AFAIK the command in OS-X is plain 'md5 filename', not 'md5sum filename'
Thanks for the tip; that worked, the .iso checked out good.
So I proceed.
Next I ran into a couple mysterious glitches using UNetbootin to create the Bootable USB using the Bodhi Linux branded flash drive (following the Installation Instructions Wiki page):
During the installation process, an alert appeared: "The file /Volumes/BODHI LINUX/isolinux/isohdpfx.bin already exists." I hadn't looked at the Bodhi Linux USB drive to see if there was anything on it – but later when I repeated the procedure after I'd erased the USB drive UNetbootin showed the same alert, though I knew the drive was empty. Anyway, I went ahead and told it to replace All.
When the installation on the USB drive was complete, UNetbootin reported: "The created USB device will not boot off a Mac. Insert it into a PC, and select the USB boot option in the BIOS boot menu." Indeed, the USB drive didn't show in the Startup Disk Preference Pane (nor would I expect it to, since it is not a MacOS volume). However, when I restarted the MacBook Pro in the Startup Manager (with the option key pressed, shows all possible startup volumes), two extra volumes appeared, identified as "Windows" and "EFI Boot". Selected "Windows", but got a black screen with a message saying "Boot error". Selected "EFI Boot", and it worked fine, except that most of the type on the screen was extremely tiny – possibly due to the very fine native resolution of the display (2013 model, retina 15", 220ppi)? (I presume this can be dealt with once Bodhi Linux is installed?) When I tried the MacBook (not Pro), the Bootable USB showed only as "EFI Boot", and started the computer fine, with easily readable type (13" screen, 1200x800).
Meanwhile, I had a lot of trouble with the Bodhi Linux USB drive, which I couldn't get to make a reliable connection in either of the MacBook Pro's USB ports. Turns out its USB connector plug, which extends out of the housing when the handle is pushed, is about a millimeter shorter than any other USB plug I have, so when inserted it barely makes a connection, and disconnects (unmounts) easily (as in right in the middle of an operation) if touched or bumped. Is this particular one faulty, or are they all like this?
(I also tried another utility named Etcher to make a Bootable USB, having heard about it from this article by another Mac user who said he couldn't get UNetbootin to work. Etcher worked, but with some even more weird glitches, so I went back to UNetbootin.)
So I continued with the MacBook (2008 Aluminum Unibody model), which is where I want to install Bodhi anyway. The HD in the MacBook has several partitions, each with a different version of MacOS installed. I erased one partition I didn't need, formatting it in FAT32. (MacOS Disk Utility also offers ExFAT format, and explains: "MS-DOS (FAT): Use for Windows volumes that are 32 GB or less. ExFAT: Use for Windows volumes that are over 32 GB." Should I then use ExFAT instead for a 50 GB volume?)
Once the MacBook was running from the Bootable USB, I clicked the little leaf at the lower left, to Install Bodhi Linux. Selected English. Did not check "Download updates" and "Install third-party software"; get to those later.
Next is "Installation type". Not sure what "Install Bodhi alongside them" does; when I selected it, the next screen showed two panels, under the legend "Allocate drive space by dragging the divider below:"
On the left with an icon of a file folder it said:
Files (8.7 GB)
While on the right was an Ubuntu icon (?) and:
Then below: "8 smaller partitions are hidden. use [sic] the advanced partitioning tool for more control" I clicked on that, and it took me to the same screen that shows when "Something else" is selected in the Installation type screen, displaying a list of the present partitions. The partition I intended to use is at /sda4, 50 GB, formatted as FAT32; apparently the "Files" panel above refers to that, though it says it's now only 27.9 GB. /sda5 is presently another 50 GB partition with MacOS installed; I certainly don't want to delete/erase/replace it.
Anyway, in this "Installation type" window with the list of partitions presently on the disk, at the bottom under "Device for boot loader installation" I saw a dropdown menu with a duplicate of the list of partitions, so I selected /dev/sda4, the 50 GB FAT32 volume I'd created. Then selected "Install Now", and an alert appeared:
"No root file system. No root file system is defined. Please correct this from the partitioning menu." I don't see a "partitioning menu", but there is a button that says "New Partition Table…"; however it is inactive. It becomes active if I select "/dev/sda" at the top of the partition list, which I understand to be selecting the entire disk. And indeed, I am warned that continuing with "New Partition Table…" will repartition and erase the entire disk (losing several hundred GB of data), which I certainly don't want to do.
The Installation Instructions Wiki page simply assumes that "Erase disk and install Bodhi" is the user's choice, says nothing about the "Something else" option. The instructions appear not to have been updated since Bodhi 3.0.0; anyway I didn't see the first screen pictured at all.
I also came across a PDF titled "Step-by-Step Guide to Bodhi Linux 4" by Roger Carter (I don't remember where I got it, thought it was on the Bodhi Linux site, but don't find it there now), but it makes the same assumption.
I did an Internet search for "bodhi linux installation" and found a couple other sets of instructions, but again, both assumed I was ready to erase the computer's disk to install BL. Which I'm not. I just want to put it on the empty partition I prepared for it.