virtual-dsm/docs/environment.md

Environment Variables

This page lists all the environment variables that can be used to configure the container.

An empty default means the variable is unset and its value is determined automatically when applicable.

💽 Virtual DSM

Variable	Default	Description
URL		URL or local path to a custom .pat installation file.
COUNTRY		Country code used to select the Synology download mirror.
HOST_MAC		MAC address reported to DSM.
HOST_MODEL		Synology host model reported to DSM.
HOST_SERIAL		Synology host serial number reported to DSM.
GUEST_SERIAL		Synology guest serial number reported to DSM.

🧠 CPU and Memory

Variable	Default	Description
CPU_CORES	2	Number of virtual CPU cores, such as 4, half, or max.
CPU_MODEL	host	QEMU CPU model.
CPU_FLAGS		Additional QEMU CPU flags.
HOST_CPU		CPU name reported to DSM. Selected automatically when unset.
KVM	Y	Enables KVM hardware acceleration.
RAM_SIZE	2G	Amount of RAM assigned to DSM, such as 2G, 4G, half, or max.
RAM_CHECK	Y	Checks whether enough host memory is available before starting DSM.

💾 Storage

Variable	Default	Description
DISK_SIZE	256G	Size of the main data disk.
DISK_FMT	raw	Disk image format: raw or qcow2.
DISK_TYPE	scsi	Disk device type, such as ide, scsi, or blk.
DISK_CACHE	none	Disk cache mode, such as none or writeback.
DISK_IO	native	Disk I/O mode, such as native, threads, or io_uring.
DISK_DISCARD	unmap	Discard/TRIM mode for the primary disk.
DISK_ROTATION	1	Rotation rate reported to the guest. Use 1 to identify the disk as an SSD.
DISK_FLAGS		Additional options used when creating qcow2 disks.
DISK_OPTIONS		Additional options appended to QEMU disk devices.
ALLOCATE	N	Preallocates space for the data disks.
STORAGE	/storage	Storage directory used for disks, settings, and downloads.

🌐 Networking

Variable	Default	Description
NETWORK		Network mode, such as nat, user, or N to disable networking.
DHCP	N	Enables macvtap networking so DSM receives a DHCP address.
HOST		Hostname assigned to the machine on the network.
IP		Overrides the automatically selected guest IPv4 address.
MAC		Guest network adapter MAC address.
ADAPTER	virtio-net-pci	QEMU network adapter model.
DEV	eth0	Container network interface used as the uplink.
MTU		MTU assigned to the guest network interface.
MASK	255.255.255.0	IPv4 netmask for guest network.
TAP	qemu	TAP or macvtap interface name.
BRIDGE	docker	Bridge name used for NAT networking.
HOST_PORTS		Ports excluded from guest forwarding.
USER_PORTS		Additional ports to forward to DSM when using user-mode networking.
DNSMASQ_OPTS		Additional options passed to dnsmasq.
DNSMASQ_DEBUG	N	Enables dnsmasq debug output.
DNSMASQ_DISABLE	N	Disables the internal dnsmasq resolver.
PASST_OPTS		Additional options passed to passt.
PASST_DEBUG	N	Enables passt debug output.

🖥️ Display

Variable	Default	Description
DISPLAY	none	Display backend, such as vnc, disabled, or none.
VGA	none	QEMU video adapter model.
GPU	N	Enables experimental GPU acceleration.
RENDERNODE	/dev/dri/renderD128	Render node used for GPU acceleration.

🎈 Memory Ballooning

Also see Dynamic memory allocation for usage instructions and important caveats.

Variable	Default	Description
BALLOONING	N	Enables dynamic memory ballooning.
BALLOONING_MIN_MEM	33%	Minimum amount of memory retained by the VM.
BALLOONING_RAM_THRESHOLD	80.0	Host RAM usage percentage at which ballooning begins adjusting memory.
BALLOONING_RAM_THRESHOLD_HARD	90.0	Host RAM usage percentage at which ballooning becomes more aggressive.
BALLOONING_PSI_PRESSURE	10.0	PSI memory pressure level at which ballooning becomes more aggressive.
BALLOONING_PSI_PRESSURE_MAX	50.0	PSI memory pressure level at which ballooning reaches its strongest response.
BALLOONING_HYSTERESIS	128M	Minimum memory change before the balloon target is updated.
BALLOONING_KP	0.5	Proportional gain used by the ballooning controller.
BALLOONING_KI	0.05	Integral gain used by the ballooning controller.
BALLOONING_INTERVAL	5	Polling interval in seconds.
BALLOONING_DEBUG	N	Enables debug output for the ballooning monitor.

🔌 Shutdown

Variable	Default	Description
SHUTDOWN	Y	Enables graceful shutdown.
TIMEOUT	105	Maximum time, in seconds, to wait before forcing DSM to stop.
API_TIMEOUT	90	Maximum time, in seconds, to wait for the shutdown API call.

🐞 Debugging

Variable	Default	Description
DEBUG	N	Enables verbose debug output.
TRACE	N	Enables shell command tracing.
HOST_DEBUG	N	Enables debug output for the DSM host helper.
MONITOR		QEMU monitor configuration.
QMP		QEMU Machine Protocol configuration.
ARGUMENTS		Additional raw arguments appended to the QEMU command line.