Changing GID (gid>1000) to system (gid<1000)

change_group_id.sh

#!/bin/bash

#
# Program: Changing GID (gid>1000) to system (gid<1000) <change_group_id.sh>
#
# Author: Mikhail Grigorev <sleuthhound at gmail dot com>
#
# Current Version: 1.0
#
# Revision History:
#
#  Version 1.0
#    Initial Release
#
# License:
#  This program is distributed in the hope that it will be useful,
#  but WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

GROUP=mysql
DIR_LIST="/etc /var/lib/mysql /var/log/mysql"
SERVICE_NAME_LIST="mysql mysql@test1 mysql@test2"
MULTI_SERVICE_PREFIX=mysql-multi
MULTI_SERVICE_DIR="/etc/mysql-multi"

_service() {
        local SERVICE_ACTION=$1
        for SRV in ${SERVICE_NAME_LIST}; do
                echo "Service '${SRV}', execute '${SERVICE_ACTION}'"
                systemctl ${SERVICE_ACTION} ${SRV}
        done
}

_multi_service() {
        local SERVICE_ACTION=$1
        for CLUSTER in $(find ${MULTI_SERVICE_DIR} -type f -iname "*.cnf" -exec basename {} \;); do
                local M_SERVICE=${MULTI_SERVICE_PREFIX}@${CLUSTER%.*}
                echo "Service '${M_SERVICE}', execute '${SERVICE_ACTION}'"
                systemctl ${SERVICE_ACTION} ${M_SERVICE}
        done
}

OLD_G_ID=$(getent group | grep ${GROUP} | awk -F':' '{print $3}')
if [ -n "${OLD_G_ID}" ]; then
        echo "Group: ${GROUP}, GID: ${OLD_G_ID}"
        if [ ${OLD_G_ID} -ge 1000 ]; then
                echo "Init changing GID for group '${GROUP}'"
                NEW_GID=$(getent group | cut -d ":" -f 3 | grep "^1..$" | sort -n | tail -n 1 | awk '{ print $1+1 }')
                echo "Set new GID for group '${GROUP}' = ${NEW_GID}"
                read -n 1 -s -r -p "Press any key to run changing GID or press Ctrl+C to abort"
                echo ""
                _service "stop"
                #_multi_service "stop"
                echo "Changing GID..."
                groupmod -g ${NEW_GID} ${GROUP}
                echo "Changing file and directory owner..."
                find ${DIR_LIST} -group ${OLD_G_ID} -exec chgrp -h ${GROUP} {} \;
                #_multi_service "start"
                _service "start"
        else
                echo "GID of the group '${GROUP}' is less than 1000"
                exit 1
        fi
else
        echo "Group '${GROUP}' not found."
        exit 1
fi