I forgot something when I setup Domjudge, I didn't install judgehost. Now, I just install it, but I got error when I run:
make -C etc config
make[1]: Entering directory `/home/domjudge/etc'
make[1]: Nothing to be done for `config'.
make[1]: Leaving directory `/home/domjudge/etc'
Recursing target `judgehost' into: etc judge misc-tools
make[1]: Entering directory `/home/domjudge/etc'
make[1]: Nothing to be done for `judgehost'.
make[1]: Leaving directory `/home/domjudge/etc'
make[1]: Entering directory `/home/domjudge/judge'
gcc -fPIE -Wl,-z,relro -Wl,-z,now runguard.o /usr/lib/libm.so -o runguard
/usr/lib/libm.so: could not read symbols: File in wrong format
collect2: ld returned 1 exit status
make[1]: *** [runguard] Error 1
make[1]: Leaving directory `/home/domjudge/judge'
make: *** [judgehost] Error 1