All these commands went off without complaint:

apt update
apt-get remove docker docker-engine docker.io containerd runc

apt-get update
apt-get -y install ca-certificates curl gnupg lsb-release
mkdir -p /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/debian/gpg | sudo gpg --d
+earmor -o /etc/apt/keyrings/docker.gpg
echo "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrin
+gs/docker.gpg] https://download.docker.com/linux/debian $(lsb_release
+ -cs) stable" | sudo tee /etc/apt/sources.list.d/docker.list > /dev/n
+ull


apt-get update
apt-get install -y docker-ce docker-ce-cli containerd.io docker-compos
+e-plugin

systemctl start docker
systemctl enable docker
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Output for root:

root@mypi:~# docker info
Client:
...

Server:
 Containers: 0
...
WARNING: No blkio throttle.write_iops_device support
root@mypi:~#
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Looks all good. But then as pi, I failed:

root@mypi:~# exit
logout
$ which docker
/usr/bin/docker
$ docker info
Client:
...

Server:
ERROR: permission denied while trying to connect to the Docker daemon 
+socket at unix:///var/run/docker.sock: Get "http://%2Fvar%2Frun%2Fdoc
+ker.sock/v1.24/info": dial unix /var/run/docker.sock: connect: permis
+sion denied
errors pretty printing info
$ whoami
pi
$
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Then I thought, gosh, root can give pi permissions like this:

usermod -aG docker pi
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, restart and see if I can pull some files:

$ docker info
...

Server:
 Containers: 0
  Running: 0
...
WARNING: No blkio throttle.write_iops_device support
$ whoami
pi
$ docker run -t -i -v $(pwd)/data:/code/data openelevation/open-elevat
+ion /code/create-tiles.sh  /code/data/SRTM_NE_250m.tif 10 10
Unable to find image 'openelevation/open-elevation:latest' locally
latest: Pulling from openelevation/open-elevation
345e3491a907: Pull complete 
...
4f4fb700ef54: Pull complete 
Digest: sha256:82fb21612e86ba847c1f30b6c9a2f457a26a929841a5754282ee2c9
+fea018639
Status: Downloaded newer image for openelevation/open-elevation:latest
WARNING: The requested image's platform (linux/amd64) does not match t
+he detected host platform (linux/arm/v7) and no specific platform was
+ requested
exec /code/create-tiles.sh: exec format error
$
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I didn't understand this ultimate command, and I don't find any evidence of

/code
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on my machine.

Q1) Do I need to be worried about this mismatch?

WARNING: The requested image's platform (linux/amd64) does not match t
+he detected host platform (linux/arm/v7) and no specific platform was
+ requested
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I know I've downloaded 1.2 gigs of data, but I don't know where: (?)

$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/root        29G  9.8G   18G  36% /
...
$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/root        29G   11G   18G  38% /
...
$
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