Docker Dockerfile sudo
▌Problem
We have a Dockerfile
that will switch user to run a shell script on ENTRYPOINT, however we got the 2
problems,
1. Cannot get the environment variables in the shell script.
2. Get permission denied after we preserve the environment
variables when sudo user.
Here are the
sample files,
▋Dockerfile
▋Shell script
(callback.sh)
The
container from the above Dockerfile could not get the environment variables $POSTGRES_USER
and $POSTGRES_PASSWORD,
and finally output,
|
POSTGRES_USER= POSTGRES_PASSWORD= |
And the log file
will be located at /var/lib/postgresql/my_log.
▌Environment
▋Docker desktop 2.3.0.3
▌Solution
▋Preserving environment variables
The problem was due
to not preserving environment variables when switching to other user.
So we have to
preserve the existing environment variables by adding the argument -U
when sudo. (See sudo
manual)
|
-E, --preserve-env: Indicates to the security policy that
the user wishes to preserve their existing environment variables. The
security policy may return an error if the user does not have permission to
preserve the environment. |
So we must update the following line of Dockerfile,
But it caused the second problem:
Permission denied when writing log to ~/my_log.
The output became as following,
|
POSTGRES_USER=postgres POSTGRES_PASSWORD=xxxxx callback.sh: 3: callback.sh: cannot create /root/my_log: Permission denied |
As you can see the ~/
is changed to /root/ but not /var/lib/postgresql/, so
that the user: postgres could not have the permission on ~/.
Finally I solved the problems by updating
the Dockerfile as following,
▋Dockerfile
# Or use this # ENTRYPOINT ["/bin/sh", "-c", "su --preserve-environment - postgres callback.sh'"]
▋Shell script
(callback.sh)
#!/bin/bash echo POSTGRES_USER=$POSTGRES_USER echo POSTGRES_PASSWORD=$POSTGRES_PASSWORD echo "some logs" >> /var/lib/postgresql/my_log
