Q:

npm install grpc failed

enviroment: node version v8.9.3 npm >5.x

start install grpc by npm, i got some errors
    npm install -g grpc
the errors:
gyp ERR!  build error
gyp ERR!  stack Error: `make` failed with exit code: 2
gyp ERR!  stack     at ChildProcess.onExit 
(/Users/yuham/.nvm/versions/node/v8.9.3/lib/node_modules/node-
gyp/lib/build.js:258:23)
gyp ERR!  stack     at emitTwo (events.js:126:13)
gyp ERR!  stack     at ChildProcess.emit (events.js:214:7)
gyp ERR!  stack     at Process. ChildProcess._handle.onexit 
(internal/child_process.js:198:12)
gyp ERR!  System Darwin 17.2.0
...
gyp ERR!  cwd /Users/yuham/.nvm/versions/node/v8.9.3/lib/node_modules/grpc
gyp ERR!  node -v v8.9.3
gyp ERR!  node-gyp -v v3.6.2
gyp ERR!  not ok
node-pre-gyp ERR!  build error
node-pre-gyp ERR!  stack Error: Failed to execute 
...
node-pre-gyp ERR!  stack     at ChildProcess.<anonymous> 
(/Users/yuham/.nvm/versions/node/v8.9.3/lib/node_modules/
grpc/node_modules/node-
pre-gyp/lib/util/compile.js:83:29)
node-pre-gyp ERR!  stack     at emitTwo (events.js:126:13)
node-pre-gyp ERR!  stack     at ChildProcess.emit (events.js:214:7)
node-pre-gyp ERR!  stack     at maybeClose (internal/child_process.js:925:16)
node-pre-gyp ERR!  stack     at Process. ChildProcess._handle.onexit 
(internal/child_process.js:209:5)
node-pre-gyp ERR!  System Darwin 17.2.0
node-pre-gyp ERR!  command "/Users/yuham/.nvm/versions/node/v8.9.3/bin/node" 
"/Users/yuham/.nvm/versions/node/v8.9.3/lib/node_modules/
grpc/node_modules/.bin/node-pre-gyp" "install" "--fallback-to-build" "--
library=static_library"
node-pre-gyp ERR!  cwd 
/Users/yuham/.nvm/versions/node/v8.9.3/lib/node_modules/grpc
node-pre-gyp ERR!  node -v v8.9.3
node-pre-gyp ERR!  node-pre-gyp -v v0.6.38
node-pre-gyp ERR!  not ok
Failed to execute '/Users/yuham/.nvm/versions/node/v8.9.3/bin/node 
/Users/yuham/.nvm/versions/node/v8.9.3/lib/node_modules/node-gyp/bin/node-
gyp.js build --fallback-to-build --library=static_library --
module=/Users/yuham/.nvm/versions/node/v8.9.3/lib/node_modules/
grpc/src/node/extension_binary/node-v57-darwin-x64/grpc_node.node --
module_name=grpc_node --
module_path=/Users/yuham/.nvm/versions/node/v8.9.3/lib/node_modules/
grpc/src/node/extension_binary/node-v57-darwin-x64' (1)

npm ERR!  code ELIFECYCLE
npm ERR!  errno 1
npm ERR!  grpc@1.6.6 install: `node-pre-gyp install --fallback-to-build --
library=static_library`
npm ERR!  Exit status 1
npm ERR! 
npm ERR!  Failed at the grpc@1.6.6 install script. 
npm ERR!  This is probably not a problem with npm.  There is likely additional 
logging output above. 

npm ERR!  A complete log of this run can be found in:

i'm try to install diffirent version of grpc, but get the same result
while this error caused by node-pre-gyp or node-gyp?  my computer system is osx --lts.  i can't find any good idea or solution
how to fix it?  

A:

run this command, it will work
npm install -g xxx --unsafe-perm

but i don't understand what '--unsafe-perm' mean?