Big Endian systems are becoming rare as time goes by. However, you may find the need to know the endianess of your distro useful. lscpu is the command you need.
Below is an output example:
$ lscpu Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Byte Order: Little Endian CPU(s): 4 On-line CPU(s) list: 0-3 Thread(s) per core: 2 Core(s) per socket: 2 Socket(s): 1 NUMA node(s): 1 Vendor ID: GenuineIntel CPU family: 6 Model: 61 Model name: Intel(R) Core(TM) i5-5300U CPU @ 2.30GHz Stepping: 4 CPU MHz: 2284.816 CPU max MHz: 2900.0000 CPU min MHz: 500.0000 BogoMIPS: 4589.49
…and a big endian one:
$ lscpu Architecture: ppc64 CPU op-mode(s): 32-bit, 64-bit Byte Order: Big Endian CPU(s): 8 On-line CPU(s) list: 0-7 Thread(s) per core: 8 Core(s) per socket: 1 Socket(s): 1 NUMA node(s): 1 Model: IBM pSeries (emulated by qemu) L1d cache: 64K L1i cache: 32K NUMA node0 CPU(s): 0-7