How do I unpack initrd of ubuntu 18.04 and then pack it back?

I used binwalk to unpack initrd of ubuntu 18.04 But it didnt unpack the package command used # sudo binwalk initrd =========== result: ========== DECIMAL HEX DESCRIPTION ——————————————————————————————————- 0 0x0 ASCII cpio archive (SVR4 with no CRC), file name: “.” 112 0x70 ASCII cpio archive (SVR4 with no CRC), file name: “kernel” 232 0xE8 ASCII…

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