What is 'Signal 15' ?

https://access.redhat.com/solutions/737033

环境

• Red Hat Enterprise Linux 5
• Red Hat Enterprise Linux 6

问题

• Server unexpected reboot.
• System is getting rebooted with 'Signal 15' :

Raw

shutdown: shutting down for system reboot
     init: Switching to runlevel: 6
    [...]
     exiting on signal 15
     syslogd 1.4.1: restart.
     syslog: syslogd startup succeeded
           

• What is this signal 15 ?

决议

Signal 15 is a SIGTERM (see "kill -l" for a complete list). It's the way most programs are gracefully terminated, and is relatively normal

behaviour.This indicates system has delivered a SIGTERM to the processes. This is usually at the request of some other process (via kill()) but could also be sent by your process to itself (using raise()). This signal requests an orderly shutdown of process or system itself.

Raw

$ kill -l
 1) SIGHUP   2) SIGINT   3) SIGQUIT  4) SIGILL   5) SIGTRAP
 6) SIGABRT  7) SIGBUS   8) SIGFPE   9) SIGKILL 10) SIGUSR1
11) SIGSEGV 12) SIGUSR2 13) SIGPIPE 14) SIGALRM 15) SIGTERM
16) SIGSTKFLT   17) SIGCHLD 18) SIGCONT 19) SIGSTOP 20) SIGTSTP
21) SIGTTIN 22) SIGTTOU 23) SIGURG  24) SIGXCPU 25) SIGXFSZ
26) SIGVTALRM   27) SIGPROF 28) SIGWINCH    29) SIGIO   30) SIGPWR
31) SIGSYS  34) SIGRTMIN    35) SIGRTMIN+1  36) SIGRTMIN+2  37) SIGRTMIN+3
38) SIGRTMIN+4  39) SIGRTMIN+5  40) SIGRTMIN+6  41) SIGRTMIN+7  42) SIGRTMIN+8
43) SIGRTMIN+9  44) SIGRTMIN+10 45) SIGRTMIN+11 46) SIGRTMIN+12 47) SIGRTMIN+13
48) SIGRTMIN+14 49) SIGRTMIN+15 50) SIGRTMAX-14 51) SIGRTMAX-13 52) SIGRTMAX-12
53) SIGRTMAX-11 54) SIGRTMAX-10 55) SIGRTMAX-9  56) SIGRTMAX-8  57) SIGRTMAX-7
58) SIGRTMAX-6  59) SIGRTMAX-5  60) SIGRTMAX-4  61) SIGRTMAX-3  62) SIGRTMAX-2
63) SIGRTMAX-1  64) SIGRTMAX    
           

• The real question is "Who/what is sending the SIGTERM?", Please refer the below mentioned articles for the same.

  How to find which user has rebooted the system?

  How to find out who sent the 'signal-15' ?