[DIRE NEED] How To Repack System Folder as a Raw Disk Image Ubuntu

Hello,
I was able to unpack the image simply by using the command

Code:

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unrar x system.img

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Now that I have made my modifications (literally only changing the build.prop to start) I need to repack the system file folder back to an "x-raw-disk-image". Does anybody know how I may do this? Thanks everyone!

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