• Httpd启动报错 Couldn‘t create the ssl-cache 的解决办法

     测试环境：

    Server version: Apache/2.4.6 (CentOS)
    Server built:   Nov 10 2021 14:26:31

            注意，httpd的版本号是2.4.6。之前重启都正常的，突然就不能启动了，查看httpd的日志：/var/log/httpd/error.log日志，发现如下错误信息：

    [Wed Aug 17 15:43:26.756580 2022] [suexec:notice] [pid 31792] AH01232: suEXEC mechanism enabled (wrapper: /usr/sbin/suexec)
    [Wed Aug 17 15:43:26.757096 2022] [core:emerg] [pid 31792] (28)No space left on device: AH00023: Couldn't create the ssl-cache mutex
    AH00016: Configuration Failed

    如果不想继续了解后续的内容，则执行以下语句，问题即可解决： 

    ipcs -s | grep apache | awk '{ print $2 }' | xargs -n 1 ipcrm -s

    解释：

    ipcs： 该命令用于检查多进程间通信，包括共享内存、消息队列、信号量等。

    ipcrm：该命令则用于删除一个或更多的消息队列、信号量集或者共享内存标识。

    那么，总结一句就是查出apache进程尚未释放的信号量，然后将其删除。

    怀着好奇，我们先不执行执行上面的命令，先研究下错误是如何抛出来的。

    执行ipcs命令，至于为什么要执行这个命令，我也不懂，网上查的，以后有机会再深入了解吧。

    ipcs

    查看输出的内容，如下：

    1. [root@localhost /root]# ipcs
    2.  
    3. ------ Message Queues --------
    4. key        msqid      owner      perms      used-bytes   messages
    5.  
    6. ------ Shared Memory Segments --------
    7. key        shmid      owner      perms      bytes      nattch     status
    8. 0x0113aa67 393216     root       600        1000       0
    9. 0x0113ec74 425985     root       600        1000       0
    10. 0x01138f71 458754     root       600        1000       0
    11. 0x01130890 688131     root       600        1000       0
    12. 0x01133bd1 753668     root       600        1000       0
    13. 0x011319cc 983045     root       600        1000       0
    14. 0x0113e57e 1015814    root       600        1000       0
    15. 0x0113b4e8 1114119    root       600        1000       0
    16. 0x0113eede 1146888    root       600        1000       0
    17. 0x0113385b 1179657    root       600        1000       0
    18. 0x0113ddcf 1212426    root       600        1000       0
    19. 0x011330a7 1409035    root       600        1000       0
    20. 0x0113aef1 1441804    root       600        1000       0
    21. 0x0113f883 1474573    root       600        1000       0
    22. 0x01137a77 1835022    root       600        1000       0
    23. 0x0113a3f7 2949135    root       600        1000       0
    24. 0x0113d3ff 3178512    root       600        1000       0
    25. 0x0113bc22 3342353    root       600        1000       0
    26. 0x0113cffb 3375122    root       600        1000       0
    27. 0x0113fd23 3407891    root       600        1000       0
    28. 0x0113054e 3833876    root       600        1000       0
    29.  
    30. ------ Semaphore Arrays --------
    31. key        semid      owner      perms      nsems
    32. 0x00000000 3211264    apache     600        1
    33. 0x00000000 3244033    apache     600        1
    34. 0x00000000 3178498    apache     600        1
    35. 0x00000000 3276803    apache     600        1
    36. 0x00000000 3309572    apache     600        1
    37. 0x00000000 3342341    apache     600        1
    38. 0x00000000 3473414    apache     600        1
    39. 0x00000000 3506183    apache     600        1
    40. 0x00000000 3440648    apache     600        1
    41. 0x00000000 3538953    apache     600        1
    42. 0x00000000 3571722    apache     600        1
    43. 0x00000000 3604491    apache     600        1
    44. 0x00000000 3735564    apache     600        1
    45. 0x00000000 3768333    apache     600        1
    46. 0x00000000 3702798    apache     600        1
    47. 0x00000000 3801103    apache     600        1
    48. 0x00000000 3833872    apache     600        1
    49. 0x00000000 3866641    apache     600        1
    50. 0x00000000 5570578    apache     600        1
    51. 0x00000000 5603347    apache     600        1
    52. 0x00000000 5537812    apache     600        1
    53. 0x00000000 5636117    apache     600        1
    54. 0x00000000 5668886    apache     600        1
    55. 0x00000000 5701655    apache     600        1
    56. 0x00000000 6094872    apache     600        1
    57. 0x00000000 6127641    apache     600        1
    58. 0x00000000 6062106    apache     600        1
    59. 0x00000000 6160411    apache     600        1
    60. 0x00000000 6193180    apache     600        1
    61. 0x00000000 6225949    apache     600        1
    62. 0x00000000 7831582    apache     600        1
    63. 0x00000000 7864351    apache     600        1
    64. 0x00000000 7798816    apache     600        1
    65. 0x00000000 7897121    apache     600        1
    66. 0x00000000 7929890    apache     600        1
    67. 0x00000000 7962659    apache     600        1
    68. 0x00000000 8093732    apache     600        1
    69. 0x00000000 8126501    apache     600        1
    70. 0x00000000 8060966    apache     600        1
