Init Ram Disk filesystem – kind of mini OS in order to mount raid and start „the real /root os“.

hostnamectl; # tested on
   Static hostname: debian9
         Icon name: computer-vm
           Chassis: vm
        Machine ID: 532eabca552b4075a8679094397c8dba
           Boot ID: 15ee0b8e8a1e4d1eb1003c4630644091
    Virtualization: microsoft
  Operating System: Debian GNU/Linux 9 (stretch)
            Kernel: Linux 4.12.0cuztom
      Architecture: x86-64

zcat /boot/initrd.img-$(uname -r) |cpio -tiv|less

# to unpack the files to /test
mkdir /test;
cp /boot/initrd.img-$(uname -r) /test/initrd.img-$(uname -r).gz;
gunzip /test/initrd.img-$(uname -r).gz; # unpack step1
cpio -i /test </test/initrd.img-$(uname -r).gz; # unpack step2

DEBIAN9_initrd.img-4.12.0cuztom.content_file_list.txt

suse12 is compressing the kernel with xz instead of gzip

hostnamectl; # tested on
   Static hostname: suse12.domain
Transient hostname: suse12
         Icon name: computer-vm
           Chassis: vm
        Machine ID: fe6bf561a4d4f20df6176faf58fdd5b5
           Boot ID: 56a3ed39491f42f38c1558befa7be3c7
    Virtualization: microsoft
  Operating System: SUSE Linux Enterprise Server 12 SP2
       CPE OS Name: cpe:/o:suse:sles:12:sp2
            Kernel: Linux 4.4.21-69-default
      Architecture: x86-64

xzcat /boot/initrd-4.4.21-69-default |cpio -tiv|less

SUSE12_initrd-4.4.21-69-default.content_file_list.txt

inspired by: https://stackoverflow.com/questions/6377959/how-do-i-mount-a-ubuntu-initrd-img

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