When launching a new slave in EC2, it seems like everything works until it tries to run the init scripts. This fails like so: -

Connecting to ec2-*.compute-1.amazonaws.com on port 22.
Waiting for SSH to come up. Sleeping 5.
Connecting to ec2-*.compute-1.amazonaws.com on port 22.
Waiting for SSH to come up. Sleeping 5.
Connecting to ec2-*.compute-1.amazonaws.com on port 22.
Waiting for SSH to come up. Sleeping 5.
Connecting to ec2-*.compute-1.amazonaws.com on port 22.
Waiting for SSH to come up. Sleeping 5.
Connecting to ec2-*.compute-1.amazonaws.com on port 22.
Connected via SSH.
Authenticating as test
Executing init script
ERROR: Error during SCP transfer.
java.io.IOException: Error during SCP transfer.
at com.trilead.ssh2.SCPClient.put(SCPClient.java:523)
at hudson.plugins.ec2.ssh.EC2UnixLauncher.launch(EC2UnixLauncher.java:99)
at hudson.plugins.ec2.EC2ComputerLauncher.launch(EC2ComputerLauncher.java:80)
at hudson.slaves.SlaveComputer$1.call(SlaveComputer.java:230)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)
at java.lang.Thread.run(Thread.java:662)
Caused by: java.io.IOException: Remote scp terminated with error (scp: /tmp: No such file or directory).
at com.trilead.ssh2.SCPClient.readResponse(SCPClient.java:59)
at com.trilead.ssh2.SCPClient.sendBytes(SCPClient.java:140)
at com.trilead.ssh2.SCPClient.put(SCPClient.java:519)
... 8 more

I was able to manually log into the instance and verify that /tmp does exist, and I can write to it as the user that Jenkins authenticates with. /tmp, however, is a symlink to another directory.

I was also able to manually scp a file to /tmp like so: -

scp -i <jenkins ec2 key> README.md test@<ip>:/tmp

Is this a known issue? Anything more detail I can provide?