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# OPS Cheat sheet

Create temporary swapfile

SIZE=1G
SWAPFILE=/tmp/swapfile
# Allocate the swap for $SIZE
sudo fallocate -l $SIZE $SWAPFILE
# Create swap
sudo mkswap $SWAPFILE
# Change rights for r/w for user only
sudo chmod 0600 $SWAPFILE
# Enable swap
sudo swapon $SWAPFILE
# Disable swap
sudo swapoff $SWAPFILE

Resize linux partition

  1. Install e2fsprogs
  2. Check your disk with fdisk -l
  3. Check your file system with e2fsck -f /dev/{disk}
  4. Resize your disk partition with resize2fs /dev/{disk}

## Crypto Disk

After formatting your disk with gnome-disks for example and installing cryptmount and cryptsetup.

  1. Create your crypt device mapper. Open the file /etc/crypttab and add a line for your device.
# <target name>	<source device>		<key file>	<options>
# This will name your crypt partition, which is located in /dev/sda4, home.
home	/dev/sda4	none	luks,retry=1
  1. Now you can update your fstab with the newly named file system /dev/mapper/home.
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
/dev/mapper/home	/home	ext4 defaults 0 2
  1. Restart your computer

Add user to a group

This is used for sudo and docker groups

usermod -aG $group $user

Booting from grub>

Just in case grub shows you the console instead of execute the kernel. Here is how to fix it.

# Invokes the pager, for paging long command outputs:
grub> set pager=1
# List all your hard drives and partitions and find your partition containing your /boot.
grub> ls
(hd0) (hd0,gpt2) (hd0,gpt1)
grub> ls (hd0,gpt1)/
boot/ ...

Now the part for executing a specified kernel.

grub> set root=(hd0,gpt1)
# You should match the id of your partition with the name e.g gpt1 => sda1
grub> linux /boot/vmlinuz-6.1.0-9-amd64 root=/dev/sda1
# Take the same version for vmlinux and initrd !
grub> initrd /boot/initrd.img-6.1.0-9-amd64
grub> boot

Your OS should boot now but it's not finished! You must write all your changes to your boot sector of your hard drive.

# update-grub
Generating grub configuration file ...
# grub-install /dev/sda
Installing for ...
Installation finished. No error reported