OpenStack customize CloudImage with backdoor #1

The topic is divided into 2 parts. This section is meant for Linux.

Query Qcow2/raw Image info

fdisk cosmic-server-cloudimg-amd64.img
blkid cosmic-server-cloudimg-amd64.img

Mount Image

guestmount -a cosmic-server-cloudimg-amd64.img -m xx /mnt/xx

sudo losetup -f -P cosmic-server-cloudimg-amd64.img (Not working fo qcow2 format image cuz it won't parse qcow2 header)

sudo modprobe nbd max_part=8
sudo qemu-nbd -c /dev/nbd0 ubuntu.qcow2
sudo qemu-nbd -d /dev/nbd0

Customize Image

chroot /mnt/xx

virt-customize -a bionic-server-cloudimg-amd64.img --root-password password:yourpassword

ssh-keygen -f /etc/ssh/ssh_host_rsa_key -N '' -t rsa //for ssh into cloud image

sudo guestfish --rw -a $IMG_FILE

Cloud Image partition layout

Shrink qcow2 image and root partition

Some times the cloud image don’t have enough space to be customized when hitting huge package via apt install. We have to shrink/increze its size to fill our package.

qemu-img resize $IMG_FILE 4G

e2fsck -f -y -v -C 0 '/dev/nbd0p1' resize2fs -p '/dev/nbd0p1'

GParted 1.0.0

configuration --enable-libparted-dmraid --enable-online-resize

libparted 3.2


Device:	/dev/nbd0
Model:	Unknown
Serial:	none
Sector size:	512
Total sectors:	8388608
Heads:	255
Sectors/track:	63
Cylinders:	522
Partition table:	gpt
Partition	Type	Start	End	Flags	Partition Name	File System	Label	Mount Point
/dev/nbd0p14	Primary	2048	10239	bios_grub		grub2 core.img		
/dev/nbd0p15	Primary	10240	227327	boot, esp		fat32	UEFI	
/dev/nbd0p1	Primary	227328	4612062			ext4	cloudimg-rootfs	

Grow /dev/nbd0p1 from 2.09 GiB to 3.89 GiB  00:00:01    ( SUCCESS )
calibrate /dev/nbd0p1  00:00:00    ( SUCCESS )
path: /dev/nbd0p1 (partition)
start: 227328
end: 4612062
size: 4384735 (2.09 GiB)
check file system on /dev/nbd0p1 for errors and (if possible) fix them  00:00:01    ( SUCCESS )
e2fsck -f -y -v -C 0 '/dev/nbd0p1'  00:00:01    ( SUCCESS )
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information

88962 inodes used (32.45%, out of 274176)
30 non-contiguous files (0.0%)
53 non-contiguous directories (0.1%)
# of inodes with ind/dind/tind blocks: 0/0/0
Extent depth histogram: 76789/10
543158 blocks used (99.10%, out of 548091)
0 bad blocks
1 large file

64601 regular files
12048 directories
9 character device files
0 block device files
0 fifos
19 links
12295 symbolic links (12146 fast symbolic links)
0 sockets
88972 files
e2fsck 1.45.3 (14-Jul-2019)
grow partition from 2.09 GiB to 3.89 GiB  00:00:00    ( SUCCESS )
old start: 227328
old end: 4612062
old size: 4384735 (2.09 GiB)
new start: 227328
new end: 8386559
new size: 8159232 (3.89 GiB)
grow file system to fill the partition  00:00:00    ( SUCCESS )
resize2fs -p '/dev/nbd0p1'  00:00:00    ( SUCCESS )
Resizing the filesystem on /dev/nbd0p1 to 1019904 (4k) blocks.
The filesystem on /dev/nbd0p1 is now 1019904 (4k) blocks long.

resize2fs 1.45.3 (14-Jul-2019)

My Script


BRANCH="stable" # testing nightly

sudo virt-sysprep -a $IMG_FILE \
--run-command "useradd $USERNAME && usermod -aG sudo $USERNAME"

sudo virt-sysprep -a $IMG_FILE \
--run-command "mkdir -p /home/$USERNAME/.ssh && chown $USERNAME:$USERNAME /home/$USERNAME && chmod 700 /home/$USERNAME/.ssh"

sudo virt-sysprep -a $IMG_FILE \
--ssh-inject chris:file:/home/chris/.ssh/

#sudo modprobe nbd max_part=8
#sudo qemu-nbd -c /dev/nbd0 $IMG_FILE
#sudo mkdir /tmp/cloud-target
#sudo mount /dev/nbd0p1 cloud-target
sudo virt-copy-in -a $IMG_FILE $(pwd)/.oh-my-zsh /root/
sudo virt-copy-in -a $IMG_FILE $(pwd)/.zshrc /root/
sudo virt-copy-in -a $IMG_FILE $(pwd)/.oh-my-zsh /home/$USERNAME
sudo virt-copy-in -a $IMG_FILE $(pwd)/.zshrc /home/$USERNAME

sudo mkdir /tmp/cloud-target
sudo guestmount -a $IMG_FILE -m /dev/sda1 /tmp/cloud-target

sudo chroot /tmp/cloud-target /bin/bash <<EOF
sed -i 's/' /etc/apt/sources.list
sed -i 's/' /etc/apt/sources.list
sed -i 's/ubuntu/root/g' /root/.zshrc
sed -i 's/ubuntu/${USERNAME}/g' /home/${USERNAME}/.zshrc
chown -R root:root /root/
chown -R ${USERNAME}:${USERNAME} /home/${USERNAME}/

# sudo umount /dev/nbd0p1
sudo umount /tmp/cloud-target

sudo virt-customize -a $IMG_FILE --root-password password:yourpassword

sudo virt-customize -v -x -a $IMG_FILE \
    --timezone "Asia/Hong_Kong" 

sudo virt-customize -v -x -a $IMG_FILE \
    --update \
    --install vim,bash-completion,wget,curl,telnet,unzip
sudo virt-customize -v -x -a $IMG_FILE \
    --update \
    --install zsh,openjdk-8-jdk,maven

sudo virt-customize -v -x -a $IMG_FILE --upload $CLOUD_CONFIG:/etc/cloud/cloud.cfg
sudo virt-customize -v -x -a $IMG_FILE --upload $DOCKER_DEPLOYSCRIPT:/home/$USERNAME/

sudo virt-customize -v -x -a $IMG_FILE \
    --run-command "/home/$USERNAME/"

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