ubuntu 下的文件系统initramfs解压缩_lsinitramfs_Robert_Y_Zhang的博客-CSDN博客
https://blog.csdn.net/weixin_40191420/article/details/107486888
系统： ubuntu 16.04
解压镜像：
/boot/initrd.img-4.15.0-107-generic需要额外安装的工具：
sudo apt-get install binwalk -y
- 使用lsinitramfs工具查看initramfs的具体文件
lsinitramfs /boot/initrd.img-4.15.0-107-generic
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- 使用binwalk查看initramfs内包含的格式
binwalk /boot/initrd.img-4.15.0-107-generic DECIMAL HEXADECIMAL DESCRIPTION -------------------------------------------------------------------------------- 0 0x0 ASCII cpio archive (SVR4 with no CRC), file name: ".", file name length: "0x00000002", file size: "0x00000000" 112 0x70 ASCII cpio archive (SVR4 with no CRC), file name: "kernel", file name length: "0x00000007", file size: "0x00000000" 232 0xE8 ASCII cpio archive (SVR4 with no CRC), file name: "kernel/x86", file name length: "0x0000000B", file size: "0x00000000" 356 0x164 ASCII cpio archive (SVR4 with no CRC), file name: "kernel/x86/microcode", file name length: "0x00000015", file size: "0x00000000" 488 0x1E8 ASCII cpio archive (SVR4 with no CRC), file name: "kernel/x86/microcode/AuthenticAMD.bin", file name length: "0x00000026", file size: "0x00006B2A" 28072 0x6DA8 ASCII cpio archive (SVR4 with no CRC), file name: "TRAILER!!!", file name length: "0x0000000B", file size: "0x00000000" 28672 0x7000 ASCII cpio archive (SVR4 with no CRC), file name: "kernel", file name length: "0x00000007", file size: "0x00000000" 28792 0x7078 ASCII cpio archive (SVR4 with no CRC), file name: "kernel/x86", file name length: "0x0000000B", file size: "0x00000000" 28916 0x70F4 ASCII cpio archive (SVR4 with no CRC), file name: "kernel/x86/microcode", file name length: "0x00000015", file size: "0x00000000" 29048 0x7178 ASCII cpio archive (SVR4 with no CRC), file name: "kernel/x86/microcode/GenuineIntel.bin", file name length: "0x0000002A", file size: "0x002DD400" 3032592 0x2E4610 ASCII cpio archive (SVR4 with no CRC), file name: "TRAILER!!!", file name length: "0x0000000B", file size: "0x00000000" 3033088 0x2E4800 gzip compressed data, from Unix, last modified: 2020-07-06 05:10:31 46149573 0x2C02FC5 Cisco IOS microcode, for "" 56593448 0x35F8C28 MySQL ISAM compressed data file Version 11
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从上面可以看出，再3033088处开始，是gzip压缩格式的数据，从这是initramfs中的文件系统。
3. 解压dd if=/boot/initrd.img-4.15.0-107-generic bs=3033088 skip=1 | zcat | cpio -id --no-absolute-filenames -v
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bin conf etc init lib lib64 run sbin scripts usr var
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initrd使用lzma压缩的。那么解压时候就不能用zcat命令了。应该使用如下命令：
dd if=/mnt/casper/initrd bs=1540096 skip=1 | lzcat | cpio -id --no-absolute-filenames -v lzcat=xz --format=lzma --decompress --stdout
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- 压缩
find . | cpio --quiet --dereference -o -H newc | gzip -9 > ~/new-initrd.gz
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或
find . | cpio --quiet --dereference -o -H newc | lzma -7 > ~/new-initrd.lz
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参考：
https://blog.csdn.net/xiaofeng_yan/article/details/83303544
https://www.computerhope.com/unix/xz.htm
https://askubuntu.com/questions/777260/how-to-repack-initrd-img
https://wiki.ubuntu.com/CustomizeLiveInitrd
