# Cheat Sheet

## apt

### Install specific package version

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

### Hold version

```bash
apt-mark hold kubelet kubeadm kubectl
```

### Remove hold version

```bash
apt-mark unhold kubelet kubeadm kubectl
```

## crontab

### List crontab for all users

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

## du

### Hidden files

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

### Sort by size

```bash
du -hsc * |sort -h
```

### ncurses interface

```bash
sudo apt install ncdu
ncdu
```

## find

### find and du -hsc

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

### find and rm

```bash
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

{% embed url="<https://github.com/junegunn/fzf>" %}

## grep

Sort by second column:

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

## Hard drive management

List all hard drives and partitions:

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

## journalctl

### Get all logs

Get 20 most recent:

```bash
journalctl -n 20
```

### Get process logs

```bash
journalctl -u kubelet
```

## Processes management

### Check if process is running

```bash
#!/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

```bash
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
```

{% hint style="info" %}
Replace **1024** with your desired swap size in MB.
{% endhint %}

### Disable swap

```bash
sudo swapoff -a
```

## systemctl

### Check if process is enable

```bash
systemctl is-enabled PROCESS-NAME-HERE
```

### List all services

```bash
systemctl list-units --type service --all
```

## telnet

### Client close connection

Input `ctrl+]`

Then execute:&#x20;

```bash
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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