My question is regarding the 'loop' devices.
What you are looking at with
lsblk is the complicated mount structure of a running linux live system.
loop0 7:0 0 252.5M 1 loop /run/archiso/sfs/airootfs
A loop device is only a virtual device - it's main idea is to turn a single big (compressed) file into a filesystem. It should maybe be called "deloop" device.
Above line shows how linux from and on the USB drive has mounted a loop device on point
/run, which in turn is a virtual device based on RAM.
findmnt is the utility to get an overview.
The terminology is often unclear. Best consult wikipedia for the concepts. Quick washup:
ssd, hdd: products, not linux "devices". mass storage internal and external. Check dmesg at boot to see how the kernel approaches them. One speaks of "external HDD", or "USB SSD" (meaning external also!): giving info and avoiding the ambiguous term "device".
sda, sdb: recognized and alphabetically numbered disks. Anything more complex than floppy disk needs partitioning:
sda1, sda2: partititions, or block devices to be formatted with a filesystem. Only then your SSD can begin to store files (not just bytes)
Just for illustration: with RAID e.g. you add an extra "volume" level, for added functionality.
And the "famous"
dd utility can write to both: disks and partitions. Both are "block devicey" enough.
Careful when you use it! you "only" need it to make a bootable USB drive (or disk)(or stick or pen drive...), and then you have to get that numbering letter "a", "b", "c", ... correct:
dd ... of=/dev/sda # This can "wipe" a whole internal disk.
dd ... of=/dev/sdb # oops. THIS is the external USB drive attached
dd ... of=/dev/sda1 # first partition on first disk e.g. rootfs
dd ... of=/dev/sda7 # number seven, could be swap partition
fdisk -l gives a good list of partitions with their sizes and types per disk. Dont start fdisk interactively just to get that info.
Yes, without that background you will have a hard time installing linux. As I say: the words "ssd" and "device" are often used imprecisely. Now you know better!
The basic concept behind all this is concentrated in the
mount command. That is what you want to be able to do, at startup, as sysadmin and as user:
mkdir data-f # create mountpoint (first time only)
mount /dev/sdf35 data-f
The contents of that sata disk "sdf", partition #35, are now accessible as files:
cd data-f; ls; ...