DNSmasq DHCP Fixed IP For Ethernet And Wireless Networking

With the current mobility that laptops provide, it may be useful to unplug a laptop from an ethernet cable and take it around the house. If you wish to keep the same IP after switching network interfaces, this code may come in handy. If you're using DNSmasq for DHCP server duties, you can add this to the dnsmasq.conf file:

dhcp-host=00:aa:bb:cc:dd:e0,00:aa:bb:cc:dd:e1,pc0,192.168.0.2
dhcp-host=00:aa:bb:cc:dd:e2,pc1,192.168.0.3
dhcp-host=00:aa:bb:cc:dd:e3,pc2,192.168.0.4

DNSmasq will attribute the same IP, 192.168.0.2, to the MAC addresses 00:aa:bb:cc:dd:e0 and 00:aa:bb:cc:dd:e1, when one of the devices requests one. Be careful though, as if you're using the devices in different machines afterwards, you will loose connectivity in one of them.
The two other lines are normal dhcp-host lines, with only the single MAC address. The pc* parameter is the name that the DHCP server will assign to the machines identified by the respective MAC address.

HPC - Linking to Intel ICC/IFC Compiled Libraries

Sometimes your Linux system may contain a whole lot of mixed software that you may not want to mess with to avoid breaking a machine(or parts of it) that's running in a production environment.

In a cluster I worked at, we had a library compiled with Intel's compiler because is better performing in Intel's processors. The machine had the FFTW library compiled with ICC/IFC and upon linking a program compiled with GCC Fortran compiler, I was greeted with this error:

/usr/lib64/libfftw_mpi.so: undefined reference to `__libm_sse2_sincos'
/usr/lib64/libfftw_mpi.so: undefined reference to `_intel_fast_memcpy'
collect2: ld returned 1 exit status

They are both easy to solve, just add this line to the LDFLAGS variable in the Makefile.

-L/opt/intel/fce/COMPILER_VERSION/lib -lirc -limf

The symbol __libm_sse2_sincos is provided by libimf.a while _intel_fast_memcpy is provided by libirc.a.The program should now link without missing symbols and you should have an executable file. Sometimes the order the linked libraries are set in LDFLAGS matters, so take that into consideration if it still fails or user an alternative to the GNU linker.