Permission denied inside Docker container on shared directory - docker

Question

I'm new to Docker so I might not have some of the terminology correct. Inside the container I'm getting a permission denied error on a directory shared with the host. They appear to have matching uid:gid and the permissions host side are 777. The container is not for running in the background.
I'm using the container to run a big series of untrusted programs one at a time each needing the same initial conditions. So I don't think it's feasible to copy stuff into the docker image at build time. I felt the optimal thing to do is copy the programs one at a time to a temp directory on the host and then share that directory with the fresh container for each run. I also need to collect the output from the container-run programs and keep them on the host so I can see how each program's output differs from the others.
I have looked at the following questions/answers:
Docker: Copying files from Docker container to host
How to fix docker: Got permission denied issue - successfully used to make docker run as someone other than root
How do I add a user when I'm using Alpine as a base image? and Setting up a new user - used to create the user and group
I am:
running docker as an ordinary user uid 1000, gid 1000, also belonging to the group docker
setting permissions on the shared directory host side to be 777 with uid:gid as 1000:1000 which is the same as the user
setting the uid and gid inside the container to match uid and gid from the host
using the Dockerfile to create a uid and gid each of 1000
I read here that If the first argument begins with a / or ~/, you’re creating a bindmount. Remove that, and you’re naming the volume. So I tried both. The bindmount version seems to have the correct uid:gid but is permission denied, the volume version comes out as root:root.
As a newbie it's hard to know what information to share so here's everything I think might be useful:
Docker command attempt 1
[osboxes#osboxes tmp]$ pwd
/var/tmp
osboxes#osboxes tmp]$ whoami
osboxes
[osboxes#osboxes tmp]$ grep osboxes /etc/passwd
osboxes:x:1000:1000:osboxes.org:/home/osboxes:/bin/bash
[osboxes#osboxes tmp]$ groups
osboxes wheel vboxsf docker
[osboxes#osboxes tmp]$ grep osboxes /etc/group
wheel:x:10:osboxes
osboxes:x:1000:osboxes
vboxsf:x:981:osboxes
docker:x:1001:osboxes
[osboxes#osboxes tmp]$ ls -al
total 2
drwxrwxrwt. 11 root root 4096 Dec 31 12:13 .
drwxr-xr-x. 21 root root 4096 Jul 5 05:00 ..
drwxr-xr-x. 2 abrt abrt 6 Jul 5 05:00 abrt
drwxrwxrwx. 2 osboxes osboxes 6 Dec 31 12:13 host
continues...
[osboxes#osboxes tmp]$ docker run --rm -v /var/tmp/host:/var/tmp/container:rw \
--user appuser:appgroup --workdir /var/tmp/container \
-it alpine_bash_jdk11 /bin/bash
bash-5.0$ pwd
/var/tmp/container
bash-5.0$ ls -al
ls: can't open '.': Permission denied
total 0
bash-5.0$ ls -al ..
total 0
drwxrwxrwt 1 root root 23 Dec 31 12:51 .
drwxr-xr-x 1 root root 17 Dec 16 10:31 ..
drwxrwxrwx 2 appuser appgroup 6 Dec 31 12:13 container
bash-5.0$ whoami
appuser
bash-5.0$ groups
appgroup
bash-5.0$ grep appuser /etc/passwd
appuser:x:1000:1000:Linux User,,,:/home/appuser:/sbin/nologin
bash-5.0$ grep appuser /etc/group
appgroup:x:1000:appuser
Docker command attempt 2
everything as before except
for removing the qualified path to the host's
/var/tmp/host directory
docker run --rm -v host:/var/tmp/container:rw \
--user appuser:appgroup --workdir /var/tmp/container \
-it alpine_bash_jdk11 /bin/bash
bash-5.0$ pwd
/var/tmp/container
bash-5.0$ ls -al
total 0
drwxr-xr-x 2 root root 6 Dec 31 12:13 .
drwxrwxrwt 1 root root 23 Dec 31 13:03 ..
bash-5.0$ ls -al ..
total 0
drwxrwxrwt 1 root root 23 Dec 31 13:03 .
drwxr-xr-x 1 root root 17 Dec 16 10:31 ..
drwxr-xr-x 2 root root 6 Dec 31 12:13 container
bash-5.0$ whoami
appuser
bash-5.0$ groups
appgroup
bash-5.0$ echo hello from contanier > container.msg.txt
bash: container.msg.txt: Permission denied
Docker build command
as user osboxes
docker build -t alpine_bash_jdk11 .
Dockerfile
FROM alpine:latest
RUN apk --no-cache update
RUN apk add --no-cache bash
RUN apk --no-cache add openjdk11 --repository=http://dl-cdn.alpinelinux.org/alpine/edge/community
ENV JAVA_HOME="/usr/lib/jvm/default-jvm"
ENV PATH=$PATH:${JAVA_HOME}/bin
RUN addgroup -g 1000 -S appgroup && adduser -S appuser -G appgroup -u 1000
USER appuser
I haven't used docker compose because I'm still getting my head round basic docker.
Virtual Machine which is the Docker Host
CentOS 7.2003 from osboxes.org, organization's decision, not mine
Linux osboxes 3.10.0-1160.11.1.el7.x86_64 #1 SMP Fri Dec 18 16:34:56 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
I did a yum update, then yum installed all the stuff needed to install VirtualBox guest additions which is working ok
Docker version 1.13.1, build 0be3e21/1.13.1
Physical Host
Windows 10 64-bit
VirtualBox 6.1.4r136177
both these are the organization's decisions

Answer 1

tl;dr: had old version of docker due to wrong install command
The answer: install docker-ce instead of docker. Depending on your system that might be
sudo apt-get install -y docker-ce
or
sudo yum -y install docker-ce
instead of sudo apt-get install -y docker
or
sudo yum -y install docker
Solution: update docker
Having found this article I could see that I had the wrong version of docker. I justifiably thought the correct command was
sudo yum install -y docker
but it should have been docker-ce
I had to yum erase -y docker docker-common
Now I have Docker version 20.10.1, build 831ebea