Backup Script

Backup Script

Goals

You want to schedule a backup to be done via a cron job.
You want the script initiated from, and stored in a safe location
on a server on the network, (not on the router).
You do not wish to install SFTP just for these backups.

The script at the bottom of this page will create and download the backup without needing to have SFTP enabled on the router.

You could, of course, create the backup as a cron job on the router itself, and then use the mechanism applied in the script below to download the backup file. However, let's assume you want everything done in just one run of the script. To achieve this, the script covers creation of the backup in an individual file with timestamp and download.

In this way, just one run of the script on the backup server will create the backup and download it to to a safe location.

The backup is created using the “nvram save” command. This is how backups are done “under the hood” in the web interface.

You may cross-check that the backups are identical to the ones via the GUI using the following steps (last tested at 2025-04-22):

Download the backup via the graphical interface
Create a backup via a script
Copy both files to router
Convert both files via the command:
“nvram convert <filename1/2> > result_file1/2.txt”
Perform a diff between the two resulting text files.

The script then archives the resulting data in a tar file and sends it through the netcat command, transferring it over the network. Restore a backup file uses the same procedure as restoring an archive created in the web interface. This was last tested on 2025-04-29.

Prerequisites

The netcat command must be available on the backup server.
The router's root user must have access to the public SSH key
of the user executing the script on backup server.

Remarks

Command line arguments: backup directory, id-file and router (as IP address).
If provided, these will be used. Otherwise, the defaults will apply
(such Router IP from “ip r”).
Sometimes tar may fail. You can solve this by just cleaning. The next
cron run may do that.
All earlier backups from the same day are abandoned.
A total number of backups is kept. This number is configurable.
Older backups are deleted.

 #!/bin/bash
 
 DATE_REGEX=20[0-9][0-9][01][0-9][0123][0-9]
 TIME_REGEX=[012][0-9][0-5][0-9]
 NO_OF_DIFF_FILES_TO_BE_KEPT=10
 
 DIR2BACKUP=/home/${LOGNAME}/Router_Backups
 LOCAL_ID_FILE=/home/${LOGNAME}/.ssh/id_tomato_ecdsa
 ROUTER=`ip r | grep default | head -1 | cut -d " " -f 3`   
 
 while [[ $# -gt 0 ]]; do
      case $1 in
              -d|--dir2backup)
                      DIR2BACKUP=$2 ;;
              -i|--idfile)
                      LOCAL_ID_FILE=$2 ;;
              -r|--router)
                      ROUTER=$2 ;;
              -*|--*)
                      echo "Unknown option $1" ;;
              -h|--help)
                      echo "usage $0 <option argument> 
                      echo "options are:"
                      echo "  -d \| --dir2backup      directory to save backup,               default: ${DIR2BACKUP} "
                      echo "  -r \| --router          router ostname or IP to be saved,       default: ${ROUTER}"
                      echo "  -i \| --idfile          directory to save backuip,              default: ${ROUTER}
                      exit ;;
      esac
      shift; shift
 done
 
 BACKUPHOST=`ip r | grep "${ROUTER%1}0/24" | head -1 | cut -d " " -f 9`
 echo
 echo "Backup dir:  "${DIR2BACKUP}
 echo "id file:     "${LOCAL_ID_FILE}
 echo "Backing up:  "${ROUTER}
 echo "Backup host: "${BACKUPHOST}
 echo
 USER=root
 PORT=5555
 SCRIPT_FILE=nvram_save_cfg.sh
 PREFIX=FreshTomato
 EXT=cfg
 TRANSFER_FILENAME=config.tar
 
