Today I Learned

2024-09-12 How to translate text from clipboard buffer using translate-shell. Install it, then run a command:
```
pbpaste | trans -b -no-autocorrect -target en
```

2024-08-21 How to download subtitles for a Youtube video:

yt-dlp --skip-download --write-auto-subs --convert-subs srt https://youtube-url-here

2024-08-14 ffprobe is like identify command, but for for video files - it shows video resolution, video and audio codecs, duration and lots of other info:

ffprobe The.Holy.Mountain.1973.REMASTERED.720p.BluRay.999MB.HQ.x265.10bit-GalaxyRG.mkv 2>&1 | grep -Ei '(duration|stream.*video):'
  Duration: 01:53:35.58, start: 0.000000, bitrate: 1213 kb/s
  Stream #0:0: Video: hevc (Main 10), yuv420p10le(tv), 1280x544 [SAR 408:409 DAR 960:409], 23.98 fps, 23.98 tbr, 1k tbn (default)

2024-08-07 How to mount Tailscale drive on Linux:

sudo apt-get install -y davfs2
mkdir ~/ts-drive
# replace mydomain.com/mylaptop/docs with your-tailnet/your-host/drive-name:
sudo mount.davfs http://100.100.100.100:8080/mydomain.com/mylaptop/docs ~/ts-drive -o uid=$(id -u),gid=$(id -g),noexec,nosui

2024-07-05 aggregate: a command to join adjacent network prefixes into a single one. For example how to shorten the Github Actions IPv4 subnets list:

> curl -sSf https://api.github.com/meta | jq -r .actions[] | grep -v :: | wc -l
3738
> curl -sSf https://api.github.com/meta | jq -r .actions[] | grep -v :: | aggregate -q | wc -l
2499

2024-06-03 In Tailscale, a node can advertise custom routes, so you can route the traffic to the particular subnets via this node without using it as an exit node. In this example I route all Google subnets, because I want to access Youtube Premium from an unsupported country:
```
tailscale up --advertise-routes "$(curl https://www.gstatic.com/ipranges/goog.json | jq -r .prefixes[].ipv4Prefix | grep -v null | grep -Ev '^8\.8\.' | tr "\n" "," | sed 's/,$//')"
```

2024-03-05 How to tail logs from multiple pods/containers/apps in a K8s namespace:

kubectl -n MY_NS logs -f --max-log-requests 20 --tail 0 -l 'app in (app1,app2,...)' --all-containers

2024-01-31 Dump Memcached keys with memcdump (install libmemcached-tools package on Ubuntu and libmemcached on RedHat-based systems):
```
memcdump --server=127.0.0.1:11211
```
2023-12-28 How to find where are executable files are located after gem install ...:
```
gem environment | grep 'EXECUTABLE DIRECTORY'
```

2023-12-13 How to set remote IP in Nginx log to X-Real-IP header if the request is proxied via Cloudflare:

( echo "real_ip_header CF-Connecting-IP;"; for URL in https://www.cloudflare.com/ips-v{4,6}/; do curl -sSf  | sed -E 's/^(.*)$/set_real_ip_from \1;/' ; echo ; done ) | tee /etc/nginx/conf.d/cloudflare.conf

then restart or reload Nginx.

2023-11-28 How to find a process listening a port without netstat or ss (source):
```
fuser 7000/tcp
```

2023-11-13 uBlock Origin rule to hide Instagram suggested users:

www.instagram.com##button>span:has-text(/Switch/):nth-ancestor(10)

2023-10-27 How to change the limits for a running process (source):

prlimit --pid 55555 --nofile=1000000:1000000
# make sure the limits have changed:
grep 'Max open files' /proc/55555/limits

2023-10-23 Remove shell color/ANSI codes from text (source):
```
sed "s,\x1B\[[0-9;]*[a-zA-Z],,g"
```
2023-10-17 How to check a ZIP file integrity:
```
zip -T file.zip
# or:
unzip -t file.zip
```

2023-09-19 How to run a command on Mac wakeup (I use it to reconnect to my VPN). Source. First, you need to install Sleepwatcher via Homebrew, and run it as a service, then create shell script named ~/.wakeup, which will be execute on wakeup:

brew install sleepwatcher
brew services start sleepwatcher
brew services | grep sleepwatcher # to make sure the service is running
# now create ~/.wakeup as you usually create shell scripts, starting with #!/bin/bash
chmod +x create ~/.wakeup # make sure it's executable
# to test it, put your Mac to sleep:
pmset sleepnow
# then wake it up and see if your script was executed

