Okay, so of interest but maybe not applicable to my usecase. Thanks:)
Yeah, it remains to be seen how complex the actual format/code is. Would need to balance the difficulty of recreating it (which I assume to be quite high) against difficulty of extracting kernel code... although https://github.com/lkl/linux exists so for all I know maybe it's easy¯\_(ツ)_/¯
And yes, if I needed to actually write a "tar2ext4" tool today - like, start working in the morning and have it done by EOD - I would absolutely use... actually probably a loopback device rather than a true ramdisk, but yeah. But that requires root access and fiddling with loopback config, which seems excessive for what is, ultimately, just another archive format (from a certain point of view). And honestly some of it is just that it sounds fun to get my hands dirty with filesystem code in userspace:)
(Forgive my replying to myself; I'm out of the edit window and this seemed good to leave in case someone stumbles across this comment)
Yeah so I'm maybe a touch dumb and missed this right in the lkl readme - their demos all but include that exact function:
fs2tar - a tool that converts a filesystem image to a tar archive
cptofs/cpfromfs - a tool that copies files to/from a filesystem image
lklfuse - a tool that can mount a filesystem image in userspace, without root priviledges, using FUSE
Yeah, it remains to be seen how complex the actual format/code is. Would need to balance the difficulty of recreating it (which I assume to be quite high) against difficulty of extracting kernel code... although https://github.com/lkl/linux exists so for all I know maybe it's easy¯\_(ツ)_/¯
And yes, if I needed to actually write a "tar2ext4" tool today - like, start working in the morning and have it done by EOD - I would absolutely use... actually probably a loopback device rather than a true ramdisk, but yeah. But that requires root access and fiddling with loopback config, which seems excessive for what is, ultimately, just another archive format (from a certain point of view). And honestly some of it is just that it sounds fun to get my hands dirty with filesystem code in userspace:)