balenad error on read-only filesystem

[ben-auo]

I have a system where only the /perm directory is mounted read-write. How can I run balena-engine in that situation?

# ls -al /etc/balena-engine/
total 0
dr-xr-xr-x    1 0        0                3 Jul 14 23:23 .
dr-xr-xr-x    6 0        0              270 Jul 14 23:23 ..
# balenad --data-root /perm/data --exec-root /perm/root --config-file /perm/daemon.json
...
INFO[2025-07-14T23:25:37.716481110-07:00] loading plugin "io.containerd.grpc.v1.version"...  type=io.containerd.grpc.v1
INFO[2025-07-14T23:25:37.716496645-07:00] loading plugin "io.containerd.tracing.processor.v1.otlp"...  type=io.containerd.tracing.processor.v1
INFO[2025-07-14T23:25:37.716525452-07:00] skip loading plugin "io.containerd.tracing.processor.v1.otlp"...  error="no OpenTelemetry endpoint: skip plugin" type=io.containerd.tracing.processor.v1
INFO[2025-07-14T23:25:37.716536839-07:00] loading plugin "io.containerd.internal.v1.tracing"...  type=io.containerd.internal.v1
ERRO[2025-07-14T23:25:37.716562069-07:00] failed to initialize a tracing processor "otlp"  error="no OpenTelemetry endpoint: skip plugin"
INFO[2025-07-14T23:25:37.716615736-07:00] loading plugin "io.containerd.ttrpc.v1.task"...  type=io.containerd.ttrpc.v1
WARN[2025-07-14T23:25:37.716637381-07:00] failed to load plugin io.containerd.ttrpc.v1.task  error="no io.containerd.event.v1 plugins with id publisher: not found"
INFO[2025-07-14T23:25:37.716819027-07:00] serving...                                    address=/perm/root/containerd/balena-engine-containerd-debug.sock
INFO[2025-07-14T23:25:37.716874176-07:00] serving...                                    address=/perm/root/containerd/balena-engine-containerd.sock.ttrpc
INFO[2025-07-14T23:25:37.716910904-07:00] serving...                                    address=/perm/root/containerd/balena-engine-containerd.sock
INFO[2025-07-14T23:25:37.716925101-07:00] containerd successfully booted in 0.014823s  
INFO[2025-07-14T23:25:37.751446100-07:00] [graphdriver] using prior storage driver: overlay2 
INFO[2025-07-14T23:25:37.755675358-07:00] stopping healthcheck following graceful shutdown  module=libcontainerd
INFO[2025-07-14T23:25:37.755789144-07:00] stopping event stream following graceful shutdown  error="context canceled" module=libcontainerd namespace=plugins.moby
failed to start daemon: Error saving key file: open /etc/balena-engine/.tmp-key.json3660459214: read-only file system