AirOS uses udhcpc for the DHCP client on Ubiquiti Radios. To renew the DHCP address you can kill the udhcpc process and it’ll automatically restart and get a new address.
Renew DHCP lease
Kill udhcpc with the following command.
Print info about the DHCP lease. May need to change “info.br1” to “info.eth0” or some other interface.
XW.v6.2.0# cat /etc/udhcpc/info.br1 u_interface="br1" u_broadcast="" u_subnet="255.255.255.0" u_ip="10.93.0.10" u_router="10.93.0.1" u_dns="22.214.171.124 126.96.36.199" u_hostname="" u_serverid="10.93.0.1" u_domain="" u_leasetime=600 u_timestamp="1143249941" u_started=1142593 u_pid=936 XW.v6.2.0#
Command arguments that udhcp is run with. Info was collected by running the “ps | grep udhcp” command. Note that the interface “eth0” can be different if the device is in bridge mode.
/sbin/udhcpc -f -i eth0 -s /etc/udhcpc/udhcpc -p /var/run/udhcpc.eth0.pid -h device_name
udhcpc help output
XW.v6.2.0# udhcpc --help BusyBox v1.24.2 (2019-07-03 11:13:35 EEST) multi-call binary. Usage: udhcpc [-fbqvRB] [-t N] [-T SEC] [-A SEC/-n] [-i IFACE] [-s PROG] [-p PIDFILE] [-oC] [-r IP] [-V VENDOR] [-F NAME] [-x OPT:VAL]... [-O OPT]... -i,--interface IFACE Interface to use (default eth0) -s,--script PROG Run PROG at DHCP events (default /usr/share/udhcpc/default.script) -p,--pidfile FILE Create pidfile -B,--broadcast Request broadcast replies -t,--retries N Send up to N discover packets (default 3) -T,--timeout SEC Pause between packets (default 3) -A,--tryagain SEC Wait if lease is not obtained (default 20) -n,--now Exit if lease is not obtained -q,--quit Exit after obtaining lease -R,--release Release IP on exit -f,--foreground Run in foreground -b,--background Background if lease is not obtained -S,--syslog Log to syslog too -r,--request IP Request this IP address -o,--no-default-options Don't request any options (unless -O is given) -O,--request-option OPT Request option OPT from server (cumulative) -x OPT:VAL Include option OPT in sent packets (cumulative) Examples of string, numeric, and hex byte opts: -x hostname:bbox - option 12 -x lease:3600 - option 51 (lease time) -x 0x3d:0100BEEFC0FFEE - option 61 (client id) -F,--fqdn NAME Ask server to update DNS mapping for NAME -V,--vendorclass VENDOR Vendor identifier (default 'udhcp VERSION') -C,--clientid-none Don't send MAC as client identifier -v Verbose Signals: USR1 Renew lease USR2 Release lease XW.v6.2.0#
Note that you can also send a signal to the PID of udhcpc and have it renew the address. To do that use the following command, replacing pidofudhcpc to pid of udhcp.
kill -s USR1 pidofudhcpc
or use the following command to find the pid for you.
kill -s SIGUSR1 $(pgrep udhcpc)