QEMU Commands: Notes for self

qemu-commands.md

QEMU Commands

References

• Youtube
• ArchWiki

Creating Image

qemu-img create -f qcow2 Image.img 10G Note: cow stands for copy-on-write

Resizing Image

For adding space to the image qemu-img resize disk_image +10G

For removing space qemu-img resize --shrink disk_image -10G

Running the VM

qemu-system-x86_64 -enable-kvm -cdrom OS_ISO.iso -boot menu=on -drive file=Image.img -m 4G

Note:

• change 4G to appropriate RAM allocation for the system
• remove the cdrom flag after installing the OS
• use -smp <CORE_NUM> to specified CPU cores
• add -vga virtio -display sdl,gl=on for performance
• add -device ich9-intel-hda -device hda-output for audio support (intel audio specific)

Other stuffs

• qemu-img info for information on the image
• -boot d flag to force boot the cdrom/iso
• -cpu host,+popcnt is needed on RHEL and SUSE, see: https://forums.virtualbox.org/viewtopic.php?f=3&t=106666

for UEFI copy over /usr/share/edk2/x64/OVMF_VARS.4m.fd to be readable and then do the follow (source: archwiki in ref):

-drive if=pflash,format=raw,readonly=on,file=/usr/share/edk2/x64/OVMF_CODE.4m.fd \
-drive if=pflash,format=raw,file=/copy/of/OVMF_VARS.4m.fd

Keybinds

CTRL+ALT+F fullscreen CTRL+ALT+Q quit CTRL+ALT+G to unfocus from the VM

Linux stuffs

After resizing (growing) an image, you can do the following to grow the partition:

1. cfdisk /dev/<drive> and then resize the partition there
2. e2fsck -f /dev/<partition> to check the partition
3. resize2fs /dev/<partition> to then grow the filesystem to the partition

For btrfs you can also just create a new partition with cfdisk and then use the command below sudo btrfs device add /dev/<partition> <mountpoint>

Example: sudo btrfs device add /dev/vda3 / would add the vda3 partition to be used for the / mountpoint. This seems to work better for atomic distros / if you're lazy to chroot and do all the resizing there.

#/usr/bin/sh
qemu-system-x86_64 -enable-kvm -boot menu=on -drive if=pflash,format=raw,readonly=on,file=/usr/share/edk2/x64/OVMF_CODE.4m.fd -drive if=pflash,format=raw,file=OVMF_VARS.4m.4d -drive file=PopOS.img -m 4G -smp 3 -vga virtio -device ich9-intel-hda -device hda-output

Example script for running PopOS (after it has been installed into the img) in QEMU with UEFI.

regarding btrfs, there's also btrfs-replace, which might be cleaner to use but is going to take some time to finish migrating things and such.