The command virsh pool-create-as vms dir --target /vms creates and starts a transient storage pool named vms of type dir with the target directory /vms12. This command resolves the issue of the storage pool not found error, as it makes the existing directory /vms visible to libvirt as a storage pool. The other commands are invalid because:
* dd if=/dev/zero of=/vms bs=1 count=0 flags=name:vms is not a valid command syntax. The dd command does not take a flags argument, and the output file /vms should be a regular file, not a directory3.
* libvirt-poolctl new --name=/vms --type=dir --path=/vms is not a valid command name. There is no such command as libvirt-poolctl in the libvirt package4.
* qemu-img pool vms:/vms is not a valid command syntax. The qemu-img command does not have a pool subcommand, and the vms:/vms argument is not a valid image specification5.
* touch /vms/.libvirtpool is not a valid command to create a storage pool. The touch command only creates an empty file, and the .libvirtpool file is not recognized by libvirt as a storage pool configuration file6.
References:
* 1: virsh - difference between pool-define-as and pool-create-as - Stack Overflow
* 2: dd(1) - Linux manual page - man7.org
* 3: 12.3.3. Creating a Directory-based Storage Pool with virsh - Red Hat Customer Portal
* 4: libvirt - Linux Man Pages (3)
* 5: qemu-img(1) - Linux manual page - man7.org
* 6: touch(1) - Linux manual page - man7.org