# docker

### Build arm64 image on amd64 host

```javascript
 docker buildx build --platform linux/arm64 -t glitchcrab/ubuntu-debug:latest --output=type=registry .
```


---

### Run commands in container’s network namespace

* get the container's ID from `docker ps`, then use it to get the PID:

`pid=$(docker inspect -f '{{.State.Pid}}' ${container_id})`

* ensure the netns dir exists and then create the required symlink:

```
mkdir -p /var/run/netns/
ln -sfT /proc/<pid>/ns/net /var/run/netns/<container id>
```

* run a command inside the netns:

`ip netns exec <container id> ip a`


---

### Find largest container log files

```javascript
find /var/lib/docker/containers \
    -name '*-json.log' \
    -printf '%s %p\n' \
| sort -nr \
| numfmt --to=iec
```


***

### Check disk usage

```javascript
docker system df
```


***