CentOS Stream 8
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Podman : Use by common users
2021/03/22
 
It's possible to use Podman containers by common users.
[1] By default, sub UID/GID that are used on user name spaces are asigned to run containers.
# default name spaces number

[root@dlp ~]#
cat /proc/sys/user/max_user_namespaces

63175
# sub UID/GID mapping file

# 100000 to 165535 (100000 + 65536 - 1) UID are used for running processes in containers on [cent] user

[root@dlp ~]#
cat /etc/subuid

cent:100000:65536
[root@dlp ~]#
cat /etc/subgid

cent:100000:65536
# when added new users, sub UID/GID are also added

# n=0, n++

# [start UID/GID = 100000 + (65536 * n)]

# [end UID/GID = (start UID/GID) + 65536 - 1]

[root@dlp ~]#
useradd centos

[root@dlp ~]#
useradd redhat

[root@dlp ~]#
cat /etc/subgid /etc/subgid

cent:100000:65536
centos:165536:65536
redhat:231072:65536
cent:100000:65536
centos:165536:65536
redhat:231072:65536
[2] It's possible to run [podman] by common users.
[centos@dlp ~]$
podman pull centos

[centos@dlp ~]$
podman images

REPOSITORY                  TAG     IMAGE ID      CREATED       SIZE
registry.centos.org/centos  latest  2f3766df23b6  3 months ago  217 MB

[centos@dlp ~]$
podman run centos echo "run rootless containers"

run rootless containers
# containers related files are located under the [$HOME/.local] directory

[centos@dlp ~]$
ll ~/.local/share/containers/storage

total 4
drwx------. 2 centos centos  39 Mar 19 11:38 cache
drwx------. 2 centos centos  27 Mar 19 11:38 libpod
drwx------. 2 centos centos   6 Mar 19 11:38 mounts
drwx------. 5 centos centos 159 Mar 19 11:40 overlay
drwx------. 3 centos centos 124 Mar 19 11:40 overlay-containers
drwx------. 3 centos centos 116 Mar 19 11:39 overlay-images
drwx------. 2 centos centos 129 Mar 19 11:40 overlay-layers
-rw-r--r--. 1 centos centos  64 Mar 19 11:40 storage.lock
drwx------. 2 centos centos   6 Mar 19 11:38 tmp
-rw-r--r--. 1 centos centos   0 Mar 19 11:38 userns.lock

# possible to create Pods

[centos@dlp ~]$
podman pod create -p 8081:80 -n test-pod

[centos@dlp ~]$
podman pod ls

POD ID        NAME      STATUS   CREATED        INFRA ID      # OF CONTAINERS
9e99670113a1  test-pod  Created  7 seconds ago  96a40c2b7c37  1

# for port mapping,

# it's impossible to use less than [1024] ports on Host machine by common users

# possible to use over [1024] ports

[centos@dlp ~]$
podman run -d -p 1023:80 srv.world/centos-nginx

Error: rootlessport cannot expose privileged port 1023, you can add 'net.ipv4.ip_unprivileged_port_start=1023' to /etc/sysctl.conf (currently 1024), or choose a larger port number (>= 1024): listen tcp 0.0.0.0:1023: bind: permission denied
[centos@dlp ~]$
podman run -d -p 1024:80 srv.world/centos-nginx

[centos@dlp ~]$
podman ps

CONTAINER ID  IMAGE                   COMMAND               CREATED             STATUS                 PORTS                 NAMES
377f620d7bf8  srv.world/centos-nginx  /usr/sbin/nginx -...  About a minute ago  Up About a minute ago  0.0.0.0:1024->80/tcp  vigilant_proskuriakova
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