make: Entering directory `/usr/src/linux-headers-4.4.0-142-generic'
  INSTALL /home/user/kernrk/kernrk.ko
At main.c:222:
- SSL error:02001002:system library:fopen:No such file or directory: bss_file.c:169
- SSL error:2006D080:BIO routines:BIO_new_file:no such file: bss_file.c:172
sign-file: certs/signing_key.pem: No such file or directory
  DEPMOD  4.4.0-142-generic
make: Leaving directory `/usr/src/linux-headers-4.4.0-142-generic'