Tracking Docker container status in real time is a common challenge in DevOps. Popular tools like cAdvisor and the default Docker exporter for Prometheus often lack direct metrics for container states, meaning key insights—such as the number of containers that are running, stopped, or inactive—require complex workarounds. This limitation can complicate monitoring and lead to unreliable data.
Before creating docker_container_exporter, I relied on complex Prometheus queries to retrieve container statuses. This often involved calculations based on the last time a container was seen as active, but this approach had a major flaw: if the query time range didn’t match the last activity timestamp precisely, the data could be inaccurate or incomplete. Monitoring container states shouldn’t be this difficult.
With docker_container_exporter, this problem is solved. My tool captures real-time Docker container statuses, providing data on the number of running, stopped, and other container states, all in a Prometheus-compatible format. You can collect these metrics through a standard Prometheus polling process, or use agents like Grafana Alloy to push the data to Prometheus storage or compatible DB servers like Grafana Mimir or Thanos.
Managing environment variables for different environments, such as production and development, is crucial for deploying applications effectively. In this post, I’ll demonstrate how to use Docker Compose with .env files to easily switch between these environments, using the example of setting a DEBUG_LEVEL variable to control application logging.
To start, you’ll need different .env files for each environment:
1. .env (Common configuration)
ENVIRONMENT=prodUBUNTU_VERSION=24.04
This common .env file sets the default ENVIRONMENT to prod (production) and specifies the Ubuntu version. These variables are used across all environments.
2. .env.prod (Production-specific configuration)
DEBUG_LEVEL=ERROR
In the production environment, DEBUG_LEVEL is set to ERROR to minimize logging output and avoid exposing sensitive information.
3. .env.dev (Development-specific configuration)
DEBUG_LEVEL=DEBUG
In the development environment, DEBUG_LEVEL is set to DEBUG to provide detailed logs for troubleshooting and development purposes.
The compose.yaml file is set up to dynamically load the appropriate environment file based on the ENVIRONMENT variable, which can be set either in the shell or in the .env file:
This configuration uses the env_file directive to load the environment-specific file (.env.prod or .env.dev) based on the value of the ENVIRONMENT variable.
If the ENVIRONMENT variable is set in both the .env file and the shell, the value set in the shell will take precedence. This is useful for temporarily overriding the environment setting without modifying the .env file. For example:
Setting the ENVIRONMENT variable in the shell:
exportENVIRONMENT=dev
If you also have ENVIRONMENT=prod set in the .env file, the shell setting will overwrite it, and the development environment settings will be used:
By using .env files and setting the ENVIRONMENT variable in the shell, you have the flexibility to manage environment variables dynamically. This approach simplifies switching between environments and ensures consistent deployment settings, minimizing the risk of configuration errors and improving application reliability.
In this post, I’ll demonstrate how powerful and flexible the .env file can be when setting up a compose.yaml for Docker Compose. This approach allows for easy management of environment variables, making your Docker configurations more dynamic and manageable.
However, to make the variables defined in the .env file available within the Docker container, you need to add a couple of lines to your compose.yaml file:
After updating the compose.yaml file, run the docker compose up command again. This time, you’ll notice that the UBUNTU_VERSION environment variable is now included in the container’s environment:
This is incredibly convenient because maintaining the .env file allows you to easily manage environment variables across different services without modifying the compose.yaml file each time. This example clearly illustrates how powerful and useful it is to use .env files in Docker Compose configurations.
In the modern era of hybrid working environments, securing remote connections is paramount. Windows 11, keeping pace with this need, facilitates the integration of OpenSSH server for a secure remote login, utilizing key-based authentication. This post delineates a step-by-step approach to set up OpenSSH server, manage key-based authentication, and handle service operations seamlessly using PowerShell.
Installing OpenSSH Server using PowerShell
Launch PowerShell as an Administrator.
Execute the following command to install OpenSSH Server:
Add-WindowsFeature -Name OpenSSH.Server
Once installed, you can check the installation with:
Get-WindowsFeature -Name OpenSSH.*
Managing SSH Public Key
For User Access:
Save the public key in C:\Users\<username>\.ssh\authorized_keys.
For Administrator Access:
Save the public key in C:\ProgramData\ssh\administrators_authorized_keys.
SSH-Agent is a background program that handles private key operations. It stores your private keys securely, requiring you to unlock them only once, thus easing the authentication process.
