mongodb crashed with the error or permission denied Our mongodb server was running for the last two months without any error. Suddenly it crashed and below is the log.

2017-08-11T13:41:41.320+0100 E STORAGE  [thread1] WiredTiger (13) [1502455301:320924][1281:0x7f11bce8e700], log-server: /var/lib/mongo/journal: opendir: Permission denied
2017-08-11T13:41:41.320+0100 E STORAGE  [thread1] WiredTiger (13) [1502455301:320991][1281:0x7f11bce8e700], log-server: dirlist journal prefix WiredTigerPreplog: Permission denied
2017-08-11T13:41:41.321+0100 E STORAGE  [thread1] WiredTiger (13) [1502455301:321013][1281:0x7f11bce8e700], log-server: log pre-alloc server error: Permission denied
2017-08-11T13:41:41.321+0100 E STORAGE  [thread1] WiredTiger (13) [1502455301:321021][1281:0x7f11bce8e700], log-server: log server error: Permission denied
2017-08-11T13:41:42.000+0100 I -        [ftdc] Assertion: 13538:couldn't open [/proc/1281/stat] errno:13 Permission denied
2017-08-11T13:41:42.000+0100 W FTDC     [ftdc] Uncaught exception in 'Location13538 couldn't open [/proc/1281/stat] errno:13 Permission denied' in full-time diagnostic data capture subsystem. Shutting down the full-time diagnostic data capture subsystem.
2017-08-11T13:41:50.006+0100 I NETWORK  [initandlisten] connection accepted from 127.0.0.1:45196 #205521 (23 connections now open)
2017-08-11T13:41:50.006+0100 I NETWORK  [conn205521] end connection 127.0.0.1:45196 (22 connections now open)
2017-08-11T13:42:36.004+0100 E STORAGE  [thread2] WiredTiger (13) [1502455356:4361][1281:0x7f11bb68b700], file:WiredTiger.wt, WT_SESSION.checkpoint: WiredTiger.turtle: fstat: Permission denied
2017-08-11T13:42:36.004+0100 E STORAGE  [thread2] WiredTiger (13) [1502455356:4466][1281:0x7f11bb68b700], checkpoint-server: checkpoint server error: Permission denied
2017-08-11T13:42:36.004+0100 E STORAGE  [thread2] WiredTiger (-31804) [1502455356:4480][1281:0x7f11bb68b700], checkpoint-server: the process must exit and restart: WT_PANIC: WiredTiger library panic
2017-08-11T13:42:36.004+0100 I -        [thread2] Fatal Assertion 28558
2017-08-11T13:42:36.004+0100 I -        [thread2] 

***aborting after fassert() failure


Please tell me why it happened and what should I do to avoid this crash in future. I am using mongodb version 3.2. How come the file permission changed while the server is running.
It's not mongodb fault. Your system went to &quot;read only&quot; mode.
You can see errors on that log file. Positive is that system managed to write that information to log file because it makes easier to debug this problem.

/var/lib/mongo/journal: opendir: Permission denied
couldn't open [/proc/1281/stat] errno:13 Permission denied

Check /var/log/syslog (or /messages) for more info, something fatal happened on that node and it's operating system!