#Enable Intel integrated GPUs on Linux systems
Several misconfigurations may stop a Linux machine from having access to its integrated Intel GPU devices. Let’s check the most common problems and how to fix them.
#Snippets
#Troubleshoot CORS-related issues on API requests
Cross-Origin Resource Sharing (a.k.a. CORS) is a powerful, and yet misunderstood, web standard for protecting web APIs from abuse. If you’re anything like me, however, you have had your fair share of wasted work hours trying to deal with it from time to time. The concept seems deceptively simple, but the devil is in the details.
#Use iptables to allow only Cloudflare HTTP requests to target your server
If you’re using Cloudflare to protect HTTP endpoints, it might be worth it to block any web traffic that doesn’t come from their servers.
#Basic survival guide and commands for iptables
iptables is a Linux firewall tool that manages packet routing and can block or allow traffic based on rules like a packet’s origin or destination.
#Protect public URLs with ModSecurity for Nginx on a Kubernetes cluster
If you’re using Ingress Nginx to manage public endpoints, ModSecurity is already installed but disabled by default. To enable it, add the following to the ConfigMap ingress-nginx-controller:
#Host publicly accessible web URLs from a home server using a remote proxy
Ideally, you would be able to open ports 80 and 443 of your public IP address and update DNS entries with solutions like ddclient or DNS-O-Matic.
#Issue Let's Encrypt certificates for domains in a Kubernetes cluster
We will use cert-manager to issue HTTPS certificates for domains served publicly by a Kubernetes cluster.
#Pretty-print JSON files using the command line
If you have either Python 2 or 3 installed, use the json.tool module to pretty-print.
#Quick usage examples of "find" on the command line
Search recursively for file names using a regex pattern. Use -name for a case-sensitive search.
#Read Kubernetes metrics-server data using Golang
First, create the metrics API client.
#Receive data from Kubernetes API using curl
Start by running kubectl proxy. This lets us avoid dealing with authentication headers.
#Activate the replica set mode in MongoDB
Start the MongoDB daemon with the --replSet flag.
#List kernel modules installed on a Linux machine
Get a nicely formatted list:
#Test networking performance between two Linux machines
Let’s use iperf to measure networking performance. First, set up a “server” machine.
#Wipe any filesystem data and partitions from devices on Linux
wipefs should work in most cases to clean up filesystems.
#Download files recursively through an FTP connection using wget
Unfortunately, SCP and rsync aren’t always an option to get our files out of a server. When FTP is all we have, wget can still do a pretty good job and won’t re-download files you already have, like a primitive rsync.
#Check a site's downtime with this bash one-liner
During site downtime, the following one-liner prints the current time and tries to access the given URL every 2 seconds. Only the received HTTP headers are shown.
#List running queries in a MariaDB server
mysql -u$MYSQL_USER -p$MYSQL_PASSWORD $MYSQL_DATABASE
SHOW FULL PROCESSLIST;
## OR
mysqladmin -u$MYSQL_USER -p$MYSQL_PASSWORD processlist#Find the biggest files and folders on a Linux server
du -ah / | sort -n -r | head -n 10#How to manually create a Let's Encrypt certificate using Docker and the DNS challenge
docker run -it -v ${PWD}:/etc/letsencrypt --entrypoint="sh" certbot/certbot
certbot certonly -d <domain_name> --manual --preferred-challenges dns#Format a new SSD/HDD for use
# Create the partition
parted --align optimal <raw_device>
mklabel msdos
mkpart primary ext4 0% 100%
quit
# Get the new partition device path
lsblk
# Make the filesystem
mkfs.ext4 <new_partition_device_path>
# Test the partition
mkdir /tmp/partition-test
mount -t ext4 <new_partition_device_path> /tmp/partition-test
# Get the UUID
blkid
# Edit the /etc/fstab to mount partition during boot
UUID=<uuid> /storage ext4 defaults,discard 0 2
## OR, if using XFS
UUID=<uuid> /storage xfs defaults 1 2#Basic shortcuts for navigating the psql command line (PostgreSQL)
psql -h $POSTGRES_HOST -U $POSTGRES_USER $POSTGRES_DB
\du # list all users
\l # list databases
\c # select a database
\d # list tables
\d+ <table_name> # describe table
\dx # list installed extensions
SELECT * FROM pg_available_extensions; # list extensions available on the server
CREATE EXTENSION IF NOT EXISTS <ext_name>; # install an extension
ALTER EXTENSION <ext_name> UPDATE TO 'new_version'; # upgrade an extension#Dump and restore data from MongoDB in Docker
# Create the database dump on your server
docker exec <my_mongodb_container> mongodump --archive=/backups/mongodb-`date +%Y%m%d`.gz --gzip --db <database_name>
# Copy it to your local machine, if needed
scp -r <server_user>@<server_ip>:<remote_backup_path> <local_backup_path>
# Restore it directly into a running Docker container
zcat <backup_path> | docker exec -i <my_mongodb_container> mongorestore --archive --drop#Update URLs in a multisite WordPress installation after a domain change
You will need wp-cli for this.
#Sane defaults for the most common rsync needs
rsync -avhP -e 'ssh -p <optional_server_port>' --info=progress2 <server_user>@<server_ip>:<path_to_be_copied> <destination_path>