diff --git a/src/openec2/actions/deregister_image.py b/src/openec2/actions/deregister_image.py
new file mode 100644
index 0000000..8bebcf7
--- /dev/null
+++ b/src/openec2/actions/deregister_image.py
@@ -0,0 +1,26 @@
+from fastapi import HTTPException
+from fastapi.datastructures import QueryParams
+from sqlmodel import select
+
+from openec2.config import OpenEC2Config
+from openec2.db import DatabaseDep
+from openec2.db.image import AMI
+from openec2.images import garbage_collect_image
+
+def deregister_image(
+    params: QueryParams,
+    config: OpenEC2Config,
+    db: DatabaseDep,
+):
+    image_id = params["ImageId"]
+    ami = db.exec(select(AMI).where(AMI.id == image_id)).one()
+    if ami is None:
+        raise HTTPException(status_code=404, detail="Unknown AMI")
+
+    # Mark the image as deregistered
+    ami.deregistered = True
+    db.add(ami)
+    db.commit()
+
+    # First round of garbage collection
+    garbage_collect_image(image_id, db)
diff --git a/src/openec2/actions/run_instances.py b/src/openec2/actions/run_instances.py
index 6f2f531..27657a5 100644
--- a/src/openec2/actions/run_instances.py
+++ b/src/openec2/actions/run_instances.py
@@ -4,23 +4,28 @@ from typing import cast
 import uuid
 import os
 
+from fastapi import HTTPException
 from fastapi.datastructures import QueryParams
 from sqlmodel import select
 
 from openec2.libvirt import LibvirtSingleton
 from openec2.config import OpenEC2Config
+from openec2.utils.qemu import create_cow_copy
 from openec2.db import DatabaseDep
 from openec2.db.instance import Instance
 from openec2.db.image import AMI
 from openec2.api.run_instances import RunInstanceResponse, RunInstanceInstanceSet
 from openec2.api.describe_instances import describe_instance
 from openec2.utils.array import parse_array_objects
+from openec2.ipam import get_available_ipv4, is_ipv4_available, add_instance_dhcp_mapping
+from openec2.utils.ip import generate_available_mac
 
 def create_libvirt_domain(
     name: str,
     memory: int,
     vcpu: int,
     ami_path: str,
+    mac: str,
     user_data: str | None,
 ) -> str:
     return f"""
@@ -70,7 +75,7 @@ def create_libvirt_domain(
         </rng>
         <interface type="network">
             <source network="default"/>
-            <mac address="52:54:00:58:81:8f"/>
+            <mac address="{mac}"/>
             <model type="virtio"/>
         </interface>
     </devices>
@@ -93,31 +98,51 @@ def run_instances(
     if ami is None:
         raise Exception(f"Unknown AMI {image_id}")
 
+    if ami.deregistered:
+        raise HTTPException(
+            status_code=400,
+            detail="AMI is deregistered and cannot be used anymore",
+        )
+
     # Parse tags
+    # TODO: broken
     tags: dict[str, str] = {}
     for spec in parse_array_objects("TagSpecification", cast(dict, params)):
         for raw_tag in parse_array_objects("Tag", spec):
             tags[raw_tag["Key"]] = raw_tag["Value"]
 
-    # Prepare the instance directory
+    # Get a private IPv4
     instance_id = uuid.uuid4().hex
+    private_ipv4 = params.get(
+        "PrivateIpAddress",
+        get_available_ipv4(db),
+    )
+    if not is_ipv4_available(private_ipv4, db):
+        raise HTTPException(
+            status_code=400,
+            detail="Used IPv4",
+        )
+    mac = generate_available_mac(db)
+    add_instance_dhcp_mapping(instance_id, mac, private_ipv4, db)
+
+    # Prepare the instance directory
     config.instances.location.mkdir(exist_ok=True)
     disk = config.instances.location / instance_id
-    shutil.copy(
-        str(config.images / ami.id),
-        str(disk),
+    create_cow_copy(
+        config.images / ami.id,
+        disk,
+        f"{instance_type.disk}G",
     )
-    os.system(f"qemu-img resize {disk} {instance_type.disk}G")
 
     instance = Instance(
         id=instance_id,
         imageId=image_id,
         tags=tags,
         userData=base64.b64decode(value).decode() if (value := params.get("UserData")) is not None else None,
+        privateIPv4=private_ipv4,
+        interfaceMac=mac,
     )
     db.add(instance)
-    db.flush()
-    db.commit()
     print("Inserted new instance")
 
     conn = LibvirtSingleton.of().connection
@@ -127,12 +152,14 @@ def run_instances(
             instance_type.memory,
             int(instance_type.vcpu),
             str(config.instances.location / instance_id),
+            mac,
             None,
         ),
     )
     domain.create()
     description = describe_instance(instance, domain)
 
