Ubuntu – Add user in the docker to specific group, but not working

I create the user "ros" inside the docker and add it in group "sudo", as shown in the docker script below.

FROM ubuntu:20.04
[...]
RUN useradd --create-home --shell /bin/bash -G sudo ros
[...]

However, the group adding never success. I also tried "usermod -aG sudo ros" and the result is the same.

Here is the brief description of the environment I am using:
Host machine: ubuntu 20.04 on x64
Docker image: based on ubuntu 20.04

After restarting docker container, I checked with the command ‘id’ and it seems that the user is not added into "sudo" group. I also checked /etc/group but it shows the user "ros" is in group "sudo".

Currently I am using "exec newgrp sudo" for my work. However, I also want to add the user to group "dialout" and the same problem remains, so I need to know how I can add user to a certain group in Docker.

Does anyone know what step I might miss? Please notify me if I should provide any other information.

Edit:
Here are the /etc/group file and docker inspect output:
/etc/group file

root:x:0:
daemon:x:1:
bin:x:2:
sys:x:3:
adm:x:4:
tty:x:5:
disk:x:6:
lp:x:7:
mail:x:8:
news:x:9:
uucp:x:10:
man:x:12:
proxy:x:13:
kmem:x:15:
dialout:x:20:ros
fax:x:21:
voice:x:22:
cdrom:x:24:
floppy:x:25:
tape:x:26:
sudo:x:27:ros
audio:x:29:pulse
dip:x:30:
www-data:x:33:
backup:x:34:
operator:x:37:
list:x:38:
irc:x:39:
src:x:40:
gnats:x:41:
shadow:x:42:
utmp:x:43:
video:x:44:
sasl:x:45:
plugdev:x:46:
staff:x:50:
games:x:60:
users:x:100:
nogroup:x:65534:
systemd-timesync:x:101:
systemd-journal:x:102:
systemd-network:x:103:
systemd-resolve:x:104:
messagebus:x:105:
input:x:106:
kvm:x:107:
render:x:108:
bluetooth:x:109:
rdma:x:110:
rtkit:x:111:
ssh:x:112:
netdev:x:113:
lpadmin:x:114:
avahi:x:115:
scanner:x:116:saned
saned:x:117:
colord:x:118:
geoclue:x:119:
pulse:x:120:
pulse-access:x:121:
gdm:x:122:
ros:x:1000:

And docker inspect:

