
i am on mojave. nothing of the above worked for me. in order to have the disk images appear in the sidebar when opening a DMG file, i deleted the preferences of finder (~/Library/Preferences/com.apple.finder.plist) and sidebar (same folder, file com.apple.sidebarlists.plist). please note that i had various com.apple.finder.plist files, with the base-name completed by random alphanumeric sequences: com.apple.finder.plist.QNHART6 and the like. i had to delete of all of these com.apple.finder.plist files. after what the behavior was again that when clicking to open a DMG file, the disk image appears in the sidebar.