I decided to take on a journey of containerization and learn more how containers work under the hood to gain more confidence and become a more proficient programmer. I am trying to run a simple nginx container in runc but I am stuck. I looked at the official documentation but there is not much details, I also googled it but didn't find any details so feel I need more guidance.
I have created an OCI bundle and acquired the root file system off of nginx image.
mkdir containers/nginx/rootfs
cd containers/nginx
docker export $(docker create nginx:alpine) | tar -C rootfs -xvf -
runc spec
Running sudo runc run mynginx gives me the default sh process but when I run nginx inside the container it errors out
/ # nginx
2023/03/12 22:33:52 [emerg] 6#6: chown("/var/cache/nginx/client_temp", 101) failed (1: Operation not permitted)
nginx: [emerg] chown("/var/cache/nginx/client_temp", 101) failed (1: Operation not permitted)
Why? Am I not root?
/ # id
uid=0(root) gid=0(root)
I am.
The listing, though, shows that only /dev/, /proc and /sys are owned by root, other folders are owned by user 1001.
/ # ls -l
total 64
drwxr-xr-x 2 1001 1001 4096 Feb 10 16:45 bin
drwxr-xr-x 5 root root 360 Mar 12 22:33 dev
drwxr-xr-x 2 1001 1001 4096 Feb 11 10:04 docker-entrypoint.d
-rwxrwxr-x 1 1001 1001 1616 Feb 11 10:03 docker-entrypoint.sh
drwxr-xr-x 21 1001 1001 4096 Mar 12 20:35 etc
-rw-r--r-- 1 1001 1001 0 Mar 12 21:59 hello
drwxr-xr-x 2 1001 1001 4096 Feb 10 16:45 home
drwxr-xr-x 7 1001 1001 4096 Feb 11 10:04 lib
drwxr-xr-x 5 1001 1001 4096 Feb 10 16:45 media
drwxr-xr-x 2 1001 1001 4096 Feb 10 16:45 mnt
drwxr-xr-x 2 1001 1001 4096 Feb 10 16:45 opt
dr-xr-xr-x 306 root root 0 Mar 12 22:33 proc
drwx------ 2 1001 1001 4096 Mar 12 21:26 root
drwxr-xr-x 2 1001 1001 4096 Feb 10 16:45 run
drwxr-xr-x 2 1001 1001 4096 Feb 10 16:45 sbin
drwxr-xr-x 2 1001 1001 4096 Feb 10 16:45 srv
dr-xr-xr-x 13 root root 0 Mar 12 22:33 sys
drwxrwxr-x 2 1001 1001 4096 Feb 11 10:04 tmp
drwxr-xr-x 7 1001 1001 4096 Feb 10 16:45 usr
drwxr-xr-x 12 1001 1001 4096 Feb 10 16:45 var
What is going on? Can you help me?