ddwrt-dhcp-lease-persist.sh

#!/bin/sh
#DEBUG=; set -x # comment/uncomment to disable/enable debug mode

#          name: ddwrt-dhcp-lease-persist.sh
#       version: 1.0.4, 29-jun-2019, by eibgrad
#       purpose: make dhcp leases persistent w/ external storage (e.g., usb)
#   script type: startup (autostart)
#  installation:
#    1. enable jffs2 (administration->jffs2)
#    2. enable syslogd (services->services->system log)
#    3. use shell (telnet/ssh) to execute one of the following commands:
#         curl -kLs bit.ly/ddwrt-installer|tr -d '\r'|sh -s MxA19W1M startup
#       or
#         wget -qO - bit.ly/ddwrt-installer|tr -d '\r'|sh -s MxA19W1M startup
#    4. modify options using vi editor (optional):
#         vi /jffs/etc/config/ddwrt-dhcp-lease-persist.startup
#    5. reboot
{
# ------------------------------ BEGIN OPTIONS ------------------------------- #

# external storage mounting point (default=/opt)
MOUNT="/opt"
#MOUNT="/tmp/mnt/sda1" # (hd0,0), (drive1,partition1)
#MOUNT="/tmp/mnt/sda2" # (hd0,1), (drive1,partition2)

# external storage directory (default=/ (root))
DIR="$MOUNT"
#DIR="$MOUNT/ddwrt/system_files" # example of non-root storage

# external storage file
FILE="$DIR/dnsmasq.leases"

# max time (in secs) to wait for external storage to be mounted (0=infinite)
MAX_WAIT=120

# ------------------------------- END OPTIONS -------------------------------- #

# ---------------------- DO NOT CHANGE BELOW THIS LINE ----------------------- #

# start the timer
start_time=$(date +%s)

# wait for the external storage to be mounted
while :; do
    # determine if external storage is mounted
    df | grep -Eq "[[:space:]]+$MOUNT\$" && break

    if [ $MAX_WAIT -gt 0 ]; then
        # exit upon reaching execution limit
        [ $(($(date +%s) - start_time)) -ge $MAX_WAIT ] && exit 1
    fi

    sleep 3
done

# wait for dhcp server to appear in process table
while ! pidof dnsmasq >/dev/null 2>&1; do sleep 3; done

# stop dhcp server
stopservice dnsmasq && sleep 3

# create persistent directory as necessary
[ -d $DIR ] || mkdir -p $DIR

# copy dhcp leases (if any) to persistent file
[ -f $FILE ] || cp /tmp/dnsmasq.leases $FILE

# force dhcp server to use persistent file
ln -sf $FILE /tmp/dnsmasq.leases

# restart dhcp server
restart dnsmasq

exit 0

} 2>&1 | logger $([ ${DEBUG+x} ] && echo "-p user.debug") \
    -t $(echo $(basename $0) | grep -Eo '^.{0,23}')[$$] &