Cheat Sheet

Useful bash commands and snippets.

apt

Install specific package version

apt-cache policy kubelet
apt-get install kubelet=1.13.4-00

Hold version

apt-mark hold kubelet kubeadm kubectl

Remove hold version

apt-mark unhold kubelet kubeadm kubectl

crontab

List crontab for all users

for user in $(cut -f1 -d: /etc/passwd); do crontab -u $user -l; done

du

Hidden files

du -sch .[!.]* * |sort -h

Sort by size

du -hsc * |sort -h

ncurses interface

sudo apt install ncdu
ncdu

find

find and du -hsc

find . \
  -name "*.txt" \
  -maxdepth 2 \
  -type d \
  -exec du -csh --block-size=1M {} \;

find and rm

find . -name "server.log-2018*" \
  -print0 | xargs -0 rm -f

Find and sed

find . -type f -print0 | xargs -0 sed -i 's/OLD/NEW/g'

Tools

fzf

grep

Sort by second column:

grep -air "count-" file-name* |sort -k2

Hard drive management

List all hard drives and partitions:

sudo lsblk -o NAME,FSTYPE,SIZE,MOUNTPOINT,LABEL

journalctl

Get all logs

Get 20 most recent:

journalctl -n 20

Get process logs

journalctl -u kubelet

Processes management

Check if process is running

#!/bin/bash
service=mongod

if (( $(ps -ef | grep -v grep | grep $service | wc -l) > 0 ))
then
  echo "$service is running!!!"
else
  /etc/init.d/$service start
fi

Swap management

Create swap partition

sudo /bin/dd if=/dev/zero of=/var/swap.0 bs=1M count=1024
sudo /sbin/mkswap /var/swap.0
sudo /sbin/swapon /var/swap.0
echo "/var/swap.0 swap swap defaults 0 0" >> /etc/fstab

Replace 1024 with your desired swap size in MB.

Disable swap

sudo swapoff -a

systemctl

Check if process is enable

systemctl is-enabled PROCESS-NAME-HERE

List all services

systemctl list-units --type service --all

telnet

Client close connection

Input ctrl+]

Then execute: 

close

wget

Backup entire website.

wget \
     --recursive \
     --no-clobber \
     --page-requisites \
     --html-extension \
     --convert-links \
     --restrict-file-names=windows \
     --domains devops.buzz \
     --no-parent \
         https://www.devops.buzz/public/

References

https://www.linuxjournal.com/content/downloading-entire-web-site-wget

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