[
    {
        "Id": "d5d54dc25c439cd417bd661a3c97c62001f69abc1946a461c2c93911c493db28",
        "Created": "2023-06-01T18:42:44.891896943Z",
        "Path": "/bin/bash",
        "Args": [],
        "State": {
            "Status": "exited",
            "Running": false,
            "Paused": false,
            "Restarting": false,
            "OOMKilled": false,
            "Dead": false,
            "Pid": 0,
            "ExitCode": 0,
            "Error": "",
            "StartedAt": "2023-06-02T19:04:55.495093038Z",
            "FinishedAt": "2023-06-02T20:58:27.280446972Z"
        },
        "Image": "sha256:d0e177ece3e530e3ef524973fa0da513c294d0ec5ca1ebd1f7d98bfede55921c",
        "ResolvConfPath": "/var/lib/docker/containers/d5d54dc25c439cd417bd661a3c97c62001f69abc1946a461c2c93911c493db28/resolv.conf",
        "HostnamePath": "/var/lib/docker/containers/d5d54dc25c439cd417bd661a3c97c62001f69abc1946a461c2c93911c493db28/hostname",
        "HostsPath": "/var/lib/docker/containers/d5d54dc25c439cd417bd661a3c97c62001f69abc1946a461c2c93911c493db28/hosts",
        "LogPath": "/var/lib/docker/containers/d5d54dc25c439cd417bd661a3c97c62001f69abc1946a461c2c93911c493db28/d5d54dc25c439cd417bd661a3c97c62001f69abc1946a461c2c93911c493db28-json.log",
        "Name": "/ros_host_container",
        "RestartCount": 0,
        "Driver": "overlay2",
        "Platform": "linux",
        "MountLabel": "",
        "ProcessLabel": "",
        "AppArmorProfile": "unconfined",
        "ExecIDs": null,
        "HostConfig": {
            "Binds": [
                "/dev:/dev:rw",
                "/tmp/.X11-unix:/tmp/.X11-unix:rw",
                "/home/brad/Documents/ROS_Docker/ros_ws:/home/ros:rw"
            ],
            "ContainerIDFile": "",
            "LogConfig": {
                "Type": "json-file",
                "Config": {}
            },
            "NetworkMode": "host",
            "PortBindings": {},
            "RestartPolicy": {
                "Name": "no",
                "MaximumRetryCount": 0
            },
            "AutoRemove": false,
            "VolumeDriver": "",
            "VolumesFrom": null,
            "ConsoleSize": [
                53,
                203
            ],
            "CapAdd": null,
            "CapDrop": null,
            "CgroupnsMode": "host",
            "Dns": [],
            "DnsOptions": [],
            "DnsSearch": [],
            "ExtraHosts": [
                "ros_host:127.0.1.1"
            ],
            "GroupAdd": null,
            "IpcMode": "private",
            "Cgroup": "",
            "Links": null,
            "OomScoreAdj": 0,
            "PidMode": "",
            "Privileged": true,
            "PublishAllPorts": false,
            "ReadonlyRootfs": false,
            "SecurityOpt": [
                "label=disable"
            ],
            "UTSMode": "",
            "UsernsMode": "",
            "ShmSize": 67108864,
            "Runtime": "runc",
            "Isolation": "",
            "CpuShares": 0,
            "Memory": 0,
            "NanoCpus": 0,
            "CgroupParent": "",
            "BlkioWeight": 0,
            "BlkioWeightDevice": [],
            "BlkioDeviceReadBps": [],
            "BlkioDeviceWriteBps": [],
            "BlkioDeviceReadIOps": [],
            "BlkioDeviceWriteIOps": [],
            "CpuPeriod": 0,
            "CpuQuota": 0,
            "CpuRealtimePeriod": 0,
            "CpuRealtimeRuntime": 0,
            "CpusetCpus": "",
            "CpusetMems": "",
            "Devices": [],
            "DeviceCgroupRules": null,
            "DeviceRequests": null,
            "MemoryReservation": 0,
            "MemorySwap": 0,
            "MemorySwappiness": null,
            "OomKillDisable": false,
            "PidsLimit": null,
            "Ulimits": null,
            "CpuCount": 0,
            "CpuPercent": 0,
            "IOMaximumIOps": 0,
            "IOMaximumBandwidth": 0,
            "MaskedPaths": null,
            "ReadonlyPaths": null
        },
        "GraphDriver": {
            "Data": {
