On Sunday 11 February 2018 12:35:54 Thomas Schmitt wrote: > Hi, > > Gene Heskett wrote: > > The real problem is of coarse that there has not ever been 2 > > identical sd cards made, so a dd image to the end of the card A, > > will not ever install that image on another supposedly identical > > card B or C, they are NOT the same size except in the salespersons > > mind. Therefore, the image must be constrained to a gig or so beyond > > the end of the used portion of the card. And some utility is then > > invoked to look at the card during the initial bootup, that > > re-expands the last partition to encompass the remainder of THAT > > card. > > You could install a bumper partition 8 at the end of the card. > Whatever automat you suffer from, it would have to be extra stupid to > expand partition 7 into the range of the bumper. > > Let's assume a minimum size of rounded up 16 billion with a "16 GB" > medium. Then let's subtract a coward's reserve of 100 million bytes, > and divide by the block size: > ( 15.5e9 - 100e6 ) / 512 = 30078125 > > So if you create partition 8 starting at block 30,078,125 and reaching > up to the end of the usable block range, then the image from block 0 > to the end of partition 7 should be portable to any "16 GB" medium. > > Ideally you should delete partition 8 before copying from the original > medium. So it does not confuse partition editors after the image was > copied to a new medium. > > The GPT header and the backup GPT would have to be re-created with the > new medium size. Partition 8 would have to be re-created from the same > start block up to the end of the usable block range. > gdisk seems to be able to do this. > > Start blocks for bumpers: > Rounded up "8 GB" - 50 MB : 14,550,781 > Rounded up "16 GB" - 100 MB : 30,078,125 > Rounded up "32 GB" - 200 MB : 61,132,812 > Rounded up "64 GB" - 500 MB : 123,046,875 > This is all making sense, gee, I wish you were in charge of the man pages for all this.
I am atm, pulling a new copy out to count=16501000, which is, or should be, a wee bit past the end of partition 7. Then I'll write it to a 32GiB card, and have gparted extend #7 to the end of the disk. I did this earlier today, but all that got me was a kernel panic. But the write to the 32GiB card was likely broken as dd nearly locked up the machine and I finally just ejected the card as I couldn't kill dd even as root. That new copy is made, swap cards wash, rinse & repeat in reverse to a 32G card. > > Have a nice day :) > You too Thomas. And thank you. > Thomas -- Cheers, Gene Heskett -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) Genes Web page <http://geneslinuxbox.net:6309/gene>