Reset root password of a virtual machine

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Hierarchy: VMmanager KVM -> VIRTUAL MACHINES
VMmanager Cloud -> VIRTUAL MACHINES

To change the root password of a virtual machine, the corresponding method must be specified in the OS template.

Password change method is an algorithm used by VMmanager for changing the root password of a virtual machine. The method is specified on the OS template in the tag chpass_method

Only the mount.linux method is currently supported

mount.linux

This method can be used only on Linux systems. guestfish must be installed

How it works


1. VMmanager mounts the virtual disk:

guestmount -a <disk_image> -i <path to the mounting point>

2. Makes chroot

mount -t proc proc <path to the mounting point>/proc
mount -o bind /dev <path to the mounting point>/dev mount -o bind /sys <path to the mounting point>/sys chroot <path to the mounting point>

3. Changes the password

usermod -p 'new password' root

4. Make unmount

"Failed to mount VM disks" after password change

This error occurs when trying to change the password of a virtual machine running the XFS file system located on a ext4 host server, kernel version 3.10 and later.

Run guestmount -v -x -a <disk_image> -i <path to mount point>. If you see something like this "mount: wrong fs type, bad option, bad superblock", that virtual machine cannot run with libguestfs.

Cause of the issue: guest xfs is not fully supported by the RHEL/CentOS 6 kernel. For more information, please refer to virt-inspector can't obtain info from rhel7.3 guest image on rhel6.9 host.

Unfortunately, libguestfs developers say that this bug cannot be resolved.