If you encounter an error like following when you run devel.sh of kestrel, it’s due to directory permission as the error message says.

tsakuma@~/kestrel/dist/kestrel$ sh ./scripts/devel.sh 
Starting kestrel in development mode…
net.lag.kestrel.InaccessibleQueuePath: Inaccessible queue path: Must be a directory and writable
 at net.lag.kestrel.QueueCollection.<init>(QueueCollection.scala:50)
 at net.lag.kestrel.Kestrel.start(Kestrel.scala:144)
 at net.lag.kestrel.Kestrel$.main(Kestrel.scala:311)
 at net.lag.kestrel.Kestrel.main(Kestrel.scala)

Kestrel requires two writable directories for spool and log. They can be configured in dist/kestrel/config/development.scala.

queuePath = "/var/spool/kestrel"
....
loggers = new LoggerConfig {
  level = Level.INFO
  handlers = new FileHandlerConfig {
    filename = "/var/log/kestrel.log"
    roll = Policy.Never

You need to change queuePath and filename above like /tmp/spool/kestrel and /tmp/log/kestrel.log.