Docker Daemon Won't Start on Ubuntu 22.04 – Fix It Now

The 30-Second Fix: Restart & Check Service Status

Before diving into logs or configs, let's make sure Docker's service is actually running. I've seen this trip up a lot of people—Docker can fail silently after an update or reboot.

Open a terminal and run:

sudo systemctl status docker

If you see something like Active: failed (Result: exit-code) or inactive (dead), try restarting it:

sudo systemctl restart docker

Then check again. If that spits back active (running), you're golden. If not, move to the next step. This works about 30% of the time—usually when the daemon just stumbled after an update or the socket got hung.

The 5-Minute Fix: Check Docker Daemon Logs

If a restart didn't stick, the daemon is crashing. Docker keeps its logs in /var/log/daemon.log or /var/log/syslog, but the quickest read is via journalctl. Run this to see the last 20 lines of Docker's fight:

sudo journalctl -u docker.service --no-pager -n 20

Look for common trouble signs:

• "failed to start daemon: Error initializing network controller" – That's usually a Docker bridge or firewall conflict. I've fixed this by resetting Docker's network: sudo systemctl stop docker; sudo rm -rf /var/lib/docker/network; sudo systemctl start docker. Don't worry, this doesn't touch your containers or images—just the network config.
• "could not create default bridge network" – Often from leftover iptables rules. Try sudo iptables -F then sudo iptables -P FORWARD ACCEPT, then restart Docker.
• "permission denied" or "socket: permission denied" – Your user isn't in the docker group. Add yourself: sudo usermod -aG docker $USER, then log out and back in.

If you see "iptables: No chain/target/match by that name", Docker's trying to use iptables but it's not installed. Install it: sudo apt update && sudo apt install iptables. Yes, even on modern Ubuntu, Docker still leans on iptables by default unless you've switched to nftables.

One more thing: check your disk space. Docker won't start if the disk is full. Run df -h—if any partition is at 100%, clear space. I've seen a full /var partition kill Docker silently.

The 15+ Minute Fix: Edit Docker Daemon Configuration

If logs didn't point to a clear cause, your config file is the likely culprit. Docker's main config lives at /etc/docker/daemon.json. If it's missing, that's fine—Docker uses defaults. But if it's present and broken, things get ugly.

Check it with:

sudo cat /etc/docker/daemon.json

Look for these common mistakes:

1. Invalid JSON. Missing commas, extra brackets. Use a JSON validator online or run python3 -m json.tool /etc/docker/daemon.json to check. If it fails, fix the syntax.
2. Conflicting networking options. For example, setting both "bip": "172.17.0.1/16" and "default-address-pools" can cause a conflict. Remove the bip line if you have pools defined.
3. Wrong directory paths. If you set "data-root" to a non-existent path, Docker won't start. Make sure the path exists and is writable: sudo mkdir -p /path/you/set; sudo chown root:root /path/you/set.

If you're running a custom Docker version or rootless Docker, check ~/.config/docker/daemon.json too. I've helped folks who swore they had no config, only to find a broken rootless one in their home directory.

A real-world scenario: I once saw a daemon fail because someone set "exec-opts": ["native.cgroupdriver=systemd"] but the system was using cgroups v1. Cgroups v2 became default in Ubuntu 21.10+. If you're on Ubuntu 22.04 with cgroups v2, the native driver works fine, but if you're on v1, you need "exec-opts": ["native.cgroupdriver=cgroupfs"]. Check your cgroups version: stat -fc %T /sys/fs/cgroup/. If it returns cgroup2fs, you're on v2.

If All Else Fails: Reinstall Docker

This is my nuclear option. Remove Docker completely, then reinstall. Here's the clean command sequence I use:

sudo systemctl stop docker
sudo apt purge docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin
sudo rm -rf /var/lib/docker /var/lib/containerd /etc/docker
sudo apt update
sudo apt install docker-ce docker-ce-cli containerd.io

This wipes all containers and images, so back up anything you need first. After the install, start Docker and test it with sudo docker run hello-world. If that works, you're back in business.

One last tip: if you're behind a corporate proxy, set the proxy in /etc/systemd/system/docker.service.d/http-proxy.conf. Docker ignores system-wide proxy settings sometimes. That's bitten me twice.