> An archive of files and directories is in itself not a program.
Okay, but you can make the same argument to say that ELF files aren't programs in and of themselves either. In fact, some ELF files are dynamic libraries without an entrypoint, and therefore not actually executable in any meaningful way unless connected to yet another program.
If you can accept that some ELF files are executables and some aren't, then you can also accept that some CPIOs are executables and some aren't. What's the difference between ld.so unpacking an ELF file into RAM and running its entrypoint, and the Linux kernel unpacking an initramfs into RAM and running its entrypoint?
... I think you're reading a bit much into it. It's less that I couldn't afford to pay that, and more that I didn't want to pay that, and iterating on the solution I used to dodge that led me down a giant rabbit hole of learning more about Linux while solving stupider and stupider problems posed for myself.
I did learn about systemctl switch-root after finishing my kexec solution, but I think if you're at the point of reimaging a server over the network, you probably don't care enough to shut it down correctly :)
To be honest, even this has plenty of room to go down. I get the feeling I could have squeezed a couple more MB off if I had actually cut things off of the default Nixpkgs busybox, and possibly also cut a couple of kernel drivers out.
From what it sounds like, because you have a console and therefore aren't dependent on SSHD not getting overwritten, you can just dd the live running system here?
Okay, but you can make the same argument to say that ELF files aren't programs in and of themselves either. In fact, some ELF files are dynamic libraries without an entrypoint, and therefore not actually executable in any meaningful way unless connected to yet another program.
If you can accept that some ELF files are executables and some aren't, then you can also accept that some CPIOs are executables and some aren't. What's the difference between ld.so unpacking an ELF file into RAM and running its entrypoint, and the Linux kernel unpacking an initramfs into RAM and running its entrypoint?