Import your backup gpg key into root’s gnupg keystore.

mkdir -p /var/backup

cat << EOF >>/etc/cron.daily/backup
#!/bin/bash

#set -x
umask 077

GPG_KEY=<gpg key>
TMPDIR=/tmp
USER=root
DSTDIR=/var/backup/$HOSTNAME
DBFILE=`hostname`.sql
BACKUP_DIRS='/etc /var/spool/cron'

# backup piwik mysql database
mysqldump --all-databases \
        --events --single-transaction --routines >${TMPDIR}/${DBFILE} && \
        chown ${USER}:${USER} ${TMPDIR}/${DBFILE} && \
        cat ${TMPDIR}/${DBFILE} | gpg --no-tty --encrypt \
        -r ${GPG_KEY} - >${DSTDIR}/${DBFILE}.gpg" && \
        rm ${TMPDIR}/$DBFILE || exit 3

tar cfz ${TMPDIR}/${HOSTNAME}.tgz $BACKUP_DIRS &>/dev/null && \
        chown ${USER}:${USER} ${TMPDIR}/${HOSTNAME}.tgz && \
        cat ${TMPDIR}/${HOSTNAME}.tgz | gpg --no-tty --encrypt \
        -r ${GPG_KEY} - >${DSTDIR}/${HOSTNAME}.tgz.gpg && \
        rm ${TMPDIR}/${HOSTNAME}.tgz || exit 3

exit 0
EOF

chmod 700 /etc/cron.daily/backup

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