I have a problem resizing a persistent disks. The disk "z-temp" (10GB) has only one partition (with Ubuntu 16).
I follow the google guide here:
<https://cloud.google.com/compute/docs/disks/add-persistent-disk#resize_partitions>
and I have a problem with step 3.
When I run the command

```
sudo resize2fs /dev/disk/by-id/google-z-temp

```

this is the result:

```
resize2fs 1.42.13 (17-May-2015)
resize2fs: Device or resource busy while trying to open /dev/disk/by-id/google-z-temp
Couldn't find valid filesystem superblock.

```

What is the problem?