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qemu_template: add -S flag for snapshot mode #4310

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Merged
t-lo merged 1 commit into from
Oct 8, 2026
Merged

qemu_template: add -S flag for snapshot mode #4310

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15 changes: 11 additions & 4 deletions build_library/qemu_template.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@ SAFE_ARGS=0
FORWARDED_PORTS=""
PRIMARY_DISK_OPTS=""
DISKS=()
SNAPSHOT="off"
USAGE="Usage: $0 [-a authorized_keys] [--] [qemu options...]
Options:
-i FILE File containing an Ignition config
Expand Down Expand Up @@ -49,6 +50,9 @@ Options:
-K FILE Set kernel for direct boot used to simulate a PXE boot (with -r).
-r FILE Set initrd for direct boot used to simulate a PXE boot (with -K).
-s Safe settings: single simple cpu and no KVM.
-S Use snapshot mode for all drives / pflash devices.
Snapshot mode will never write modifications to disk.
All changes will be discarded when the VM shuts down.
-h this ;-)

This script is a wrapper around qemu for starting Flatcar virtual machines.
Expand Down Expand Up @@ -128,6 +132,9 @@ while [ $# -ge 1 ]; do
-r|-initrd-file)
VM_INITRD="$2"
shift 2 ;;
-S|-snapshot)
SNAPSHOT="on"
shift ;;
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-v|-verbose)
set -x
shift ;;
Expand Down Expand Up @@ -269,14 +276,14 @@ if [ -n "${CONFIG_DRIVE}" ]; then
fi

if [ -n "${CONFIG_IMAGE}" ]; then
set -- -drive if=virtio,file="${CONFIG_IMAGE}" "$@"
set -- -drive if=virtio,file="${CONFIG_IMAGE}",snapshot="${SNAPSHOT}" "$@"
fi

if [ -n "${VM_IMAGE}" ]; then
if [[ ,${PRIMARY_DISK_OPTS}, = *,drive=* || ,${PRIMARY_DISK_OPTS}, = *,bootindex=* ]]; then
die "Can't override drive or bootindex options for primary disk"
fi
set -- -drive if=none,id=blk,file="${VM_IMAGE}" \
set -- -drive if=none,id=blk,file="${VM_IMAGE}",snapshot="${SNAPSHOT}" \
-device virtio-blk-pci,drive=blk,bootindex=1${PRIMARY_DISK_OPTS:+,}${PRIMARY_DISK_OPTS:-} "$@"
fi

Expand All @@ -292,7 +299,7 @@ for disk in "${DISKS[@]}"; do
disk_opts=
fi
set -- \
-drive "if=none,id=${disk_id},file=${disk_path}" \
-drive "if=none,id=${disk_id},file=${disk_path},snapshot=${SNAPSHOT}" \
-device "virtio-blk-pci,drive=${disk_id}${disk_opts:+,}${disk_opts:-}" \
"${@}"
done
Expand All @@ -317,7 +324,7 @@ fi
if [ -n "${VM_PFLASH_RO}" ] && [ -n "${VM_PFLASH_RW}" ]; then
set -- \
-drive if=pflash,unit=0,file="${VM_PFLASH_RO}",format=qcow2,readonly=on \
-drive if=pflash,unit=1,file="${VM_PFLASH_RW}",format=qcow2 "$@"
-drive if=pflash,unit=1,file="${VM_PFLASH_RW}",format=qcow2,snapshot="${SNAPSHOT}" "$@"
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fi

if [ -n "${IGNITION_CONFIG_FILE}" ]; then
Expand Down
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