    71. 0x00000000 8159271    apache     600        1
    72. 0x00000000 8192040    apache     600        1
    73. 0x00000000 8224809    apache     600        1
    74. 0x00000000 8880170    apache     600        1
    75. 0x00000000 8912939    apache     600        1
    76. 0x00000000 8847404    apache     600        1
    77. 0x00000000 8945709    apache     600        1
    78. 0x00000000 8978478    apache     600        1
    79. 0x00000000 9011247    apache     600        1
    80. 0x00000000 9142320    apache     600        1
    81. 0x00000000 9175089    apache     600        1
    82. 0x00000000 9109554    apache     600        1
    83. 0x00000000 9207859    apache     600        1
    84. 0x00000000 9240628    apache     600        1
    85. 0x00000000 9273397    apache     600        1
    86. 0x00000000 9404470    apache     600        1
    87. 0x00000000 9437239    apache     600        1
    88. 0x00000000 9371704    apache     600        1
    89. 0x00000000 9470009    apache     600        1
    90. 0x00000000 9502778    apache     600        1
    91. 0x00000000 9535547    apache     600        1
    92. 0x00000000 9666620    apache     600        1
    93. 0x00000000 9699389    apache     600        1
    94. 0x00000000 9633854    apache     600        1
    95. 0x00000000 9732159    apache     600        1
    96. 0x00000000 9764928    apache     600        1
    97. 0x00000000 9797697    apache     600        1
    98. 0x00000000 11141186   apache     600        1
    99. 0x00000000 11173955   apache     600        1
    100. 0x00000000 11108420   apache     600        1
    101. 0x00000000 11206725   apache     600        1
    102. 0x00000000 11239494   apache     600        1
    103. 0x00000000 11272263   apache     600        1
    104. 0x00000000 11403336   apache     600        1
    105. 0x00000000 11436105   apache     600        1
    106. 0x00000000 11370570   apache     600        1
    107. 0x00000000 11468875   apache     600        1
    108. 0x00000000 11501644   apache     600        1
    109. 0x00000000 11534413   apache     600        1
    110. 0x00000000 11665486   apache     600        1
    111. 0x00000000 11698255   apache     600        1
    112. 0x00000000 11632720   apache     600        1
    113. 0x00000000 11731025   apache     600        1
    114. 0x00000000 11763794   apache     600        1
    115. 0x00000000 11796563   apache     600        1
    116. 0x00000000 14450772   apache     600        1
    117. 0x00000000 14483541   apache     600        1
    118. 0x00000000 14418006   apache     600        1
    119. 0x00000000 14516311   apache     600        1
    120. 0x00000000 14549080   apache     600        1
    121. 0x00000000 14581849   apache     600        1
    122. 0x00000000 23068762   apache     600        1
    123. 0x00000000 23101531   apache     600        1
    124. 0x00000000 23035996   apache     600        1
    125. 0x00000000 23134301   apache     600        1
    126. 0x00000000 23167070   apache     600        1
    127. 0x00000000 23199839   apache     600        1
    128. 0x00000000 24805472   apache     600        1
    129. 0x00000000 24838241   apache     600        1
    130. 0x00000000 24772706   apache     600        1
    131. 0x00000000 24871011   apache     600        1
    132. 0x00000000 24903780   apache     600        1
    133. 0x00000000 24936549   apache     600        1
    134. 0x00000000 26116198   apache     600        1
    135. 0x00000000 26148967   apache     600        1
    136. 0x00000000 26083432   apache     600        1
    137. 0x00000000 26181737   apache     600        1
    138. 0x00000000 26214506   apache     600        1
    139. 0x00000000 26247275   apache     600        1
    140. 0x00000000 26378348   apache     600        1
    141. 0x00000000 26411117   apache     600        1
    142. 0x00000000 26345582   apache     600        1
    143. 0x00000000 26443887   apache     600        1
    144. 0x00000000 26476656   apache     600        1
    145. 0x00000000 26509425   apache     600        1
    146. 0x00000000 26640498   apache     600        1
    147. 0x00000000 26673267   apache     600        1
    148. 0x00000000 26607732   apache     600        1
    149. 0x00000000 26706037   apache     600        1
    150. 0x00000000 26738806   apache     600        1
    151. 0x00000000 26771575   apache     600        1
    152. 0x00000000 29851768   apache     600        1
    153. 0x00000000 29884537   apache     600        1
    154. 0x00000000 29819002   apache     600        1
    155. 0x00000000 29917307   apache     600        1
    156. 0x00000000 29950076   apache     600        1
    157. 0x00000000 29982845   apache     600        1