2023-09-12 How to trace network calls for a process and all it’s forks/children:
```
strace -f -e trace=network -s 10000 -p $(pgrep -f PROCESS_NAME -d,)
```
2023-09-07 How to print SSH options for a particular host after evaluating config files (SSH dry run, of sorts), source:
```
ssh -G hostname
```
2023-08-25 List files in Alpine APK package (source):
```
apk info -L libc6-compat
```
2023-08-22 To change default time format from AM/PM to 24h on Ubuntu, save the following line in your .bashrc or .bash_profile:
```
export LC_TIME="C.UTF-8"
```

2023-08-22 How to make UFW start on system boot (tested on Ubuntu 20.04, source):

sed -i '/^Before=.*/a After=netfilter-persistent.service' /lib/systemd/system/ufw.service
# reboot, then make sure UFW is enabled:
ufw status
  Status: active

2023-07-19 Command to show Consul cluster members health:
```
consul operator autopilot state
```
2023-06-06 Git command to checkout previous branch - use dash as a branch name, like in cd command:
```
git checkout -
```
2023-05-29 A command to extract images from EPUB file:
```
unzip mybook.epub *.jpg *.jpeg *.png *.gif
```
2023-05-16 How to show details about processes - children of a specific process:
```
pgrep -P 1 -f myprocess | xargs ps -f -p
```
2023-05-10 TIL about tmutil status and made a tiny command line tool to show Time Machine backup progress: https://gist.github.com/haron/58a156d83527bbe1e450aedc7b5c0642

2023-04-28 Percent sign should be escaped in a crontab file (source), for example:

* * * * * date +%Y-%m-%d # won't work as expected
* * * * * date +\%Y-\%m-\%d # will work as expected
* * * * * date -I # will work even better

2023-04-20 How to remove image background using open-source rembg tool:

# python 3.8, 3.9 or 3.10 is required
pip install rembg
rembg i input.jpg output.png

2023-04-20 Command sort -V will sort version numbers:
```
> printf '1.0.11\n1.0.9' | sort -V
1.0.9
1.0.11
```

2023-03-31 How to remove K8s PersistentVolume, when the removing process got stuck in a Terminating state (source):

kubectl edit pv PV_NAME
### remove the following block:
# finalizers:
#  -  kubernetes.io/pv-protection

# then remove the volume:
kubectl delete pv PV_NAME --grace-period=0 --force

2023-03-28 How to fix sudo on my Mac after messing up /etc/pam.d/sudo config file: copy the file to your home directory, edit it, then copy it back with Finder (source).
2023-03-23 Command envsubst replaces references to environment variables with their values. Example:
```
printf 'some\n/Users/haron\ntext\n' | envsubst
```
2023-03-23 How to remove a node from Consul when even force-leave doesn’t help (source):
```
curl -XPUT -d '{"Node":"NODE_NAME"}'  http://NODE_IP:8500/v1/catalog/deregister
```
2023-03-10 Orphaned uWSGI worker processes may consume 100% CPU per worker, unless you remove --master option. Github issue.
2023-03-09 HTML <input> element validation pattern: https://developer.mozilla.org/en-US/docs/Web/HTML/Attributes/pattern

2023-02-12 Supervisord has its own setting to set process’ max open files limit (thanks to this post, now I know it too):

[supervisord]
...
minfds=100000;

To see limits for a running process, show should get its PID and see /proc/PID/limits:

# supervisorctl status
my_process        RUNNING   pid 23754, uptime 0:08:18

# grep 'open files' /proc/23754/limits
Max open files            100000              100000              files

2023-02-09 High quality thumbnails in Python using Pillow library:

from PIL import Image, ImageEnhance

im = Image.open("img.jpg")
im.thumbnail((600, 600))  # max thumbnail size in pixels
enhancer = ImageEnhance.Sharpness(im)
im = enhancer.enhance(2.0)
im.save("tn.jpg", "JPEG", quality="web_medium")

2023-02-09 How to install dig on Alpine Linux:
```
apk add bind-tools
```
2023-02-08 How to install telnet on Alpine linux:
```
apk add busybox-extras
```
2023-02-08 How to get Consul cluster leader:
```
curl localhost:8500/v1/status/leader
```