My Personal Cheat Sheet

A collection of commands, scripts and other snippets that I frequently or infrequently need.

This is my personal collection of notes, commands, and snippets that I often reach for (and sometimes forget). It’s a living document — a mix of quick references, gotchas, and practical examples across tools I use.

Ansible: Start at Task or Tag

Start at a specific task (by name):

ansible-playbook playbook.yml --start-at-task="example task"

Start at a specific task (by tag):

ansible-playbook playbook.yml --tags example_tag

Gentoo: Entering chroot

It is assumed that the root is already mounted in /mnt/chroot.

export MOUNTPOINT=/mnt/chroot

mount --types proc /proc "${MOUNTPOINT}/proc"
mount --rbind /sys "${MOUNTPOINT}/sys"
mount --make-rslave "${MOUNTPOINT}/sys"
mount --rbind /dev "${MOUNTPOINT}/dev"
mount --make-rslave "${MOUNTPOINT}/dev"
mount --bind /run "${MOUNTPOINT}/run"
mount --make-slave "${MOUNTPOINT}/run"

chroot "${MOUNTPOINT}"

Source: Gentoo AMD64 Handbook - Installing the Gentoo base system

Gentoo: Exiting chroot

The chroot can obviously be left by typing exit. This snippet does the cleanup afterwards.

It is assumed that the root is already mounted in /mnt/chroot. Remember to leave the mountpoint first.

export MOUNTPOINT=/mnt/chroot

umount -l "${MOUNTPOINT}/run"
umount -l "${MOUNTPOINT}/dev"
umount -l "${MOUNTPOINT}/sys"
umount -l "${MOUNTPOINT}/proc"

umount -R "${MOUNTPOINT}"

Source: Gentoo AMD64 Handbook - Configuring the bootloader

libvirt: 4K Resolution with QEMU QXL

To enable 4K resolution with QXL graphics the video memory needs to be increased. The following snippet can be used as an example.

<video>
    <model type='qxl' ram='262144' vram='524288' vgamem='65536' heads='1' primary='yes'/>
    <address type='pci' domain='0x0000' bus='0x00' slot='0x01' function='0x0'/>
</video>

macOS: Flush DNS Cache

When debugging DNS-related issues it may be useful to clear the DNS cache.

sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder

rsync: Trailing Slash Caveat

rsync follows the convention of BSD cp, which gives special treatment to source directories with a trailing slash /.

The following command creates a directory destination/source with the contents of source:

rsync -r source destination

The following command copies all files in source/ directly into destination.

rsync -r source/ destination

Source: Arch Linux Wiki - Rsync