The syntax to run a systemd timer every ten minutes is:
OnCalendar=*-*-* *:00,10,20,30,40,50:00
i.e. run it on the first second (:00) of every 10th minute (00,10,20,30,40,50).
27
Mar
2022
27
Mar
2022
How to use git current branch in bash scripts
# Branch is, for example, "main" export branch=$(git branch --show-current)
27
Mar
2022
Traefik docker container labels for custom port & ALPN certificate
See our previous post Simple Traefik docker-compose setup with Lets Encrypt Cloudflare DNS-01 & TLS-ALPN-01 & HTTP-01 challenges for the general config we’re using to deploy Traefik. This includes the configuration of the alpn certificate resolver.
If you want to automatically connect Traefik to your docker container on a specific port running on the docker container (17029 in this example), use labels like
labels:
- "traefik.enable=true"
- "traefik.http.routers.my-webservice.rule=Host(`subdomain.mydomain.com`)"
- "traefik.http.routers.my-webservice.entrypoints=websecure"
- "traefik.http.routers.my-webservice.tls.certresolver=alpn"
- "traefik.http.services.my-webservice.loadbalancer.server.port=17029"
27
Mar
2022
Recommended PostgreSQL docker-compose service configuration
I use the following docker-compose.yml service:
version: '3.5'
services:
postgres:
image: postgres
restart: unless-stopped
volumes:
- ./pg_data:/var/lib/postgresql/data
environment:
- POSTGRES_PASSWORD=${POSTGRES_PASSWORD}
- POSTGRES_DB=${POSTGRES_DB}
- POSTGRES_USER=${POSTGRES_USER}
With the following .env:
POSTGRES_DB=headscale POSTGRES_USER=headscale POSTGRES_PASSWORD=vah2phuen3shesahc6Jeenaechecee
Using .env has the huge advantage that other services like my backup script can access the configuration in a standardized manner using environment variables.
27
Mar
2022
How I run pg_dump in my docker-compose setup
I have the following docker-compose.yml service:
version: '3.5'
services:
postgres:
image: postgres
restart: unless-stopped
volumes:
- ./pg_data:/var/lib/postgresql/data
environment:
- POSTGRES_PASSWORD=${POSTGRES_PASSWORD}
- POSTGRES_DB=${POSTGRES_DB}
- POSTGRES_USER=${POSTGRES_USER}
With the following .env:
POSTGRES_DB=headscale POSTGRES_USER=headscale POSTGRES_PASSWORD=vah2phuen3shesahc6Jeenaechecee
Given that setup, I run pg_dump like this:
source .env && docker-compose exec postgres pg_dump -U${POSTGRES_USER} > pgdump-$(date +%F_%H-%M-%S).sql 26
Mar
2022
How to connect Synology NAS to Headscale
First, install the Tailscale App using the Synology Package manager. Don’t try to initialize using the UI since this will only work with the commercial tailscale service, not with headscale.
Then login to the NAS using SSH (I’m using the admin account) and run sudo su to run
You should see the following shell prompt:
ash-4.4#
Now you can initialize tailscale using the tailscale command similar to our previous post How to connect tailscale to headscale server on Linux. In my case, I needed to use the --reset flag in order for the command to work.
tailscale up --reset --login-server https://headscale.mydomain.com --authkey ... --accept-routes
This will login to your server just like the normal (non-synology) tailscale client does.
26
Mar
2022
How to generate filename containing date & time on the command line
The following snippet is useful for backups to generate a unique yet sortable filename containing both date and time:
mysqldump-$(date +%F_%H-%M-%S).sql
This generates filenames like
mysqldump-2022-03-26_20-47-01.sql
which are compatible with both Windows and Linux as they don’t contain special characters like :
25
Mar
2022
How to delete all files containing a specific string using ack-grep (ag)
Based on our previous post How to list filenames containing a specific string using ack-grep (ag) this example shows how to delete all files in the current directory containing the string 403 Forbidden.
For example, in order to list filenames containing the string 403 Forbidden, use
ag -0 -l "403 Forbidden" | xargs -0 rm -v
Using ag -0 is neccessary to handle filenames containing spaces correctly.
25
Mar
2022
How to list filenames containing a specific string using ack-grep (ag)
Use ag -l to list only filenames that contain the given string.
For example, in order to list filenames containing the string 403 Forbidden, use
ag -l "403 Forbidden"
23
Mar
2022
How to list directory with millions of files
ls -1U
22
Mar
2022
ufw: How to allow traffic to all ports on specific interface
sudo ufw allow in on tailscale0 to any
This will allow any traffic (including routed traffic, if packet forwarding is enabled) coming from the tailscale0 interface.
