Using the screen command

The screen command is available to execute long-running commands (for example, when upgrading) in the background.

The following commands require the running of screen:

  • cluster provision
  • cluster upgrade
  • app upgrade
  • app template
  • voss export type <args>
  • voss export group <args>
  • voss subscriber_data_export

A message is displayed to indicate that screen should be run first:

This is a potentially long-running command and should be executed in a screen session
Run `screen` and then execute the command again

The use of screen is not affected by the use of the --force parameter with any of these commands.

The commands then run in a screen session that can be reconnected. The standard screen command parameters are available, in particular:

  • screen - start a new session
  • screen -ls - show sessions already available
  • screen -r [screen PID] - reconnect to a disconnected session

The version of screen used in VOSS-4-UC also supports the creation of a log file. If long-running commands will be run, the log file captures screen console output up to the session timeout. A message shows:

timed out waiting for input: auto-logout

To create a screen log file:

  1. Run screen and wait for screen to open.
  2. Press <Ctrl>-a then : (colon). This will enter screen command mode at the bottom of the console.
  3. Create your screen logfile in the media/ directory:
    1. In screen command mode, type logfile media/<screen-logfilename>.log
    2. Press <Enter>
    3. Press <Ctrl>-a and then H to start writing to the log file
    4. Run your commands.

If the screen session times out, you can obtain console output from the log file, for example:

$ sftp platform@<host>:media/<screen-logfilename>.log