title: Haproxy external-check error code 255
body: <p>I'm quite new with Haproxy and I have a weird behavior with external check..</p>
  
  <p>here is my config file :</p>
  
  <pre><code>global
      log /dev/log    local0
      log /dev/log    local1 notice
      chroot /var/lib/haproxy
      stats socket /run/haproxy/admin.sock mode 660 level admin
      stats timeout 30s
      user haproxy
      group haproxy
      daemon
  
      # Default SSL material locations
      ca-base /etc/ssl/certs
      crt-base /etc/ssl/private
  
      # Default ciphers to use on SSL-enabled listening sockets.
      # For more information, see ciphers(1SSL). This list is from:
      #  https://hynek.me/articles/hardening-your-web-servers-ssl-ciphers/
      ssl-default-bind-ciphers ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:ECDH+3DES:DH+3DES:RSA+AESGCM:RSA+AES:RSA+3DES:!aNULL:!MD5:!DSS
      ssl-default-bind-options no-sslv3
      external-check
  
  defaults
      log    global
      mode    http
      option    httplog
      option    dontlognull
          timeout connect 5000
          timeout client  50000
          timeout server  50000
      errorfile 400 /etc/haproxy/errors/400.http
      errorfile 403 /etc/haproxy/errors/403.http
      errorfile 408 /etc/haproxy/errors/408.http
      errorfile 500 /etc/haproxy/errors/500.http
      errorfile 502 /etc/haproxy/errors/502.http
      errorfile 503 /etc/haproxy/errors/503.http
      errorfile 504 /etc/haproxy/errors/504.http
  
  backend web-backend
      balance roundrobin
      option external-check
      external-check path "/usr/bin:/bin:/tmp"
      external-check command /bin/true
      server web1 127.0.0.1:80 check
      server web2 127.0.0.1:81 check
  
  frontend http
      bind *:82
      mode http
  
      default_backend web-backend
  </code></pre>
  
  <p>And yet I get a 503 and in my logs I got this :</p>
  
  <pre><code>...: Server web-backend/web1 is DOWN, reason: External check error, code: 255, check duration: 5ms. 1 active and 0 backup servers left. 0 sessions active, 0 requeued, 0 remaining in queue.
  ...: Server web-backend/web1 is DOWN, reason: External check error, code: 255, check duration: 5ms. 1 active and 0 backup servers left. 0 sessions active, 0 requeued, 0 remaining in queue.
  ...: Server web-backend/web2 is DOWN, reason: External check error, code: 255, check duration: 1ms. 0 active and 0 backup servers left. 0 sessions active, 0 requeued, 0 remaining in queue.
  ...: Server web-backend/web2 is DOWN, reason: External check error, code: 255, check duration: 1ms. 0 active and 0 backup servers left. 0 sessions active, 0 requeued, 0 remaining in queue.
  ...: backend web-backend has no server available!
  ...: backend web-backend has no server available!
  </code></pre>
  
  <p>How could the check /bin/true fail and return 255 ?</p>
  
  <p>I'm running the latest stable version (1.6.5)</p>
  
  <p>Thanks !</p>
  
  <p><strong>EDIT</strong>
  I'm on Debian8 and I used this : <a href="https://haproxy.debian.net/" rel="nofollow">https://haproxy.debian.net/</a> to install the latest version (1.6.5)</p>