In the beginning concepts part of the manual, it says that ddrescue will use the largest size (largest 64-bit integer) if it doesn't know the size. >From what I can tell, this seems to happen all the time on MacOS. Diskutil doesn't have an issue, but ddrescue does. E.g.:
Device Identifier: disk4s1 Device Node: /dev/disk4s1 Whole: No Part of Whole: disk4 Volume Name: Mounted: No Partition Type: Windows_NTFS File System Personality: UFSD_NTFS Type (Bundle): ufsd_NTFS Name (User Visible): Microsoft NTFS OS Can Be Installed: No Media Type: Generic Protocol: USB SMART Status: Not Supported Volume UUID: 09905948-1B82-439D-9614-8FAAB029527F Partition Offset: 32256 Bytes (63 512-Byte-Device-Blocks) Disk Size: 40.0 GB (40007729664 Bytes) (exactly 78140097 512-Byte-Units) Device Block Size: 512 Bytes Volume Total Space: 0 B (0 Bytes) (exactly 0 512-Byte-Units) Volume Free Space: 0 B (0 Bytes) (exactly 0 512-Byte-Units) Media OS Use Only: No Media Read-Only: No Volume Read-Only: Not applicable (not mounted) Device Location: External Removable Media: Fixed Solid State: Info not available When attempting to image this disk, ddrescue reports the size as 9PB. (sizes limited to domain from 0 B to 40_007_729_664 B of 9_223_372_036_854_775_807 B) Again, this is not unique to this particular disk. This utility routinely can't figure out the device sizes. Maybe for MacOS include a helper utility that just asks diskutil how big the size is if it's deciding to use the maximum 64-bit integer. (The line above was generated when adding the argument "-s 40G".) *— Eric C. Berlin, MIS.* *NOTE: If you send me an email and do not get a reply in two business days, please phone me. I get a lot of emails and may have missed your message.* ECJB Computer Services, LLC [email protected] Skype: ecjb1969 ------------------------------ 609-641-3141 <http://voice.google.com/calls?a=nc,%2B16096413141> <http://voice.google.com/calls?a=nc,%2B16096413141>(Voice) EASTERN TIME 609-401-9290 (Cell) 609-641-8241 <http://voice.google.com/calls?a=nc,%2B16096418241> <http://voice.google.com/calls?a=nc,%2B16096418241>(fax) 2528 Tilton Rd, Trlr 97 Egg Harbor Twp, NJ 08234-1649 “If a million people believe in a dumb idea, it’s still a dumb idea.” — ECJB. “I am who I say that I am, which is defined by what I believe, which is how I try to act.” — ECJB. ecjb.net <http://www.ecjb.net/> — Personal site ecjb.org <http://www.ecjb.org/> — Business site *Google Profile:* This profile links to my various pages. We use Angie's List to assess whether we're doing a good job keeping valued customers like you happy. Please visit AngiesList.com/Review/8064529 <http://angieslist.com/Review/8064529> to grade our quality of work and customer service. HomeAdvisor owns Angie's List now, and you can see reviews here: https://www.homeadvisor.com/rated.ECJBComputerServices.67288824.html. My Google business page and reviews can be found here: https://g.page/ecjb-computer-services-llc.
