diff --git a/doc/source/sysadmin.rst b/doc/source/sysadmin.rst
index c81c85c153..04329d80b5 100644
--- a/doc/source/sysadmin.rst
+++ b/doc/source/sysadmin.rst
@@ -302,10 +302,13 @@ roll-back to a known good state; see
 
 However, we have limited backup space.  Each backup server has a
 script ``/usr/local/bin/prune-borg-backups`` which can be run to
-reclaim space.  This will keep the last 7 days of backups, then
-monthly backups for 1 year and yearly backups for each archive.  The
-backup servers will send a warning when backup volume usage is high,
-at which point this can be run manually.
+reclaim space.  This should be run in a ``screen`` instance as it can
+take a considerable time.  It will prompt when run; you can confirm
+the process with a ``noop`` run; confirming the prune will log the
+output to ``/opt/backups``. This will keep the last 7 days of backups,
+then monthly backups for 1 year and yearly backups for each archive.
+The backup servers will send a warning when backup volume usage is
+high, at which point this can be run manually.
 
 .. _force-merging-a-change:
 
diff --git a/playbooks/roles/borg-backup-server/files/prune-borg-backups.sh b/playbooks/roles/borg-backup-server/files/prune-borg-backups.sh
index 945c429961..0ed9142b5a 100644
--- a/playbooks/roles/borg-backup-server/files/prune-borg-backups.sh
+++ b/playbooks/roles/borg-backup-server/files/prune-borg-backups.sh
@@ -10,6 +10,10 @@ if [[ ${borg_op} == 'noop' ]]; then
     BORG_OP='--dry-run'
 elif [[ ${borg_op} == 'prune' ]]; then
     BORG_OP=''
+    LOG_FILE="/opt/backups/prune-$(date '+%Y-%m-%d-%H-%M-%S').log"
+    echo "*** Logging output to ${LOG_FILE}"
+    exec 1>${LOG_FILE}
+    exec 2>&1
 else
     echo "*** Invalid input"
     exit 1
@@ -31,7 +35,7 @@ for u in borg-*; do
       echo
       echo
       echo "+------"
-      echo "| Pruning ${BORG_REPO} archive ${prefix}"
+      echo "| $(date) Pruning ${BORG_REPO} archive ${prefix}"
       echo "+------"
      /opt/borg/bin/borg prune --prefix ${prefix} ${BORG_OP} --verbose --list --show-rc --keep-daily 7 --keep-weekly 4 --keep-monthly 12
     done