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Start dockerd on a read only mounted disk - fails due missing key.json file


I try to start dockerd on a system with read only mounted disk, which results in this error

Error starting daemon: Error saving key file: open /etc/docker/.tmp-key.json066578129: read-only file system

There are a couple of options to define the location of daemon.json, tls certificate files etc. but no setting to define the location of the key.json.

The machine has rw mounted partitions - so what I need is to select another file path.

Is this possible?

Thanks and cheers

Have you tried mounting an overlay (into ramfs) ontop of /etc ?
That way the directory becomes writable - writes go into tmpfs, so any changes are lost on reboot.