container-runtime-security

A reference guide to protecting containers, which package applications and their dependencies so they can run in isolated environments.

In plain words
What is it for?
Use it when configuring namespaces, resource limits, Linux capabilities, seccomp filters, AppArmor or SELinux rules, and user namespaces.
Why use it?
It explains which Linux controls limit a container's processes, resources, system calls, files, and privileges.

Skill for Claude CodeCodex

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add skills/hermeticormus/libresecops-claude-code/container-runtime-security
Any agent
npx skills add HermeticOrmus/LibreSecOps-Claude-Code --skill container-runtime-security
Clone the repo
git clone --depth 1 https://github.com/HermeticOrmus/LibreSecOps-Claude-Code

Made for: Claude Code, Codex.

Per session 0 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,744 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 1 finding. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00000 $0.02744
Opus 5 $0.00000 $0.01372
Sonnet 5 $0.00000 $0.00549
Haiku 4.5 $0.00000 $0.00274

Measured 2d ago against content hash cdc3dd6041ea, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

container-runtime-security scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Makes network callslowCapability

Not a fault in itself. Listed so you know the mod talks to something, and to what.

--health-cmd "wget -qO- http://localhost:8080/health || exit 1" \
plugins/container-security/skills/container-runtime-security/SKILL.md · 279 lines

How it starts

The opening of the file, as written. The whole thing — 279 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Container Runtime Security

Runtime isolation mechanisms, Linux capabilities, seccomp profiles, AppArmor, and namespace configuration for containers.

Knowledge Base

Linux Kernel Features Used by Containers

Containers are not a kernel primitive. They are a userspace abstraction built on real kernel features:

Feature Purpose Container Impact
Namespaces Isolation of system resources (PID, NET, MNT, UTS, IPC, USER, CGROUP) Each container gets its own view of processes, network, filesystem mounts
cgroups Resource limiting and accounting (CPU, memory, I/O, PIDs) Prevents a container from consuming all host resources
Capabilities Fine-grained subdivision of root privileges (37 capabilities in Linux) Containers can run as "root" but without dangerous capabilities
Seccomp System call filtering (BPF-based) Blocks dangerous syscalls like mount, reboot, kexec_load
AppArmor/SELinux Mandatory Access Control (MAC) Restricts file access, network operations, capabilities
User namespaces Map container UID 0 to unprivileged host UID Container "root" is not host root

Linux Capabilities Breakdown

Docker drops most capabilities by default, keeping only these 14:

CHOWN, DAC_OVERRIDE, FOWNER, FSETID, KILL, SETGID, SETUID, SETPCAP,
NET_BIND_SERVICE, NET_RAW, SYS_CHROOT, MKNOD, AUDIT_WRITE, SETFCAP

Dangerous capabilities to NEVER add:

Capability Risk
SYS_ADMIN Near-complete root access. Allows mounting filesystems, using unshare, BPF operations. The "god capability."
SYS_PTRACE Trace any process. Can inject code into other containers sharing a PID namespace.
SYS_RAWIO Raw I/O port access, can modify kernel memory via /dev/mem.
DAC_READ_SEARCH Bypass file read permissions. Can read any file on mounted filesystems.
NET_ADMIN Full network control. Can modify routing tables, firewall rules, capture traffic.
SYS_MODULE Load kernel modules. Instant host compromise.

Read the full file on GitHub · 279 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 279 lines · 0 tokens per session scan A cdc3dd6041ea

Subscribe to this mod's changes

container-runtime-security is a skill published in the GitHub repository HermeticOrmus/LibreSecOps-Claude-Code (4 stars, last pushed 3mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 2,744 tokens. A static security scan graded it A with 1 finding (makes network calls). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-31.

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