I was first getting this issue: https://github.com/facebook/react-native/issues/10088
Then I followed this solution to resolve for that issue: https://github.com/facebook/react-native/issues/910#issuecomment-94181845
Now when I enter npm start I get [sane] Warning: Lost connection to watchman, reconnecting... Any suggestions?
Update: This started happening when I updated my MacOS to MacOS Sierra.
Update: So I tried running react-native run-ios which opens a new console window and invokes npm start. Its still gives the [sane] Warning: Lost connection to watchman, reconnecting.. warnings but its builds the bundle. So watchman connection is getting broken in between. Here is the console screenshot:
I solved this problem by following the solution provided by David but I had to do some extra steps because I already had installed watchman using brew. Here are the list of commands for the solution:
Deleting watchman (installed by brew):
$ brew install rmtree
$ brew rmtree watchman
$ sudo rm -rf /usr/local/var/run/watchman
Manually install Watchman v4.7.0 (credits to David):
$ git clone https://github.com/facebook/watchman.git
$ cd watchman
$ git checkout v4.7.0
$ ./autogen.sh
$ ./configure
$ make
$ sudo make install
Chmod your user's watchman state directory:
$ chmod 0700 /usr/local/var/run/watchman/<user>-state
run this command inside project folder
watchman watch-del-all && npm start --reset-cache
I have a simular issue and looking at the logs for Watchman I get these errors happening each time you see the "Lost Connection to Watchman" message.
2016-11-05T03:35:48,401: [listener] Watchman 4.7.0 <no build info set> starting up on Davids-Mac.local
2016-11-05T03:35:48,401: [listener] path /Users/david/Projects/react-native-test is on filesystem type hfs
2016-11-05T03:35:48,402: [listener] root /Users/david/Projects/react-native-test using watcher mechanism fsevents (auto was requested)
2016-11-05T03:35:48,406: [listener] file limit is 2560 kern.maxfilesperproc=10240
2016-11-05T03:35:48,406: [listener] raised file limit to 10240
2016-11-05T03:35:48,407: [listener] Using socket from launchd as listening socket
2016-11-05T03:35:48,934: [io 0x7f8175600ff8 /Users/david/Projects/react-native-test] PERF: {"ru_nvcsw": 0, "ru_nsignals": 0, "ru_msgrcv": 6, "ru_msgsnd": 6, "ru_inblock": 0, "ru_majflt": 0, "ru_nswap": 0, "ru_minflt": 5230, "ru_ixrss": 0, "ru_maxrss": 21405696, "system_time": 0.32367200000000002, "user_time": 0.18271599999999999, "elapsed_time": 0.53129999999999999, "pid": 9867, "ru_idrss": 0, "meta": {"root": {"watcher": "fsevents", "ticks": 2, "number": 1, "case_sensitive": false, "recrawl_count": 0, "path": "/Users/david/Projects/react-native-test"}}, "version": "4.7.0", "ru_oublock": 0, "ru_nivcsw": 112, "start_time": 1478316948.403332, "description": "full-crawl"}
2016-11-05T03:35:48,935: [io 0x7f8175600ff8 /Users/david/Projects/react-native-test] crawl complete
2016-11-05T03:35:49,029: [client=0x7f8176a00038:stm=0x7f8176a00000] Unilateral payload for sub sane-sub {"settled": true}
Terminating due to signal 11 Segmentation fault generated by pid=0 uid=0. address not mapped to object (0x0)
0 watchman 0x0000000105973759 _ZL13crash_handleriP9__siginfoPv + 347
1 libsystem_platform.dylib 0x00007fffa2292bba _sigtramp + 26
2 ??? 0x00007f81756000c0 0x0 + 140193996734656
3 watchman 0x000000010596f9b2 _ZN6detail22estimateSpaceToReserveIPKcJA3_cA28_c8w_stringA2_cPcS6_EEEmmRKT_DpRKT0_ + 109
4 watchman 0x000000010596f815 _ZN8w_string5buildIJPcRA4_KcPS2_RA3_S2_RA28_S2_RS_RA2_S2_RS1_SC_EEES_DpOT_ + 121
5 watchman 0x000000010599b4cb _ZN8watchman3Log3logIJRA28_KcR8w_stringRA2_S2_RPcS8_EEEvNS_8LogLevelEDpOT_ + 183
6 watchman 0x000000010599a6e0 _ZNSt3__114__thread_proxyINS_5tupleIJZL15make_new_clientP15watchman_streamE3$_0EEEEEPvS6_ + 952
7 libsystem_pthread.dylib 0x00007fffa229cabb _pthread_body + 180
8 libsystem_pthread.dylib 0x00007fffa229ca07 _pthread_body + 0
9 libsystem_pthread.dylib 0x00007fffa229c231 thread_start + 13
UPDATE: Ok, found a solution which so far seems to work. I uninstall watchman completely, then build it from source using the following which seems to work fine (any attempt at installing via brew causes the problems above but this works):
$ git clone https://github.com/facebook/watchman.git
$ cd watchman
$ git checkout v4.7.0 # the latest stable release
$ ./autogen.sh
$ ./configure
$ make
$ sudo make install
来源：https://stackoverflow.com/questions/40414166/react-native-npm-start-with-watchman-error