caught SIGTERM, shutting down

oogoogle

军哥，ubuntu 16.04 安装了 LNMPA，在 /home/wwwlog下面的error_log日志里每天都有这些错误：

[Wed Jun 13 01:33:28.891381 2018] [mpm_event:notice] [pid 4469:tid 139743628359424] AH00491: caught SIGTERM, shutting down
[Wed Jun 13 01:33:32.072377 2018] [mpm_event:notice] [pid 21641:tid 139899214501632] AH00489: Apache/2.4.33 (Unix) OpenSSL/1.0.2g configured -- resuming normal operations
[Wed Jun 13 01:33:32.072571 2018] [core:notice] [pid 21641:tid 139899214501632] AH00094: Command line: '/usr/local/apache/bin/httpd'
[Wed Jun 13 02:56:03.143116 2018] [mpm_event:notice] [pid 21641:tid 139899214501632] AH00491: caught SIGTERM, shutting down
[Wed Jun 13 02:56:07.305291 2018] [mpm_event:notice] [pid 22738:tid 139774121412352] AH00489: Apache/2.4.33 (Unix) OpenSSL/1.0.2g configured -- resuming normal operations
[Wed Jun 13 02:56:07.305457 2018] [core:notice] [pid 22738:tid 139774121412352] AH00094: Command line: '/usr/local/apache/bin/httpd'

请问是什么原因造成的，如何修正？

licess

这都是notice没错误