3. Download ubuntu rootfs
$ mkdir ~/rootfs && cd ~/rootfs
pdf: $ wget http://cdimage.ubuntu.com/ubuntu-base/releases/19.10/release/ubuntu-base-19.10-base-arm64.tar.gz

$ wget https://cdimage.ubuntu.com/ubuntu-base/releases/18.04/release/ubuntu-base-18.04.5-base-arm64.tar.gz
Change it and move on
$ mkdir ubuntu-rootfs
pdf: $ tar -xvf ubuntu-base-19.10-base-arm64.tar.gz -C ubuntu-rootfs
$ tar -xvf ubuntu-base-18.04.5-base-arm64.tar.gz -C ubuntu-rootfs
Change it and move on
$ cd ubuntu-rootfs
$ ls
4. Install qemu-user-static on PC to simulate arm64 environment
$ apt-get install qemu-user-static
$ cp /usr/bin/qemu-aarch64-static usr/bin
$ cp -b /etc/resolv.conf etc/
5. Simulate arm64 environment
$ cd ../ (rootfs$)
$ ./ch-mount.sh -m ubuntu-rootfs

Refusing permission
There's no command
Can you help me with this error when an error occurs?