Generating SSH Key using PowerShell
ssh-keygen -t ed25519
Follow the on-screen instructions to specify a path and passphrase for your keys.
For using the stored keys in SSH Agent, just run a SSH client as always:
ssh username@server_address
By following the above-mentioned steps, you not only set up a robust OpenSSH server on Windows 11 but also ensure a secure remote connectivity through key-based authentication.
In a Dockerized environment, one often encounters the need to monitor network traffic. However, one might not always wish to install sniffing tools within the container itself. By diving into the network namespace of the container, one can employ the host’s network packages such as tcpdump, tcpflow, and others, to achieve this without augmenting the container’s environment.
Step 1: Dive into the Container’s Network Namespace
Fetch the SandboxKey, which denotes the container’s network namespace:
Having entered the namespace, you can now utilize the host’s packages.
Using tcpdump:
tcpdump -i <INTERFACE_NAME>-w <OUTPUT_FILE.pcap>
Replace <INTERFACE_NAME> as per requirement (typically eth0 for Docker containers). For tcpdump, <OUTPUT_FILE.pcap> is the desired capture file. For tcpflow, <OUTPUT_DIRECTORY> is where the captured streams will be saved.
Conclusion
By navigating into a Docker container’s network namespace, you can readily use the network tools installed on the host system. This strategy circumvents the need to pollute the container with additional packages, upholding the principle of container immutability.
If you’re using Docker, you might have noticed that over time, logs can accumulate and take up a significant amount of space on your system. This can be a concern, especially if you’re running containers that generate a lot of log data.
To help you avoid this issue, I’m sharing a quick configuration tweak for Docker. By adjusting the daemon.json file, you can limit the size and number of log files Docker retains.
“log-driver”: “json-file”: This ensures Docker uses the default json-file logging driver, which writes log messages in JSON format.
“log-opts”: {…}: This section contains the logging options.
“max-size”: “10m”: Limits the maximum size of each log file to 10MB.
“max-file”: “1”: Restricts Docker to retain only one log file.
By implementing this configuration, you ensure that Docker only keeps a single log file with a maximum size of 10MB. Once the log reaches this size, Docker will rotate it, ensuring that old logs don’t eat up your storage.
To apply this configuration, simply add the above JSON to your daemon.json file, typically located at /etc/docker/daemon.json on Linux systems. After making the change, restart the Docker service.
I hope this tip helps you manage your Docker logs more efficiently. Happy containerizing! ?
Networking issues can be a real headache, especially when dealing with containerized applications. Whether it’s latency, routing problems, DNS resolution, firewall issues, or incomplete ARPs, network problems can significantly degrade application performance. Fortunately, there’s a powerful tool that can help you troubleshoot and resolve these issues: netshoot.
What is Netshoot?
Netshoot is a Docker container equipped with a comprehensive set of networking troubleshooting tools. It’s designed to help you diagnose and fix Docker and Kubernetes networking issues. With a proper understanding of how Docker and Kubernetes networking works and the right tools, you can troubleshoot and resolve these networking issues more effectively.
Understanding Network Namespaces
Before diving into the usage of netshoot, it’s essential to understand a key concept: Network Namespaces. Network namespaces provide isolation of the system resources associated with networking. Docker uses network and other types of namespaces (pid,mount,user, etc.) to create an isolated environment for each container. Everything from interfaces, routes, and IPs is completely isolated within the network namespace of the container.
The cool thing about namespaces is that you can switch between them. You can enter a different container’s network namespace, perform some troubleshooting on its network stack with tools that aren’t even installed on that container. Additionally, netshoot can be used to troubleshoot the host itself by using the host’s network namespace. This allows you to perform any troubleshooting without installing any new packages directly on the host or your application’s package.
Using Netshoot with Docker
Container’s Network Namespace
If you’re having networking issues with your application’s container, you can launch netshoot with that container’s network namespace like this:
$ sudo docker run -it --net container:<container_name> nicolaka/netshoot
Host’s Network Namespace
If you think the networking issue is on the host itself, you can launch netshoot with that host’s network namespace:
$ sudo docker run -it --net host nicolaka/netshoot
Network’s Network Namespace
If you want to troubleshoot a Docker network, you can enter the network’s namespace using nsenter. This is explained in the nsenter section below.
