The DHCP client packaged with BusyBox is udhcpc . It negotiates a lease with the DHCP server and executes a script when it is obtained or lost. There are four possible arguments to this script: deconfig : The script should put the interface in an up but deconfigured state. bound : The script should configure the interface and set any other relevant parameters. renew : This is used when a lease is renewed. IP address does not change but other parameters may change. nak : This happens when a NAK packet is received from the DHCP server. Network parameters are passed to the script via environment variables. Ubuntu documents that the default script is at /etc/udhcpc/default.script . For OpenWRT, it is located at /usr/share/udhcpc/default.script ....

Wifi router firmware has three parts: CFE (Common Firmware Environment): The CFE (aka boot loader) performs low-level initializations and is used to bootstrap the OS. NVRAM (Non-volatile RAM): NVRAM can hold its contents even when the main power source is lost. Configuration settings are stored in NVRAM. When you do a 30-30-30 hard reset, you are resetting the NVRAM to factory defaults. Kernel : The kernel is the OS of the router. It is stored in the onboard Flash chip. From DD-WRT forum (the peacock thread): You can erase the nvram. You can reflash the kernel. But if you don't have a CFE file FOR your specific model of router, you are pooched. Links: TFTP flash CFE Backup JTAG-adapter JTAG Serial Recovery

If Command Extensions are enabled (which is enabled by default), then there are several dynamic environment variables that can be expanded but which don't show up in the list of variables displayed by SET . These variable values are computed dynamically each time the value of the variable is expanded (but see example below). If the user explicitly defines a variable with one of these names, then that definition will override the dynamic one described below: %CD% - expands to the current directory string. %DATE% - expands to current date using same format as DATE command. %TIME% - expands to current time using same format as TIME command. %RANDOM% - expands to a random decimal number between 0 and 32767. %ERRORLEVEL% - expands to the...

%PATH:str1=str2% would expand the PATH environment variable, substituting each occurrence of " str1 " in the expanded result with " str2 ". " str2 " can be the empty string to effectively delete all occurrences of " str1 " from the expanded output. " str1 " can begin with an asterisk, in which case it will match everything from the beginning of the expanded output to the first occurrence of the remaining portion of str1. %PATH:~10,5% would expand the PATH environment variable, and then use only the 5 characters that begin at the 11th (offset 10) character of the expanded result. If the length is not specified, then it defaults to the remainder of the variable value. If either number (offset or length) is negative,...

Turn off MS-DOS style path warnings with cygwin utilities. C:\MyWorks>diff C:\local\utils\MyClass.class C:\Fi...