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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