Failure, exiting. Can't find log. about docker-postgres-upgrade HOT 2 CLOSED

also u can do something like

# find out the hash of  the last run docker
docker ps -a | head
docker commit THE_HASH test1
docker run -it --rm --entrypoint=sh test1

# in the container
ls -l
cat pg_upgrade_dump_116017.log

from docker-postgres-upgrade.

you can mount a folder in your host to /var/lib/postgresql and then you'll see the log.
Example:
docker run --rm
-e POSTGRES_INITDB_ARGS="--wal-segsize=1024"
-v /home/user/db/12/main:/var/lib/postgresql/12/data
-v /home/user/db/13/main:/var/lib/postgresql/13/data
-v /home/user/:/var/lib/postgresql
tianon/postgres-upgrade:12-to-13

from docker-postgres-upgrade.