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+.. _command-scripting:
+
+Command Scripting
+=================
+
+VyOS supports executing configuration and operational commands non-interactively
+from shell scripts.
+
+To include VyOS specific functions and aliases you need to ``source
+/opt/vyatta/etc/functions/script-template`` files at the top of your script.
+
+.. code-block:: none
+
+  #!/bin/vbash
+  source /opt/vyatta/etc/functions/script-template
+  exit
+
+Run configuration commands
+--------------------------
+
+Configuration commands are executed just like from a normal config session. For
+example, if you want to disable a BGP peer on VRRP transition to backup:
+
+.. code-block:: none
+
+  #!/bin/vbash
+  source /opt/vyatta/etc/functions/script-template
+  configure
+  set protocols bgp 65536 neighbor 192.168.2.1 shutdown
+  commit
+  exit
+
+Run operational commands
+------------------------
+
+Unlike a normal configuration sessions, all operational commands must be
+prepended with ``run``, even if you haven't created a session with configure.
+
+.. code-block:: none
+
+  #!/bin/vbash
+  source /opt/vyatta/etc/functions/script-template
+  run show interfaces
+  exit
+
+Other script language
+---------------------
+
+If you want to script the configs in a language other than bash you can have
+your script output commands and then source them in a bash script.
+
+Here is a simple example:
+
+.. code-block:: python
+
+  #!/usr/bin/env python
+  print "delete firewall group address-group somehosts"
+  print "set firewall group address-group somehosts address '192.0.2.3'"
+  print "set firewall group address-group somehosts address '203.0.113.55'"
+
+
+.. code-block:: none
+
+  #!/bin/vbash
+  source /opt/vyatta/etc/functions/script-template
+  configure
+  source < /config/scripts/setfirewallgroup.py
+  commit
+
+
+Executing Configuration Scripts
+-------------------------------
+
+There is a pitfall when working with configuration scripts. It is tempting to
+call configuration scripts with "sudo" (i.e., temporary root permissions),
+because that's the common way on most Linux platforms to call system commands.
+
+On VyOS this will cause the following problem: After modifying the configuration
+via script like this once, it is not possible to manually modify the config
+anymore:
+
+.. code-block:: none
+
+  sudo ./myscript.sh # Modifies config
+  configure
+  set ... # Any configuration parameter
+
+This will result in the following error message: ``Set failed`` If this happens,
+a reboot is required to be able to edit the config manually again.
+
+To avoid these problems, the proper way is to call a script with the
+``vyattacfg`` group, e.g., by using the ``sg`` (switch group) command:
+
+.. code-block:: none
+
+  sg vyattacfg -c ./myscript.sh
+
+To make sure that a script is not accidentally called without the ``vyattacfg``
+group, the script can be safeguarded like this:
+
+.. code-block:: none
+
+  if [ "$(id -g -n)" != 'vyattacfg' ] ; then
+      exec sg vyattacfg -c "/bin/vbash $(readlink -f $0) $@"
+  fi
+
+Postconfig on boot
+------------------
+
+The ``/config/scripts/vyos-postconfig-bootup.script`` script is called on boot
+after the VyOS configuration is fully applied.
+
+Any modifications done to work around unfixed bugs and implement enhancements
+which are not complete in the VyOS system can be placed here.
+
+The default file looks like this:
+
+.. code-block:: none
+
+  #!/bin/sh
+  # This script is executed at boot time after VyOS configuration is fully
+  # applied. Any modifications required to work around unfixed bugs or use
+  # services not available through the VyOS CLI system can be placed here.
+
+.. hint:: For configuration/upgrade management issues, modification of this
+   script should be the last option. Always try to find solutions based on CLI
+   commands first.