archive_command not being executed

I have a standby db server (SB1) that will soon become the master. SB1 is set up with streaming replication from the current master. I'm trying to set up a third server (SB2) as a slave/standby to SB1, so that when SB1 becomes the master, there will be a standby for it. First step is to get WAL files shipped from SB1->SB2.

Problem is I can't get the archive_command of SB1 to execute. The same archive_command on our current master calls into a script that scp's the WAL files to SB1. This works. I've also confirmed the script works from SB1->SB2 when run from the command line, as the postgres user, w/o a password request.

Furthermore, on SB1 I replaced the call to the script with a touch command, to see if archive_command was getting called at all:

# This script does the scp of the WAL file to the designated server/directory
#archive_command = '/opt/printra/sbin/handle_wal_files.sh %p db-backup /backup/WAL_ARCHIVE/auto'
archive_command = 'touch /var/lib/pgsql/testtouch'

and the testtouch file did not appear.

Here are some relevant settings from SB1:

postgres=# select * from pg_settings where name like 'archive%';

-[ RECORD 1 ]------------------------------------------------------------------------------------------

name | archive_command

setting | touch /var/lib/pgsql/testtouch

unit |

category | Write-Ahead Log / Archiving

short_desc | Sets the shell command that will be called to archive a WAL file.

extra_desc |

context | sighup

vartype | string

source | configuration file

min_val |

max_val |

enumvals |

boot_val |

reset_val | touch /var/lib/pgsql/testtouch

sourcefile | /var/lib/pgsql/9.3/data/postgresql.conf

sourceline | 607

-[ RECORD 2 ]------------------------------------------------------------------------------------------

name | archive_mode

setting | on

unit |

category | Write-Ahead Log / Archiving

short_desc | Allows archiving of WAL files using archive_command.

extra_desc |

context | postmaster

vartype | bool

source | configuration file

min_val |

max_val |

enumvals |

boot_val | off

reset_val | on

sourcefile | /var/lib/pgsql/9.3/data/postgresql.conf

sourceline | 604

-[ RECORD 3 ]------------------------------------------------------------------------------------------

name | archive_timeout

setting | 0

unit | s

category | Write-Ahead Log / Archiving

short_desc | Forces a switch to the next xlog file if a new file has not been started within N seconds.

extra_desc |

context | sighup

vartype | integer

source | default

min_val | 0

max_val | 1073741823

enumvals |

boot_val | 0

reset_val | 0

sourcefile |

sourceline |

postgres=# select version();

-[ RECORD 1 ]-----------------------------------------------------------------------------------------------------------

version | PostgreSQL 9.3.19 on x86_64-unknown-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-11), 64-bit

I've bumped up logging to debug1 and have not seen anything that looks related to the archive_command. Bumping up to debug2 was really noisy and didn't seem to yield any useful info either. Any ideas?