 # It may be, that Tomato router has no - or other, wrong - timeother or no timee
 # take date from localhost (i.e. backupserver) into backup filename
 DATE=`date +%Y%m%d_%H%M`

 pushd ${DIR2BACKUP} > /dev/null
 
 rm -f ${TRANSFER_FILENAME} 
 #
 # Thinks like
 # VAR=`nvram get os_version` 
 # seem not to work in bash via here doc, so write results into script file and source it
 # Further the individual filename is general not known, so tar it into temp file
 #
 # Kill netcat zombies
 kill -9 `ps -ef | grep -v grep | grep netcat | sed -e "s/ [ ]*/ /g" | cut -d " " -f 2` 2> /dev/null
 (netcat -l -p ${PORT} > ${TRANSFER_FILENAME}) &
 ssh ${USER}@${ROUTER} -i ${LOCAL_ID_FILE} <<ENDSSH
      rm -f ${SCRIPT_FILE} ${TRANSFER_FILENAME} ${PREFIX}_*_${DATE_REGEX}_${TIME_REGEX}.${EXT}
      echo "nvram save ${PREFIX}" >> ${SCRIPT_FILE}
      nvram get os_version | sed -e "s/ .*$//" >> ${SCRIPT_FILE}
      echo "on" >> ${SCRIPT_FILE}
      nvram get t_model_name | tr " " "_" >> ${SCRIPT_FILE}
      nvram get router_name >> ${SCRIPT_FILE}
      echo ${DATE} >> ${SCRIPT_FILE}
      sed -e "N;N;N;N;N;s/\n/_/g;s/$/.${EXT}/" -i ${SCRIPT_FILE}
      source ${SCRIPT_FILE}
      tar -cvf ${TRANSFER_FILENAME} ${PREFIX}_*_${DATE_REGEX}_${TIME_REGEX}.${EXT} > /dev/null
      cat ${TRANSFER_FILENAME} | nc ${BACKUPHOST} ${PORT}
      sleep 5 # just wait a little bit before deleting the files not needed here any more
      rm -f ${SCRIPT_FILE} ${TRANSFER_FILENAME} ${PREFIX}_*_${DATE_REGEX}_${TIME_REGEX}.${EXT}
 ENDSSH
 
 THIS_BACKUP_FILE=`tar -xvf ${TRANSFER_FILENAME} | sed -e "s/^.*${PREFIX}/${PREFIX}/"`
 if [ "${THIS_BACKUP_FILE}" ]; then
      echo "Saved on this computer in `pwd`:"
      echo ${THIS_BACKUP_FILE}
      echo
      TODAYS_BACKUP_FILES_PREFIX=${THIS_BACKUP_FILE%_*}
      ALL_BACKUP_FILES_PREFIX=${TODAYS_BACKUP_FILES_PREFIX%_*}
      # Keep only one file (the latest) per day - delete earlier file of same day
      LIST_OLD_BACKUPS_OF_TODAY=`ls ${TODAYS_BACKUP_FILES_PREFIX}_${TIME_REGEX}.${EXT} 2> /dev/null | grep -v ${THIS_BACKUP_FILE}`
      if [ "${LIST_OLD_BACKUPS_OF_TODAY}" ]; then
              echo "deleting earlier backups from today (to keep just one per day - the most recent):"
              rm -fv ${LIST_OLD_BACKUPS_OF_TODAY}
              echo
      fi
      # In total, keep only ${NO_OF_DIFF_FILES_TO_BE_KEPT} files - delete older files (of any day)
      OLDER_FILES=`ls -t ${ALL_BACKUP_FILES_PREFIX}_${DATE_REGEX}_${TIME_REGEX}.${EXT} | sed -e 1,${NO_OF_DIFF_FILES_TO_BE_KEPT}d`
      if [ "${OLDER_FILES}" ]; then
              echo "keep only ${NO_OF_DIFF_FILES_TO_BE_KEPT} in total, delete:"
              rm -fv ${OLDER_FILES}
              echo
      fi
      # delete transfer file only when tar was successful, i.e. only here
      rm ${TRANSFER_FILENAME}
 else
      echo "unknown error while untaring"
 fi
 popd > /dev/null

Table of Contents

Backup Script

Goals

Prerequisites

Remarks