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Check if Docker is Installed Using Snap
Snap is an application packaging system by Canonical. It uses a variation on containers to isolate the application. It's preferable not to use this type of installation. If Docker as a Snap is installed, please uninstall and install the Docker Community edition.
To check is Docker is installed as a Snap run the command
$ sudo snap list
Name Version Rev Tracking Publisher Notes
bare 1.0 5 latest/stable canonical✓ base
core20 20221027 1695 latest/stable canonical✓ base
docker 19.03.11 471 latest/candidate canonical✓ -
Is The Docker Daemon Running?
$ sudo docker ps
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?
#systemctl enable docker.service
Created symlink /etc/systemd/system/multi-user.target.wants/docker.service → /usr/lib/systemd/system/docker.service.
# systemctl start docker.service
Are the iptables Rules Configured?
The following commands should look similar to this:
$ sudo iptables -L -t nat
Chain PREROUTING (policy ACCEPT)
target prot opt source destination
DOCKER all -- anywhere anywhere ADDRTYPE match dst-type LOCAL
Chain INPUT (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
DOCKER all -- anywhere !127.0.0.0/8 ADDRTYPE match dst-type LOCAL
Chain POSTROUTING (policy ACCEPT)
target prot opt source destination
MASQUERADE all -- 172.17.0.0/16 anywhere
Chain DOCKER (2 references)
target prot opt source destination
RETURN all -- anywhere anywhere
$ sudo iptables -L
Chain INPUT (policy ACCEPT)
target prot opt source destination
Chain FORWARD (policy DROP)
target prot opt source destination
DOCKER-USER all -- anywhere anywhere
DOCKER-ISOLATION-STAGE-1 all -- anywhere anywhere
ACCEPT all -- anywhere anywhere ctstate RELATED,ESTABLISHED
DOCKER all -- anywhere anywhere
ACCEPT all -- anywhere anywhere
ACCEPT all -- anywhere anywhere
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
Chain DOCKER (1 references)
target prot opt source destination
Chain DOCKER-ISOLATION-STAGE-1 (1 references)
target prot opt source destination
DOCKER-ISOLATION-STAGE-2 all -- anywhere anywhere
RETURN all -- anywhere anywhere
Chain DOCKER-ISOLATION-STAGE-2 (1 references)
target prot opt source destination
DROP all -- anywhere anywhere
RETURN all -- anywhere anywhere
Chain DOCKER-USER (1 references)
target prot opt source destination
RETURN all -- anywhere anywhere
If Empty or no DOCKER Entries, Check:
- If the Docker daemon running?
- If SeLinux enforcing?
# sudo getenforce
Enforcing
a. Disable SeLinux
b. Configure Docker to work properly with SeLinux.
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