Ubuntu没有设置软件源会出现一些问题

在Ubuntu中，如果没有设置软件源，make会出现类似以下情况：
E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).
Install these packages without verification [y/N]?
E: Some packages could not be authenticated

另一个例子：
a52 make 的错误
gcc -shared bitstream.lo imdct.lo bit_allocate.lo parse.lo downmix.lo -lm -Wl,-soname -Wl,liba52.so.0 -o .libs/liba52.so.0.0.0
/usr/bin/ld: bitstream.lo: relocation R_X86_64_32 against `a local symbol' can not be used when making a shared object; recompile with -fPIC
bitstream.lo: could not read symbols: Bad value
collect2: ld returned 1 exit status
make[1]: *** [liba52.la] Error 1
make[1]: Leaving directory `/home/a52dec-0.7.4/liba52'
make: *** [all-recursive] Error 1
至此就停止了。

所以，一定要设置哦！