Using Netshoot with Docker Compose
You can easily deploy netshoot using Docker Compose using something like this:
Netshoot includes a wide range of powerful tools for network troubleshooting. Here’s a list of the included packages along with a brief description of each:
apache2-utils: Utilities for web server benchmarking and server status monitoring.
bash: A popular Unix shell.
bind-tools: Tools for querying DNS servers.
bird: Internet routing daemon.
bridge-utils: Utilities for configuring the Linux Ethernet bridge.
busybox-extras: Provides several stripped-down Unix tools in a single executable.
conntrack-tools: Tools for managing connection tracking records.
curl: Tool for transferring data with URL syntax.
dhcping: Tool to send DHCP requests to DHCP servers.
drill: Tool similar to dig.
ethtool: Tool for displaying and changing NIC settings.
file: Tool to determine the type of a file.
fping: Tool to ping multiple hosts.
grpcurl: Command-line tool for interacting with gRPC servers.
iftop: Displays bandwidth usage on an interface.
iperf: Tool for measuring TCP and UDP bandwidth performance.
iperf3: A newer version of iperf.
iproute2: Collection of utilities for controlling TCP/IP networking.
ipset: Tool to manage IP sets.
iptables: User-space utility program for configuring the IP packet filter rules.
iptraf-ng: Network monitoring tool.
iputils: Set of small useful utilities for Linux networking.
ipvsadm: Utility to administer the IP Virtual Server services.
jq: Lightweight and flexible command-line JSON processor.
libc6-compat: Compatibility libraries for glibc.
liboping: C library to generate ICMP echo requests.
ltrace: A library call tracer.
mtr: Network diagnostic tool.
net-snmp-tools: Set of SNMP management tools.
netcat-openbsd: Networking tool known as the “Swiss army knife” of networking.
nftables: Successor to iptables.
ngrep: Network packet analyzer.
nmap: Network exploration tool and security scanner.
nmap-nping: Packet generation and response analysis tool.
nmap-scripts: Scripts for nmap.
openssl: Toolkit for the Transport Layer Security (TLS) and Secure Sockets Layer (SSL) protocols.
py3-pip: Package installer for Python.
py3-setuptools: Python Distutils Enhancements.
scapy: Packet manipulation tool.
socat: Relay for bidirectional data transfer.
speedtest-cli: Command-line interface for testing internet bandwidth.
openssh: OpenSSH client and server.
strace: System call tracer.
tcpdump: Packet analyzer.
tcptraceroute: Traceroute implementation using TCP packets.
tshark: Network protocol analyzer.
util-linux: Miscellaneous system utilities.
vim: Highly configurable text editor.
git: Distributed version control system.
zsh: Unix shell.
websocat: Simple WebSocket client.
swaks: Swiss Army Knife for SMTP.
perl-crypt-ssleay: Perl module for OpenSSL.
perl-net-ssleay: Perl module for using OpenSSL.
With this extensive set of tools, netshoot is a powerful ally in diagnosing and resolving network issues in your Docker and Kubernetes environments. Whether you’re dealing with latency, routing problems, DNS resolution, firewall issues, or incomplete ARPs, netshoot has the tools you need to troubleshoot and fix these issues.
If you’re interested in trying out netshoot for yourself, you can find the project on GitHub at https://github.com/nicolaka/netshoot. It’s a powerful tool that can help you troubleshoot and resolve network issues in your Docker and Kubernetes environments.
In this blog post, we’ll explore how to use Docker and the lightweight HTTP server, Darkhttpd, to serve static files. This setup is particularly useful when you need a simple web server for sharing files or hosting a static website. We’ll also discuss how to use a reverse proxy like Traefik to route external traffic to the Darkhttpd service.
Docker Compose Configuration
Below is the docker-compose.yml file that defines the Darkhttpd service:
The image field specifies the Docker image to use for the service.
The container_name field sets the name of the container.
The restart field configures the restart policy for the container.
The volumes field defines the volume mounts for the service.
The entrypoint field overrides the default entrypoint of the image.
The networks field specifies the networks that the service is connected to.
Setting Up the Service
Create a directory named site in the same directory as the docker-compose.yml file. Place the static files you want to serve in this directory.
Replace your_network, your_ipv4_address, and your_network_name in the docker-compose.yml file with the appropriate values for your setup.
Run the following command to start the Darkhttpd service:
docker-compose up -d
Access the static files by navigating to the IP address specified in the docker-compose.yml file.