+    db.commit()
     return RunInstanceResponse(
         request_id=uuid.uuid4().hex,
         instance_set=RunInstanceInstanceSet(
diff --git a/src/openec2/actions/terminate_instances.py b/src/openec2/actions/terminate_instances.py
index 4eb15c5..5b07371 100644
--- a/src/openec2/actions/terminate_instances.py
+++ b/src/openec2/actions/terminate_instances.py
@@ -9,6 +9,8 @@ from openec2.config import OpenEC2Config
 from openec2.db import DatabaseDep
 from openec2.db.instance import Instance
 from openec2.utils.array import parse_array_plain
+from openec2.images import garbage_collect_image
+from openec2.ipam import remove_instance_dhcp_mapping
 
 
 logger = logging.getLogger()
@@ -19,6 +21,7 @@ def terminate_instances(
     db: DatabaseDep,
 ):
     conn = LibvirtSingleton.of().connection
+    image_ids: set[str] = set()
     for instance_id in parse_array_plain("InstanceId", params):
         instance = db.exec(select(Instance).where(Instance.id == instance_id)).first()
         if instance is None:
@@ -34,7 +37,14 @@ def terminate_instances(
         instance_disk = config.instances.location / instance_id
         instance_disk.unlink()
 
+        image_ids.add(instance.imageId)
+        remove_instance_dhcp_mapping(instance.id, instance.interfaceMac, instance.privateIPv4, db)
         db.delete(instance)
-        db.commit()
+
+    db.commit()
+
+    # Garbage collect AMIs
+    for image_id in image_ids:
+        garbage_collect_image(image_id, db)
 
     return "OK"
diff --git a/src/openec2/db/image.py b/src/openec2/db/image.py
index 4b05004..60be1fc 100644
--- a/src/openec2/db/image.py
+++ b/src/openec2/db/image.py
@@ -1,8 +1,14 @@
 from sqlmodel import SQLModel, Field
 
 class AMI(SQLModel, table=True):
+    # ID of the AMI
     id: str = Field(default=None, primary_key=True)
 
+    # Description of the image
     description: str | None = None
 
+    # Filename that got imported
     originalFilename: str
+
+    # Was the image registered
+    deregistered: bool = Field(default=False)
diff --git a/src/openec2/db/instance.py b/src/openec2/db/instance.py
index 3d440e2..a6428e6 100644
--- a/src/openec2/db/instance.py
+++ b/src/openec2/db/instance.py
@@ -11,3 +11,9 @@ class Instance(SQLModel, table=True):
 
