Tag: linux

Run shell script before shutdown – linux

before_shutdown.sh

#!/bin/bash
#remove file older than 7 days
find /var/log -name "*.log" -type f -mtime +7

#test
touch "/opt/before_shutdown_tmp_file_$(date +%s)"
  • Create systemd service
echo '[Unit]
Description=before_shutdown

[Service]
ExecStart=/bin/true
Type=oneshot
RemainAfterExit=true
ExecStop=/opt/before_shutdown.sh

[Install]
WantedBy=multi-user.target' > /etc/systemd/system/before_shutdown.service
systemctl daemon-reload

systemctl enable before_shutdown

systemctl start before_shutdown

https://unix.stackexchange.com/questions/39226/how-to-run-a-script-with-systemd-right-before-shutdown

raspberry pi fan on/off automation based on cpu temp

Note : This does not work because IO pins does not enough power to run fan.

fan.py

import RPi.GPIO as GPIO
from time import sleep
import sys

GPIO.setwarnings(False)
GPIO.setmode(GPIO.BOARD)
GPIO.setup(8, GPIO.OUT, initial=GPIO.LOW) 

if sys.argv[1] == "on":
 GPIO.output(8, GPIO.HIGH)
 print("on")
else:
 GPIO.output(8, GPIO.LOW)
 print("off")

Dockerfile

FROM python:slim-buster
WORKDIR /fan
RUN apt update && \
    apt install python-rpi.gpio python3-rpi.gpio -y 
COPY fan.py .

Docker build

docker build -t fan .

Docker run command switch on

docker run -it --device /dev/gpiomem fan python2 fan.py on

Docker run command switch off

docker run -it --device /dev/gpiomem fan python2 fan.py off

fan.sh

#!/bin/bash

cpu=$(</sys/class/thermal/thermal_zone0/temp)

cpu_temp=$(echo "$cpu/1000" | /usr/bin/bc)
echo $cpu_temp

if(("cpu_temp" >= "65"))
then
echo "more 65 on fan"
docker run -it --device /dev/gpiomem fan python2 fan.py on
else
echo "less 65 off fan"
docker run -it --device /dev/gpiomem fan python2 fan.py off
fi

More: https://raspberrypihq.com/making-a-led-blink-using-the-raspberry-pi-and-python/

https://stackoverflow.com/questions/48441737/docker-error-no-access-to-dev-mem-try-running-as-root

Mount cifs/samba share inside container

#Dockerfile
FROM ubuntu
RUN apt update -y
RUN apt install  cifs-utils -y

docker build -t cifs .
docker run -it --cap-add SYS_ADMIN --cap-add DAC_READ_SEARCH   -cap-add NET_BIND_SERVICE cifs bash
#centos with privileged (working)

docker run --privileged -it --cap-add SYS_ADMIN --cap-add DAC_READ_SEARCH --cap-add NET_BIND_SERVICE centos bash
mount -t cifs -o username=a,password=a //192.168.0.228/public /mnt
mount -t cifs -o username=a,password=a //192.168.0.228/public /mnt
mount -t cifs -o username=a,password=a,ro,domain=WORKGROUP //192.168.0.228/public /a -v

Tmux , Screen, Nohup, – Run command in background

Why?
– Run process in background
– Run database backup in background

Tmux:

#List
tmux ls

#Start session
tmux new -s mysession

#Reconnect  
tmux a -t session_name

#Disconnect
ctrl + b + D


#Reconnect to 0 session
tmux a -t 0

More : https://tmuxcheatsheet.com

Screen :

#List
screen -ls

#Named session
screen -A -m -d -S session_name command

#Reconnect to named session
screen -r session_name 

#Disconnect
CTRL + a + d

https://gist.github.com/jctosta/af918e1618682638aa82

Nohup:

Nohup command &

It’s create nohup.out file in same directory with all command logs

https://www.thegeekdiary.com/nohup-command-examples-runs-a-command-that-keeps-running-after-you-log-out/

Jobs:

jobs
fg
bg

https://tldp.org/LDP/abs/html/x9644.html

Strings command in linux

strings /lib64/libc.so.6 |grep GLIBC

strings /bin/ls


Usage: strings [option(s)] [file(s)]
 Display printable strings in [file(s)] (stdin by default)
 The options are:
  -a - --all                Scan the entire file, not just the data section [default]
  -d --data                 Only scan the data sections in the file
  -f --print-file-name      Print the name of the file before each string
  -n --bytes=[number]       Locate & print any NUL-terminated sequence of at
  -<number>                   least [number] characters (default 4).
  -t --radix={o,d,x}        Print the location of the string in base 8, 10 or 16
  -w --include-all-whitespace Include all whitespace as valid string characters
  -o                        An alias for --radix=o
  -T --target=<BFDNAME>     Specify the binary file format
  -e --encoding={s,S,b,l,B,L} Select character size and endianness:
                            s = 7-bit, S = 8-bit, {b,l} = 16-bit, {B,L} = 32-bit
  -s --output-separator=<string> String used to separate strings in output.
  @<file>                   Read options from <file>
  -h --help                 Display this information
  -v -V --version           Print the program's version number
strings: supported targets: elf64-x86-64 elf32-i386 elf32-iamcu elf32-x86-64 a.out-i386-linux pei-i386 pei-x86-64 elf64-l1om elf64-k1om elf64-little elf64-big elf32-little elf32-big pe-x86-64 pe-bigobj-x86-64 pe-i386 plugin srec symbolsrec verilog tekhex binary ihex