Using a Reverse Proxy
To route external traffic to the Darkhttpd service, you can use a reverse proxy like Traefik. Configure the reverse proxy to forward requests to the IP address specified in the docker-compose.yml file.
Conclusion
Using Docker and Darkhttpd to serve static files is a simple and efficient solution for sharing files or hosting a static website. By adding a reverse proxy, you can easily route external traffic to the Darkhttpd service. This setup is ideal for scenarios where you need a lightweight web server without the overhead of a full-fledged web server like Apache or Nginx.
In today’s interconnected world, maintaining the security of your server infrastructure is paramount. One critical point of vulnerability is the SSH (Secure Shell) service, which allows remote administration of servers. Despite using a non-default port, many administrators still find their servers bombarded with brute-force and denial-of-service attacks. To address this challenge, I’ve developed a solution called StealthSSHAccess.
The Problem
Attackers often employ brute force attacks to gain unauthorized access to servers via SSH. Even if you’ve changed the default SSH port, determined attackers can still discover the new port and target it. These attacks can lead to service disruption, unauthorized data access, and potential breaches of sensitive information.
The Solution: StealthSSHAccess
StealthSSHAccess is an innovative approach to managing remote SSH access while mitigating the risks associated with brute-force attacks. Let’s delve into how it works and why it’s an effective solution:
Dynamic Access Control
StealthSSHAccess takes a dynamic and personalized approach to SSH access control. It operates as a smart gateway between potential attackers and your SSH service. Here’s a simplified breakdown of how it functions:
Monitoring for Intent: Instead of directly exposing the SSH port, StealthSSHAccess monitors a non-SSH TCP port for connection attempts. Attackers, unaware of this, can’t target the SSH port directly.
Capture and Response: When an attempt is made on the monitored port, StealthSSHAccess captures the IP address of the requester. This initial connection attempt fails, serving as a signal of intent to access SSH.
Secure Access Window: Based on this signal, StealthSSHAccess temporarily opens the SSH port exclusively for the captured IP address. This allows for a secure connection from that specific source.
Time-Bound Access: Access is granted for a predetermined duration. If SSH access isn’t established within this timeframe, the port is automatically closed for that specific IP. This tightens the window of exposure and bolsters security.
Automatic Closure: If the port remains unused during the allowed time, StealthSSHAccess automatically revokes access and closes the port. A continuous monitoring mechanism controls this process.
Benefits and Features
1. Enhanced Security: By hiding the SSH port from attackers, StealthSSHAccess reduces the attack surface and minimizes exposure to potential threats.
2. Selective Accessibility: With StealthSSHAccess, you control who gains access by simply attempting a connection to a specific port. This provides an additional layer of security.
3. Minimal Configuration: Implementing StealthSSHAccess is easy thanks to its Docker-based deployment. This means you can integrate it seamlessly into your existing system.
4. Persistence Across Restarts: StealthSSHAccess ensures continuity by persisting IP timer information across service interruptions or restarts. This keeps the system aware of pending access requests.
Getting Started with StealthSSHAccess
To deploy StealthSSHAccess, follow these steps:
Requirements: Ensure you have Docker and Docker Compose installed.
Configuration: Set up environment variables using the provided .env file. Customize parameters like LOGLEVEL, IFACE, PORT_TO_MONITOR, and more to match your environment.
Building and Running: Build the images using docker-compose build, and then launch the services with docker-compose up -d.
Data Persistence: IP timer data is stored in the ./data directory, so make sure it’s writable by the Docker user.
Security Note: Be aware that these services run with privileged access due to their interaction with the system’s network configuration. Understand the security implications before deployment.
Conclusion
In the ongoing battle against cybersecurity threats, StealthSSHAccess stands as a beacon of innovative protection for your servers. By intelligently managing SSH access and responding dynamically to legitimate requests, this solution offers heightened security without sacrificing convenience. Whether you’re an administrator or a security-conscious user, consider integrating StealthSSHAccess into your infrastructure to safeguard your servers from the persistent threats of the digital landscape.
To explore the project, access the source code, and learn more about its implementation, visit the StealthSSHAccess GitHub repository. Remember, security is a journey, and with StealthSSHAccess, you’re taking a proactive step toward a more resilient and secure server environment.
ansible-galaxy install oriolrius.install_gotop# change SERVER_IP, for the IP address where you want to deploy gotopansible -i SERVER_IP,-u root -m include_role -a name=oriolrius.install_gotop all