     # Optional user data associated with the VM
     userData: str | None
+
+    # MAC of the network interface
+    interfaceMac: str
+
+    # Private IPv4 of the instance
+    privateIPv4: str
diff --git a/src/openec2/db/ipam.py b/src/openec2/db/ipam.py
new file mode 100644
index 0000000..b528291
--- /dev/null
+++ b/src/openec2/db/ipam.py
@@ -0,0 +1,24 @@
+from sqlmodel import SQLModel, Field, PrimaryKeyConstraint
+
+from openec2.utils.ip import int_to_ipv4, ipv4_to_int
+
+
+class IPAMEntry(SQLModel, table=True):
+    # IP Address
+    ipv4_addr_raw: int = Field(primary_key=True)
+
+    # Instance this IP is assigned to
+    instance_id: str = Field(primary_key=True)
+
+    # VPC ID
+    vpc_id: str
+
+    def ipv4(self) -> str:
+        return int_to_ipv4(self.ipv4_addr_raw)
+
+    def set_ipv4(self, addr: str):
+        self.ipv4_addr_raw = ipv4_to_int(addr)
+
+    __table_args = (
+        PrimaryKeyConstraint("ipv4_addr_raw", "vpc_id"),
+    )
diff --git a/src/openec2/db/vpc.py b/src/openec2/db/vpc.py
new file mode 100644
index 0000000..2253c9e
--- /dev/null
+++ b/src/openec2/db/vpc.py
@@ -0,0 +1,11 @@
+from sqlmodel import SQLModel, Field, PrimaryKeyConstraint
+
+class VPC(SQLModel, table=True):
+    # ID of the VPC
+    id: str = Field(default=None, primary_key=True)
+
+    # Subnet mask
+    subnet: str
+
+    # Base IPv4
+    ipv4_base: str
diff --git a/src/openec2/images.py b/src/openec2/images.py
new file mode 100644
index 0000000..6c804ee
--- /dev/null
+++ b/src/openec2/images.py
@@ -0,0 +1,22 @@
+from sqlmodel import select
+
+from openec2.config import ConfigSingleton
+from openec2.db import DatabaseDep
+from openec2.db.instance import Instance
+from openec2.db.image import AMI
+
+
+def garbage_collect_image(image_id: str, db: DatabaseDep):
+    instances = db.exec(select(Instance).where(Instance.imageId == image_id)).all()
+    if instances:
+        print("Instances sill using AMI. Not cleaning up")
+        print(instances)
+        return
+
+    ami = db.exec(select(AMI).where(AMI.id == image_id, AMI.deregistered == True)).first()
+    if ami is not None:
+        db.delete(ami)
+        db.commit()
+        image = ConfigSingleton.of().config.images / image_id
+        image.unlink()
+        print(f"Removing {image}")
diff --git a/src/openec2/ipam.py b/src/openec2/ipam.py
new file mode 100644
index 0000000..8cb6539
--- /dev/null
+++ b/src/openec2/ipam.py
@@ -0,0 +1,61 @@
+from sqlmodel import select
+import libvirt
+
+from openec2.libvirt import LibvirtSingleton
+from openec2.db import DatabaseDep
+from openec2.db.ipam import IPAMEntry
+from openec2.utils.ip import ipv4_to_int, int_to_ipv4
+
+
+def _libvirt_host_update(instance_id: str, mac: str, ipv4: str) -> str:
+    return f"<host name='{instance_id}' mac='{mac}' ip='{ipv4}' />"
+
+
+def add_instance_dhcp_mapping(instance_id: str, mac: str, ipv4: str, db: DatabaseDep):
+    """
+    Adds a DHCP entry for the network to give the instance a static
+    private IPv4 address.
+    """
+    entry = IPAMEntry(
+        ipv4_addr_raw=ipv4_to_int(ipv4),
+        instance_id=instance_id,
+        # TODO
+        vpc_id="default",
+    )
+    db.add(entry)
+
+    # Tell libvirt about this mapping
+    conn = LibvirtSingleton.of().connection
+    conn.networkLookupByName("default").update(
+        libvirt.VIR_NETWORK_UPDATE_COMMAND_ADD_LAST,
+        libvirt.VIR_NETWORK_SECTION_IP_DHCP_HOST,
+        0,
+        _libvirt_host_update(instance_id, mac, ipv4),
+        flags=libvirt.VIR_NETWORK_UPDATE_AFFECT_LIVE,
+    )
+
+def remove_instance_dhcp_mapping(instance_id: str, mac: str ,ipv4: str, db: DatabaseDep):
+    i = ipv4_to_int(ipv4)
+    entry = db.exec(select(IPAMEntry).where(IPAMEntry.ipv4_addr_raw == i, IPAMEntry.instance_id == instance_id)).first()
+    db.delete(entry)
+
+    # Tell libvirt about this mapping
+    conn = LibvirtSingleton.of().connection
+    conn.networkLookupByName("default").update(
+        libvirt.VIR_NETWORK_UPDATE_COMMAND_DELETE,
+        libvirt.VIR_NETWORK_SECTION_IP_DHCP_HOST,
+        0,
+        _libvirt_host_update(instance_id, mac, ipv4),
+        flags=libvirt.VIR_NETWORK_UPDATE_AFFECT_LIVE,
+    )
+
+def is_ipv4_available(ipv4: str, db: DatabaseDep) -> bool:
+    i = ipv4_to_int(ipv4)
+    return db.exec(select(IPAMEntry).where(IPAMEntry.ipv4_addr_raw == i)).first() is None
+
+def get_available_ipv4(db: DatabaseDep) -> str:
+    entries = db.exec(select(IPAMEntry)).all()
+    # TODO: Use the VPC's subnet
+    max_ip = max(e.ipv4_addr_raw for e in entries) if entries else ipv4_to_int("192.168.122.2")
+    # TODO: Check if we're still inside the subnet
+    return int_to_ipv4(max_ip + 1)
diff --git a/src/openec2/main.py b/src/openec2/main.py
index c6e30ef..40a50d1 100644
--- a/src/openec2/main.py
+++ b/src/openec2/main.py
@@ -12,6 +12,7 @@ from openec2.actions.run_instances import run_instances
 from openec2.actions.terminate_instances import terminate_instances
 from openec2.actions.start_instances import start_instances
 from openec2.actions.stop_instances import stop_instances
+from openec2.actions.deregister_image import deregister_image
 from openec2.db.instance import Instance
 
