====== Commands ======
===== badblocks =====
<code bash>badblocks -vfws /dev/sdx</code>
  * verbose
  * force
  * write
  * show progress

===== tail =====
vypis logu v realnem case
<code bash>tail -f /soubor</code>
vyber ze souboru
<code bash>tail -f /soubor | grep --line-buffered hledaneslovo</code>
<code bash>tail -f /soubor | stdbuf -o0 grep hledaneslovo</code>

===== ssh key pro vzdalene prihlasovani klientu pres ssh =====
ssh rsa key generovani - nezadavat passphrase
<code bash>ssh-keygen -t rsa</code>
prekopirovani na server
<code bash>ssh-copy-id user@ip_srv</code>

===== ssh klice 2 =====
**server**: jako root
<code bash>ssh-keygen -t rsa</code>
heslo nechame prazdne
<code bash>scp /root/.ssh/id_rsa.pub uzivatel@nacilovemstroji:/var/tmp/id_rsa.pub.temp</code>

**cilovy stroj**
<code bash>mkdir /root/.ssh
touch /root/.ssh/authorized_keys
chmod 700 ~/.ssh
chmod 600 ~/.ssh/authorized_keys
cat /var/tmp/id_rsa.pub.temp >> ~/.ssh/authorized_keys</code>

===== symlink zmena targetu bez smazani =====
<code bash>ln -f -s /home/zdroj /home/symlink</code>

===== SED =====
<code bash>sed -i 's/original/new/g' file.txt</code>
-i = in-place (i.e. save back to the original file)
s = the substitute command
g = global (i.e. replace all and not just the first occurrence)

===== awk =====
<code bash>vstup | awk -F'[^0-9]*' '/real/{print $3"."$4}'</code>
najde numericke hodnoty za "real", treti a ctvrta pozice a prida tecku

===== OPENSSL na Debianu =====

<code bash>apt install certbot python-certbot-apache</code>

zkontrolovat /etc/hosts, jestli je cele jmeno na lokalni IP a generujeme:

<code bash>certbot --authenticator standalone --installer apache</code>

Pak to chce zkusit na automatickou obnovu udelat skript a dat do cronu pomoci

<code bash>certbot renew</code>


===== Rdiff-backup =====
**backup - server** a nasledne i klient jako root

<code bash>apt-get install rdiff-backup
rdiff-backup --version</code>

  * verze server - klient by se mely shodovat
  * vygenerujeme klice pro roota, dle ssh klic 2 a budeme distribuovat na klienty nasledne

<code bash>mkdir -p /var/backups/jmenoslozkyzalohy</code>

**priklad zalohy**

<code bash>rdiff-backup --exclude /tmp --exclude /mnt --exclude /proc --exclude /sys --exclude /run --exclude /dev --exclude /var/backup -v5 root@10.133.1.32::/ /var/backups/32/</code>

takhle s tim do cronu
<file bash gpiobackup.sh>
!/bin/bash
## gpiobackup script
# Backup
rdiff-backup --exclude /tmp --exclude /mnt --exclude /proc --exclude /sys --exclude /run --exclude /dev --exclude /var/backup -v5 root@10.133.$
sleep 5
rdiff-backup --exclude /tmp --exclude /mnt --exclude /proc --exclude /sys --exclude /run --exclude /dev --exclude /var/backup -v5 root@10.133.$
sleep 5
rdiff-backup --exclude /tmp --exclude /mnt --exclude /proc --exclude /sys --exclude /run --exclude /dev --exclude /var/backup -v5 root@10.133.$
# Clean Increments
rdiff-backup --force --remove-older-than 4B /var/backups/32
rdiff-backup --force --remove-older-than 4B /var/backups/33
rdiff-backup --force --remove-older-than 4B /var/backups/34
</file>===== tail =====
vypis logu v realnem case
<code bash>tail -f /soubor</code>
vyber ze souboru
<code bash>tail -f /soubor | grep --line-buffered hledaneslovo</code>
<code bash>tail -f /soubor | stdbuf -o0 grep hledaneslovo</code>