How to mount rhcos qcow2 root partition

mount_rhcos_qcow2_root_partition_log.txt

$ sudo qemu-nbd --connect /dev/nbd0 rhcos-4.5.2-x86_64-openstack.x86_64.qcow2

$ lsblk /dev/nbd0
NAME     MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
nbd0      43:0    0   16G  0 disk
├─nbd0p1  43:1    0  384M  0 part
├─nbd0p2  43:2    0  127M  0 part
├─nbd0p3  43:3    0    1M  0 part
└─nbd0p4  43:4    0    3G  0 part

$ sudo parted /dev/nbd0 print
Model: Unknown (unknown)
Disk /dev/nbd0: 17.2GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags:

Number  Start   End     Size    File system  Name        Flags
 1      1049kB  404MB   403MB   ext4         boot
 2      404MB   537MB   133MB   fat16        EFI-SYSTEM  boot, esp
 3      537MB   538MB   1049kB               BIOS-BOOT   bios_grub
 4      538MB   3752MB  3214MB               luks_root

$ part_id=$(sudo parted /dev/nbd0 print | awk '/luks_root/ {print $1}')
$ echo ${part_id}
4

$ dev=/dev/nbd0p${part_id}
$ echo $dev
/dev/nbd0p4

[ori@pooh work]$ sudo cryptsetup luksDump ${dev}
LUKS header information
Version:        2
Epoch:          5
Metadata area:  16384 [bytes]
Keyslots area:  16744448 [bytes]
UUID:           00000000-0000-4000-a000-000000000002
Label:          crypt_rootfs
Subsystem:      (no subsystem)
Flags:          (no flags)

Data segments:
  0: crypt
        offset: 16777216 [bytes]
        length: (whole device)
        cipher: cipher_null-ecb
        sector: 512 [bytes]

Keyslots:
  0: luks2
        Key:        256 bits
        Priority:   normal
        Cipher:     cipher_null-ecb
        Cipher key: 256 bits
        PBKDF:      argon2i
        Time cost:  4
        Memory:     524288
        Threads:    1
        Salt:       4a 07 0a 88 f3 d5 fb aa 97 72 b5 c1 be 85 08 f7
                    67 8d c3 99 e9 34 95 bc a5 dc cb 36 5a 44 7c 3a
        AF stripes: 4000
        AF hash:    sha256
        Area offset:32768 [bytes]
        Area length:131072 [bytes]
        Digest ID:  0
Tokens:
  9: coreos
        Keyslot:  0
Digests:
  0: pbkdf2
        Hash:       sha256
        Iterations: 238312
        Salt:       60 b5 67 87 39 cc 53 e7 f8 ea 83 50 ac 0f 9d b5
                    04 9c dd be 4b 6f 03 89 ab 95 cc 3a 48 3d 64 0c
        Digest:     1a 4d 8b 3c 19 26 10 d8 0f 1b d4 68 5b 10 ea 71
                    23 0d f4 c9 d0 bb a0 f3 34 95 ba f7 73 7b de 7a

$ cipher=$(sudo cryptsetup luksDump ${dev} | awk '/cipher/{print$NF;exit}')
$ echo "${cipher}"
cipher_null-ecb

$ LUKS_HEADER_OFFSET_SECTORS=32768
$ dev_size=$(($(sudo blockdev --getsize ${dev}) - ${LUKS_HEADER_OFFSET_SECTORS}))
$ echo "${dev_size}"
6244352

$ echo "0 ${dev_size} linear ${dev} ${LUKS_HEADER_OFFSET_SECTORS}" | sudo dmsetup create coreos-luks-root-nocrypt

$ ls -l /dev/mapper/coreos-luks-root-nocrypt
lrwxrwxrwx. 1 root root 7 Aug 20 11:39 /dev/mapper/coreos-luks-root-nocrypt -> ../dm-2

$ sudo mount /dev/mapper/coreos-luks-root-nocrypt /mnt

$ df /mnt
Filesystem                           1K-blocks    Used Available Use% Mounted on
/dev/mapper/coreos-luks-root-nocrypt   3111936 2307512    804424  75% /mnt

$ ls /mnt
boot  ostree