                "LowerDir": "/var/lib/docker/overlay2/84aac4a21d23a1eadc4b299b991ef5310fb76ca7838862c3fe96be04b48276e8-init/diff:/var/lib/docker/overlay2/ehi01rxf9psji3wdqh0ceh4l2/diff:/var/lib/docker/overlay2/hz354wg6wvqnnq4hkkim5i2he/diff:/var/lib/docker/overlay2/rkoxnsot1rjmkqzjznkne212u/diff:/var/lib/docker/overlay2/qhhufik40l2u3sbg3g3bekh7k/diff:/var/lib/docker/overlay2/wkawb3bz67kf5w2w3tb22pndy/diff:/var/lib/docker/overlay2/6c9pq3knt3htqduczp5e0zpaw/diff:/var/lib/docker/overlay2/cm18ircdncmc898dhsjujst6p/diff:/var/lib/docker/overlay2/xdpt9aurjd7zs3aj27gfu28qg/diff:/var/lib/docker/overlay2/z6763fohr2y46yava6mwkyvhz/diff:/var/lib/docker/overlay2/ataomfrks99j5voyt076yvjnx/diff:/var/lib/docker/overlay2/7c7prvcl9o2pb9zjbesxxen39/diff:/var/lib/docker/overlay2/cfm9k0u58fmokb51h4bozlkyy/diff:/var/lib/docker/overlay2/n3blum7x2af46pn2p1cckay42/diff:/var/lib/docker/overlay2/laar7nipcxj7f10mf56ugnspj/diff:/var/lib/docker/overlay2/6axou0lzc37eqh7weh3l1aonf/diff:/var/lib/docker/overlay2/yo24sspq5wmrcmt7opcjt9y05/diff:/var/lib/docker/overlay2/xrbl7tub5majkcunf3wdezuew/diff:/var/lib/docker/overlay2/pnlfdbqh47qzjy5y3gh10zd5v/diff:/var/lib/docker/overlay2/1c117fda1704d91763f47ee084b86d64658f24c0a7b1fdd998c068dae99147d3/diff",
                "MergedDir": "/var/lib/docker/overlay2/84aac4a21d23a1eadc4b299b991ef5310fb76ca7838862c3fe96be04b48276e8/merged",
                "UpperDir": "/var/lib/docker/overlay2/84aac4a21d23a1eadc4b299b991ef5310fb76ca7838862c3fe96be04b48276e8/diff",
                "WorkDir": "/var/lib/docker/overlay2/84aac4a21d23a1eadc4b299b991ef5310fb76ca7838862c3fe96be04b48276e8/work"
            },
            "Name": "overlay2"
        },
        "Mounts": [
            {
                "Type": "bind",
                "Source": "/dev",
                "Destination": "/dev",
                "Mode": "rw",
                "RW": true,
                "Propagation": "rprivate"
            },
            {
                "Type": "bind",
                "Source": "/home/brad/Documents/ROS_Docker/ros_ws",
                "Destination": "/home/ros",
                "Mode": "rw",
                "RW": true,
                "Propagation": "rprivate"
            },
            {
                "Type": "bind",
                "Source": "/tmp/.X11-unix",
                "Destination": "/tmp/.X11-unix",
                "Mode": "rw",
                "RW": true,
                "Propagation": "rprivate"
            }
        ],
        "Config": {
            "Hostname": "ros_host",
            "Domainname": "",
            "User": "1000:1000",
            "AttachStdin": false,
            "AttachStdout": false,
            "AttachStderr": false,
            "Tty": true,
            "OpenStdin": true,
            "StdinOnce": false,
            "Env": [
                "DISPLAY=:0",
                "QT_X11_NO_MITSHM=1",
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin"
            ],
            "Cmd": [
                "/bin/bash"
            ],
            "Image": "ros_host",
            "Volumes": null,
            "WorkingDir": "/home/ros",
            "Entrypoint": null,
            "OnBuild": null,
            "Labels": {
                "org.opencontainers.image.ref.name": "ubuntu",
                "org.opencontainers.image.version": "20.04"
            }
        },
        "NetworkSettings": {
            "Bridge": "",
            "SandboxID": "94f374ee1feaf9ffb30b46db69a2168116c2e775d2f98279302640c17e23b63b",
            "HairpinMode": false,
            "LinkLocalIPv6Address": "",
            "LinkLocalIPv6PrefixLen": 0,
            "Ports": {},
            "SandboxKey": "/var/run/docker/netns/default",
            "SecondaryIPAddresses": null,
            "SecondaryIPv6Addresses": null,
            "EndpointID": "",
            "Gateway": "",
            "GlobalIPv6Address": "",
            "GlobalIPv6PrefixLen": 0,
            "IPAddress": "",
            "IPPrefixLen": 0,
            "IPv6Gateway": "",
            "MacAddress": "",
            "Networks": {
                "host": {
                    "IPAMConfig": null,
                    "Links": null,
                    "Aliases": null,
                    "NetworkID": "8bce69e66b65a905c2ecb6ff8e80ff482dc55f6a582e2d47f13c94383c6c4c3c",
                    "EndpointID": "",
                    "Gateway": "",
                    "IPAddress": "",
                    "IPPrefixLen": 0,
                    "IPv6Gateway": "",
                    "GlobalIPv6Address": "",
                    "GlobalIPv6PrefixLen": 0,
                    "MacAddress": "",
                    "DriverOpts": null
                }
            }
        }
    }
]