21
Mar
2022
How to install tailscale on Ubuntu
In order to instal tailscale, on any Ubuntu version, you can use the official tailscale install command:
sudo apt -y install curl apt-transport-https curl -fsSL https://tailscale.com/install.sh | sh
21
Mar
2022
How to install Xen guest utilities on Ubuntu
On Ubuntu 22.04, this package is not available any more and the best way to install it that is known to me at the moment is to use the guest tools ISO.
Install the package using
sudo apt -y install xe-guest-utilities
Now reboot, which will automatically start the management agent service:
sudo reboot
21
Mar
2022
How to get Jitsi meet list of participants using Tapermonkey script
Use this code in Javascript:
APP.conference.listMembers()
If no members are present, this will simply be an empty list:
> APP.conference.listMembers() []
But if there is another participant, it will show some info:
> APP.conference.listMembers()
[ci]
0: ci {_jid: '[email protected]/b009ae10', _id: 'b009ae10', _conference: nd, _displayName: 'Foo', _supportsDTMF: false, …}
length: 1
21
Mar
2022
How to autojoin Jitsi Meet meeting using Tapermonkey script
This code clicks the join button:
document.querySelector(".prejoin-preview-dropdown-container div[role='button']").click()By using the correct @match, you can activate this only for a specific conference:
Complete script:
// ==UserScript==
// @name AutojoinJitsiMeet
// @namespace http://tampermonkey.net/
// @version 0.1
// @description ?
// @author You
// @match https://meet.jit.si/TestAutoJoin
// @icon https://www.google.com/s2/favicons?sz=64&domain=tampermonkey.net
// @grant none
// ==/UserScript==
(function() {
'use strict';
document.querySelector(".prejoin-preview-dropdown-container div[role='button']").click()
})();
21
Mar
2022
NodeJS typescript simple auto-reload on file change
First install ts-node-dev:
npm i --save-dev ts-node-dev
Then add
"start": "./node_modules/.bin/tsnd --respawn app.ts"
to package.json in the scripts section, example:
{
"name": "myapp-backend",
"version": "1.0.0",
"description": "To make it easy for you to get started with GitLab, here's a list of recommended next steps.",
"main": "index.js",
"scripts": {
"build": "./node_modules/.bin/tsc -b tsconfig.json",
"start": "./node_modules/.bin/tsnd --respawn app.ts"
}
/* ... */
}
21
Mar
2022
A simple systemd service autoinstall script
I use this in git repositories to ease the deployment process
#!/bin/bash
# This script installs and enables/starts a systemd service
# It also installs the service file
export NAME=MyService
cat >/etc/systemd/system/${NAME}.service <<EOF
# TODO Copy & paste the systemd .service file here
EOF
# Enable and start service
systemctl enable --now ${NAME}.service
The following example automatically installs a docker-compose systemd .service:
#!/bin/bash
# This script installs and enables/starts a systemd service
# It also installs the service file
export NAME=MyService
cat >/etc/systemd/system/${NAME}.service <<EOF
[Unit]
Description=${NAME}
Requires=docker.service
After=docker.service
[Service]
Restart=always
User=root
Group=docker
WorkingDirectory=$(pwd)
# Shutdown container (if running) before unit is being started
ExecStartPre=$(which docker-compose) -f docker-compose.yml down
# Start container when unit is started
ExecStart=$(which docker-compose) -f docker-compose.yml up
# Stop container when unit is stopped
ExecStop=$(which docker-compose) -f docker-compose.yml down
[Install]
WantedBy=multi-user.target
EOF
# Enable and start service
systemctl enable --now ${NAME}.service
16
Mar
2022
Fullscreen camera view using libcamera-vid
libcamera-vid --width 1920 --height 1080 -f -t 10000000000
-t 10000000000 means to run for 10000000000 milliseconds (almost 4 months)
14
Mar
2022
How to fix raspistill ERROR: the system should be configured for the legacy camera stack
Problem:
While trying to capture an image using raspistill, you see the following error message
ERROR: the system should be configured for the legacy camera stack
and no image is being produced
Solution 1 (recommended): Use libcamera
Recent versions of Raspbian use libcamera instead of the broadcom legacy camera API. You can capture an image using libcamera-still similarly to raspistill:
libcamera-still -o test.jpg
Solution 2: Enable legacy camera API
If you absolutely need raspistill specifically to work, you can still enable the legacy camera API using rpi-config:
sudo raspi-config
Go to:
- 3 Interface Config
- I1 Legacy Camera
and choose Yes to enable the legacy camera API.
14
Mar
2022
Raspberry Pi libcamera VLC livestreaming (1920×1080)
On the Pi, run
libcamera-vid -t 0 --width 1920 --height 1080 --codec h264 --inline --listen -o tcp://0.0.0.0:8888
On the client, run
vlc tcp/h264://192.168.1.185:8888/
where 192.168.1.185 is the IP address of the Raspberry Pi.