Is there a way to know which files have changed in a docker container compared to its base image?
The docker container diff command shows the differences between a container and its base system.

In the output, files are reported as (A) if the file or directory was added, (D) if a file or directory was deleted or (C) if a file or directory was changed. File permission changes are reported as (C).

she$ CID=$(sudo docker run --rm -d ubuntu sleep 500)
sh$ sudo docker exec $CID touch newfile
sh$ sudo docker exec $CID useradd bob
sh$ sudo docker exec $CID chmod o-x /usr/bin/cut
sh$ sudo docker diff $CID
C /etc
C /etc/group
A /etc/group-
C /etc/gshadow
A /etc/gshadow-
C /etc/passwd
A /etc/passwd-
C /etc/shadow
A /etc/shadow-
C /etc/subgid
A /etc/subgid-
C /etc/subuid
A /etc/subuid-
A /newfile
C /usr
C /usr/bin
C /usr/bin/cut
C /var
C /var/log
C /var/log/faillog
C /var/log/lastlog
C /var/log/tallylog