Extraits de code SystM

des bouts de code bash et autre pour debian et autres linux based servers

• Configurations
• Swap file and swapiness for production servers
• ffmpeg
• ffmpeg : Transformer un son wav en mp3
• ffmpeg : transformer un mp4 en webm
• Automatisations
• Server hints
• mysql / mariadb : create db, user and grant oneliner
• fail2ban : list banned IPs and unban

Configurations

des réglages aux petits oignons

Swap file and swapiness for production servers

Swapfile

Howto create a 2Gb swapfile, enable it, and add to fstab

fallocate -l 2G /swapfile
chmod 600 /swapfile
mkswap /swapfile
swapon /swapfile
echo '/swapfile none swap sw 0 0' | sudo tee -a /etc/fstab

Swapiness

While the swappiness value of 60 is OK for most Linux systems, for production servers, you may need to set a lower value.

For example, to set the swappiness value to 10, run:

sysctl vm.swappiness=10

To make this parameter persistent across reboots, append the following line to the /etc/sysctl.conf file:

vm.swappiness=10

ffmpeg

ffmpeg : Transformer un son wav en mp3

cette commande permet de convertir un audio du format wav au format mp3 :

 ffmpeg -i son.wav -acodec mp3 -ab 128k son.mp3

merci qui? merci ffmpeg!

ffmpeg : transformer un mp4 en webm

la commande suivant converti une vidéo au format mp4 en webm avec les bons codecs audio / video :

ffmpeg -i video.mp4 -vf scale=1920:1080 -movflags faststart -f webm -c:v libvpx -b:v 3M -acodec libvorbis video.webm

merci qui, merci ffmpeg!

Automatisations

Server hints

mysql / mariadb : create db, user and grant oneliner

CREATE DATABASE dbname CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci; CREATE USER dbuser@localhost identified by 'pwd'; GRANT ALL PRIVILEGES on dbname.* to dbuser@localhost; FLUSH privileges;

Restore a Single MySQL Database from a Full MySQL Dump

If you backed up all your databases using the -all-databases option and you want to restore a single database from a backup file which contains multiple databases use the --one-database option as shown below:

mysql --one-database database_name < all_databases.sql

Export and Import a MySQL Database in One Command

Instead of creating a dump file from one database and then import the backup into another MySQL database you can use the following one-liner:

mysqldump -u root -p database_name | mysql -h remote_host -u root -p remote_database_name

The command above will pipe the output to a mysql client on the remote host and it will import it into a database named remote_database_name. Before running the command, make sure the database already exists on the remote server

fail2ban : list banned IPs and unban

to find all banned IPs for a specific jail, example sshd jail :

fail2ban-client status sshd

then unban the desired IP :

fail2ban-client set sshd unbanip xx.xx.xx.xx