Linux Container Internals: How Containers Work | DevOpsNess

Linux Container Internals: Understanding How Containers Work

Understanding container internals helps with debugging and optimization. This guide covers the fundamentals.

Linux Namespaces #

Containers use namespaces for isolation:

bash.bash

# PID namespace
unshare --pid --fork bash

# Network namespace
ip netns add mynet
ip netns exec mynet bash

# Mount namespace
unshare --mount bash

# User namespace
unshare --user bash

Control Groups (cgroups)#

cgroups limit and account for resources:

bash.bash

# Create cgroup
mkdir /sys/fs/cgroup/memory/mycontainer
echo 100M > /sys/fs/cgroup/memory/mycontainer/memory.limit_in_bytes

# Add process
echo $$ > /sys/fs/cgroup/memory/mycontainer/cgroup.procs

Container Runtime #

bash.bash

# Using runc directly
runc create mycontainer
runc start mycontainer

# Using containerd
ctr run docker.io/library/alpine:latest mycontainer sh

Container Layers #

bash.bash

# Inspect layers
docker inspect myimage | jq '.[0].RootFS.Layers'

# View layer contents
docker history myimage

Best Practices #

Understand namespaces
Know cgroup limits
Minimize layers
Use multi-stage builds
Monitor resources

Conclusion #

Containers use namespaces for isolation and cgroups for resource limits. Understanding these helps with optimization and debugging.

For Linux Container Internals: Understanding How Containers Work, define pre-deploy checks, rollout gates, and rollback triggers before release. Track p95 latency, error rate, and cost per request for at least 24 hours after deployment. If the trend regresses from baseline, revert quickly and document the decision in the runbook.

Keep the operating model simple under pressure: one owner per change, one decision channel, and clear stop conditions. Review alert quality regularly to remove noise and ensure on-call engineers can distinguish urgent failures from routine variance.

Repeatability is the goal. Convert successful interventions into standard operating procedures and version them in the repository so future responders can execute the same flow without ambiguity.