From 55dd844f3e6ff5c2524fd30c212ead5de28b9560 Mon Sep 17 00:00:00 2001
From: Michele Cereda <cereda.michele@gmail.com>
Date: Fri, 18 Nov 2022 09:11:30 +0100
Subject: [PATCH] Improved readability

---
 knowledge base/cloud-init.md | 15 +++++++----
 knowledge base/curl.md       | 48 ++++++++++++++++++------------------
 knowledge base/nc.md         | 10 +++++---
 3 files changed, 41 insertions(+), 32 deletions(-)

diff --git a/knowledge base/cloud-init.md b/knowledge base/cloud-init.md
index a971b56..468a072 100644
--- a/knowledge base/cloud-init.md	
+++ b/knowledge base/cloud-init.md	
@@ -23,17 +23,18 @@ cloud-init devel schema --config-file '/tmp/user-data'
 
 # Check the raw logs.
 cat '/var/log/cloud-init.log'
+cat '/var/log/cloud-init-output.log'
 
-# Parse and organize cloud-init.log events by stage.
+# Parse and organize the events in the log file by stage.
 cloud-init analyze show
 
-# Manually run a single cloud-config module onceafter the instance has booted.
+# Manually run a single cloud-config module once after the instance has booted.
 sudo cloud-init single --name 'cc_ssh' --frequency 'always'
 
-# Clean up everything so cloud-init can re-run.
+# Clean up everything so `cloud-init` can run again.
 sudo cloud-init clean
 
-# Re-run all.
+# Re-run everything.
 sudo cloud-init init
 ```
 
@@ -75,11 +76,15 @@ package_reboot_if_required: false
 # https://cloudinit.readthedocs.io/en/latest/topics/examples.html#install-arbitrary-packages
 #
 # docker-ce already depends on docker-ce-cli and containerd.io
-packages:
 packages:
   - docker-ce
   - jq
   - unzip
+
+# Enable and start the service after installation
+runcmd:
+  - systemctl daemon-reload
+  - systemctl enable --now docker.service
 ```
 
 ## Merge 2 or more files or parts
diff --git a/knowledge base/curl.md b/knowledge base/curl.md
index 203da21..9b42b93 100644
--- a/knowledge base/curl.md	
+++ b/knowledge base/curl.md	
@@ -4,63 +4,63 @@
 
 ```sh
 # Send a single GET request and show its output on stdout.
-curl http://url.of/file
+curl 'http://url.of/file'
 
 # Be quiet.
-curl --silent https://www.example.com
-curl -s --show-error https://www.example.com
+curl --silent 'https://www.example.com'
+curl -s --show-error 'https://www.example.com'
 
 # Download files.
-curl http://url.of/file -o path/to/file
-curl -O http://url.of/file1 -O http://url.of/file2
+curl 'http://url.of/file' -o 'path/to/file'
+curl -O 'http://url.of/file1' -O 'http://url.of/file2'
 curl http://url.of/file[1-24]
 
 # Resume downloads.
-curl -C - -o partial_file http://url.of/file
+curl -C - -o 'partial_file' 'http://url.of/file'
 
 # Limit downloads bandwidth.
-curl --limit-rate 1000B -O http://url.of/file
+curl --limit-rate '1000B' -O 'http://url.of/file'
 
 # Follow redirects.
-curl -L http://url.of/file
+curl -L 'http://url.of/file'
 
 # Only fetch HTTP headers from a response.
-curl -I http://example.com
+curl -I 'http://example.com'
 
 # Only return the HTTP status code.
-curl -o /dev/null -w '%{http_code}\n' -s -I http://example.com
+curl -o '/dev/null' -w '%{http_code}\n' -s -I 'http://example.com'
 
 # Send different request types.
-curl --request PUT http://example.com
+curl --request 'PUT' 'http://example.com'
 
 # Specify headers.
-curl http://example.com -H "Content-Type:application/json" http://example.com
+curl 'http://example.com' -H 'Content-Type:application/json' 'http://example.com'
 
 # Skip certificate validation.
-curl --insecure https://example.com
+curl --insecure 'https://example.com'
 
 # Pass certificates for a resource.
-curl --cert client.pem --key key.pem -k https://example.com
-curl --cacert ca.pem https://example.com
+curl --cert 'client.pem' --key 'key.pem' -k 'https://example.com'
+curl --cacert 'ca.pem' 'https://example.com'
 
 # Authenticate.
-curl -u username:password http://url.of/file
-curl -u username:password -O ftp://url.of/file
-curl ftp://username:password@example.com
+curl -u 'username':'password' 'http://url.of/file'
+curl -u 'username':'password' -O 'ftp://url.of/file'
+curl 'ftp://username:password@example.com'
 
 # POST to a form.
-curl -F "name=user" -F "password=test" http://example.com
-curl --data 'name=bob' http://example.com/form
+curl -F 'name=user' -F 'password=test' 'http://example.com'
+curl --data 'name=bob' 'http://example.com/form'
 
 # Send data.
-curl http://example.com -H "Content-Type:application/json" -d '{"name":"bob"}' -X POST
-curl http://example.com -H "Content-Type:application/json" -d @file.json -X POST
+curl 'http://example.com' -H "Content-Type:application/json" -d '{"name":"bob"}' -X 'POST'
+curl … -d @file.json
 
 # Use a proxy.
-curl http://example.com --proxy socks5://localhost:19999
+curl 'http://example.com' --proxy 'socks5://localhost:19999'
 
 # Forcefully resolve a host to a given address.
-curl https://example.com --resolve example.com:443:google.com
+curl 'https://example.com' --resolve 'example.com:443:google.com'
 ```
 
 ## Apply settings to all connections
diff --git a/knowledge base/nc.md b/knowledge base/nc.md
index 7988b79..9c06412 100644
--- a/knowledge base/nc.md	
+++ b/knowledge base/nc.md	
@@ -13,10 +13,14 @@
 ## TL;DR
 
 ```sh
-# Check port 22 on hosts.
+# Check ports on hosts.
 nc -Nnvz 192.168.0.81 22
-parallel -j 0 "nc -Nnvz -w 2 192.168.0.{} 22 2>&1" ::: {2..254} | grep -v "timed out"
+nc -Nvz host.name 443
+
+# List hosts with a specific port open.
+parallel -j 0 "nc -Nnvz -w 2 192.168.0.{} 22 2>&1" ::: {2..254} \
+| grep -v "timed out"
 
 # Wait for a host to be up.
-until nc -Nvz -w 3 pi4.lan 22; do sleep 3; done
+until nc -Nvz -w 3 pi.lan 22; do sleep 3; done
 ```