 app = FastAPI()
@@ -37,6 +38,7 @@ def action(request: Request, config: OpenEC2Config, db: DatabaseDep):
         "TerminateInstances": terminate_instances,
         "StartInstances": start_instances,
         "StopInstances": stop_instances,
+        "DeregisterImage": deregister_image,
     }[action](request.query_params, config, db)
 
 @app.get("/private/cloudinit/{instance_id}/{entry}")
diff --git a/src/openec2/utils/ip.py b/src/openec2/utils/ip.py
new file mode 100644
index 0000000..d12f0b3
--- /dev/null
+++ b/src/openec2/utils/ip.py
@@ -0,0 +1,44 @@
+import random
+
+from sqlmodel import select
+
+from openec2.db import DatabaseDep
+from openec2.db.instance import Instance
+
+
+def ipv4_to_int(ip: str) -> int:
+    i = 0
+    for idx, p in enumerate(ip.split(".")):
+        i += (int(p) << (3-idx)*8)
+    return i
+
+def int_to_ipv4(ip: int) -> str:
+    parts: list[int] = []
+    for i in reversed(range(4)):
+        parts.append(
+            (ip >> i*8) & 255,
+        )
+    return ".".join(str(p) for p in parts)
+
+def generate_mac() -> str:
+    mac_bytes = random.randbytes(6)
+    mac = ""
+    for idx, b in enumerate(mac_bytes):
+        # Ensure we have a unicast MAC
+        if idx == 0:
+            b = b & (255 - 1)
+
+        h = hex(b)[2:]
+        if len(h) == 1:
+            mac += f"0{h}:"
+        else:
+            mac += f"{h}:"
+    return mac[:-1]
+
+def generate_available_mac(db: DatabaseDep) -> str:
+    mac = ""
+    while True:
+        mac = generate_mac()
+        if db.exec(select(Instance).where(Instance.interfaceMac == mac)).first() is None:
+            break
+    return mac
diff --git a/src/openec2/utils/qemu.py b/src/openec2/utils/qemu.py
new file mode 100644
index 0000000..542a0e6
--- /dev/null
+++ b/src/openec2/utils/qemu.py
@@ -0,0 +1,14 @@
+from pathlib import Path
+import subprocess
+
+
+def create_cow_copy(src: Path, dst: Path, size: str):
+    subprocess.call([
+        "qemu-img",
+        "create",
+        "-f", "qcow2",
+        "-b", str(src),
+        "-F", "qcow2",
+        str(dst),
+        size,
+    ])
diff --git a/tests/openec2/test_ip.py b/tests/openec2/test_ip.py
new file mode 100644
index 0000000..54678c6
--- /dev/null
+++ b/tests/openec2/test_ip.py
@@ -0,0 +1,8 @@
+from openec2.utils.ip import ipv4_to_int, int_to_ipv4
+
+
+def test_idempotent():
+    ip = "127.0.0.1"
+    ip_int = ipv4_to_int(ip)
+    print(ip_int)
+    assert int_to_ipv4(ip_int) == ip