symlink prevents ephemeral disk migration

[mmickan]

Nomad version

Nomad v0.5.6

Operating system and Environment details

Linux docker-3 4.4.0-77-generic #98-Ubuntu SMP Wed Apr 26 08:34:02 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux

Issue

Ephemeral disks cannot be migrated successfully if they contain a symlink.

Reproduction steps

1. Start a job with an ephemeral disk, with migration, and create a symlink under /local:

job "test" {
  region = "vagrant"
  datacenters = ["vagrant"]
  type = "service"
  group "test" {
    ephemeral_disk {
      migrate = true
      sticky = true
    }
    task "test" {
      driver = "exec"
      config {
        command = "/local/test.sh"
      }
      template {
        data = <<EOH
#!/bin/bash
ls -l /local

touch /local/alpha
ln -s /local/alpha /local/beta
touch /local/gamma

tail -f /dev/null
EOH
        destination = "local/test.sh"
        perms = "555"
      }
    }
  }
}

2. Force the job to be moved to another host (e.g. using node-drain)

3. Review logs of new allocation, note that /local disk snapshot partially failed (should contain symlink beta and files alpha and gamma, but only contains file alpha):

total 4
-rw-r--r-- 1 nobody nogroup   0 Jun  3 20:11 alpha
-r-xr-xr-x 1 root   root    201 Jun  3 20:11 test.sh

Nomad Client logs (if appropriate)

[ERR] http: Request /v1/client/allocation/73c41715-7c0d-e28c-509e-84265bd0ff22/snapshot, error: error making snapshot: open /var/lib/nomad/alloc/73c41715-7c0d-e28c-509e-84265bd0ff22/test/local/beta: no such file or directory

[github-actions]

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