Linux

iptables

sudo iptables -t nat -A PREROUTING --dst 192.168.100.101 -p tcp --dport 1900 -j DNAT --to-destination 10.0.0.2:1880 server:1900 -> vm:1880

mail

MTA - передача писем, только SMTP
MDA - получение писем, MDA общается с MTA для их получения

MTA - exim, postfix, sendmail
MDA - dovecot, cyrus

nextcloud preview configuration

I don't want to generate all the preview sizes


This is possible since version 1.0.8. Just set the correct values via the command line 
``` ./occ config:app:set --value="32 64 1024" previewgenerator squareSizes ./occ config:app:set --value="64 128 1024" previewgenerator widthSizes ./occ config:app:set --value="64 256 1024" previewgenerator heightSizes ``` 
This will only generate:

• square previews ofL 32x32, 64x64 and 1024x1024* aspect ratio previews with a width of: 64, 128 and 1024
• aspect ratio previews with a height of: 64, 256 and 1024


Note:

• preview sizes are always a power of 2.
• The smallest size is 32
• The max size is determined by your preview settings in config.php

Some stuff

disown -a && exit - выйти не закрывая работающие процессы

VirtualBox

VBoxManage clonehd absolutepath/image.vdi image.img --format raw - сконвертировать vdi в сырой диск