Sometimes you need to change the password to a user in a qcow2 image, to test locally, or if you are using an infrastructure without cloud-init, regardless of the user the procedure is the same.
Depending on the system the packages name could change a little, I'm using Fedora 27 I have installed
[alvaro@lykan 2post]$ sudo dnf install libguestfs libguestfs-tools openssl
Last metadata expiration check: 1:53:31 ago on Mon 16 Jul 2018 01:51:05 PM CDT.
Package libguestfs-1:1.38.2-1.fc27.x86_64 is already installed, skipping.
Package libguestfs-tools-1:1.38.2-1.fc27.noarch is already installed, skipping.
Package openssl-1:1.1.0h-3.fc27.x86_64 is already installed, skipping.
Dependencies resolved.
Nothing to do.
Complete!
Obviously, I have a QEMU environment to test and run the images, a very important part just to know that your steps are working.
[alvaro@lykan 2post]$ guestfish --rw -a ../../Downloads/CentOS-7-x86_64-GenericCloud-1805.qcow2
Welcome to guestfish, the guest filesystem shell for
editing virtual machine filesystems and disk images.Type: ‘help’ for help on commands
‘man’ to read the manual
‘quit’ to quit the shell><.fs> run
100% ⟦▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒⟧ 00:00
><.fs> list-filesystems
/dev/sda1: xfs
><.fs> mount /dev/sda1 /
><.fs> cp /etc/shadow /etc/shadow-original
><.fs> vi /etc/shadow
Inside the vim editor, you will see the file and now you can change the hash of any user (do not close this until you reached the last step), in any other terminal run:
[alvaro@lykan 2post]$ openssl passwd -1 mysuperpassword
$1$GKdzYMMe$q20PpMv5i/QFbmgwOqtZy1
Copy that generated hash and copy inside the first and second colon punctuation symbol (delete every inside this)
Before
root:!!:17687:0:99999:7:::
bin:*:17632:0:99999:7:::
daemon:*:17632:0:99999:7:::
adm:*:17632:0:99999:7:::
lp:*:17632:0:99999:7:::
sync:*:17632:0:99999:7:::
shutdown:*:17632:0:99999:7:::
halt:*:17632:0:99999:7:::
mail:*:17632:0:99999:7:::
operator:*:17632:0:99999:7:::
games:*:17632:0:99999:7:::
ftp:*:17632:0:99999:7:::
nobody:*:17632:0:99999:7:::
systemd-network:!!:17687::::::
dbus:!!:17687::::::
polkitd:!!:17687::::::
rpc:!!:17687:0:99999:7:::
rpcuser:!!:17687::::::
nfsnobody:!!:17687::::::
sshd:!!:17687::::::
postfix:!!:17687::::::
chrony:!!:17687::::::
After
root:$1$GKdzYMMe$q20PpMv5i/QFbmgwOqtZy1:17687:0:99999:7:::
bin:*:17632:0:99999:7:::
daemon:*:17632:0:99999:7:::
adm:*:17632:0:99999:7:::
lp:*:17632:0:99999:7:::
sync:*:17632:0:99999:7:::
shutdown:*:17632:0:99999:7:::
halt:*:17632:0:99999:7:::
mail:*:17632:0:99999:7:::
operator:*:17632:0:99999:7:::
games:*:17632:0:99999:7:::
ftp:*:17632:0:99999:7:::
nobody:*:17632:0:99999:7:::
systemd-network:!!:17687::::::
dbus:!!:17687::::::
polkitd:!!:17687::::::
rpc:!!:17687:0:99999:7:::
rpcuser:!!:17687::::::
nfsnobody:!!:17687::::::
sshd:!!:17687::::::
postfix:!!:17687::::::
chrony:!!:17687::::::
Close the vim editor, save the changes, and exit guestfish
><.fs> quit
[alvaro@lykan 2post]$
Now you can test the image on any cloud environment or using your local QEMU environment.