    通过上面的输出内容，是不是发现有很多apache进程对应的信号量(Semaphore)。

    再统计一下，apache的Semaphore共有多少个：

    1. [root@localhost /root]# ipcs | grep apache | wc -l
    2. 126

    输出126，但这个数字又能说明什么呢，系统默认的上限又是多少呢，带着这个疑问，输入以下命令，获取系统的默认设置：

    ipcs -l

     执行结果如下：

    1. [root@localhost /root]# ipcs -l
    2.  
    3. ------ Messages Limits --------
    4. max queues system wide = 32768
    5. max size of message (bytes) = 8192
    6. default max size of queue (bytes) = 16384
    7.  
    8. ------ Shared Memory Limits --------
    9. max number of segments = 4096
    10. max seg size (kbytes) = 18014398509465599
    11. max total shared memory (kbytes) = 18014398442373116
    12. min seg size (bytes) = 1
    13.  
    14. ------ Semaphore Limits --------
    15. max number of arrays = 128
    16. max semaphores per array = 250
    17. max semaphores system wide = 32000
    18. max ops per semop call = 32
    19. semaphore max value = 32767

            根据上下文对比，我们只需要关心Semaphore Limits 这部分，从上图可以看到，Semaphore Arrays 默认的上限是128，前面我们统计出来已经存在126个了。因此，大胆推测，启动httpd的时候新增的Semaphore Arrays 超过了128，导致错误出现。

            接下来，我们验证一下启动httpd之后，Semaphore Arrays一共会有多少个。启动之前，需要执行前面所提的命令，先将所有的Semaphore清除掉才能启动成功。

    启动成功之后，查看httpd的状态：

    1. [root@localhost ~]# systemctl start httpd
    2. [root@localhost ~]# systemctl status httpd
    3. ● httpd.service - The Apache HTTP Server
    4.    Loaded: loaded (/usr/lib/systemd/system/httpd.service; enabled; vendor preset: disabled)
    5.    Active: active (running) since Thu 2022-07-21 18:17:27 CST; 3 weeks 6 days ago
    6.      Docs: man:httpd(8)
    7.            man:apachectl(8)
    8.  Main PID: 20907 (httpd)
    9.    Status: "Total requests: 0; Current requests/sec: 0; Current traffic:   0 B/sec"
    10.    CGroup: /system.slice/httpd.service
    11.            ├─ 7453 /usr/sbin/httpd -DFOREGROUND
    12.            ├─ 7454 /usr/sbin/httpd -DFOREGROUND
    13.            ├─ 7455 /usr/sbin/httpd -DFOREGROUND
    14.            ├─ 7456 /usr/sbin/httpd -DFOREGROUND
    15.            ├─ 7457 /usr/sbin/httpd -DFOREGROUND
    16.            └─20907 /usr/sbin/httpd -DFOREGROUND
    17.  
    18.

    从上面的输出可以看到，启动之后，开启了6个进程，一个父进程（pid=20907），5个子进程。也可以通过ps -ef|grep httpd 命令查看，得到的还是6个进程。

    1. [root@localhost ~]# ps -ef|grep httpd
    2. apache    7453 20907  0 Aug14 ?        00:00:01 /usr/sbin/httpd -DFOREGROUND
    3. apache    7454 20907  0 Aug14 ?        00:00:00 /usr/sbin/httpd -DFOREGROUND
    4. apache    7455 20907  0 Aug14 ?        00:00:00 /usr/sbin/httpd -DFOREGROUND
    5. apache    7456 20907  0 Aug14 ?        00:00:00 /usr/sbin/httpd -DFOREGROUND
    6. apache    7457 20907  0 Aug14 ?        00:00:00 /usr/sbin/httpd -DFOREGROUND
    7. root      8753  3688  0 19:10 pts/0    00:00:00 grep --color=auto httpd
    8. root     20907     1  0 Jul21 ?        00:01:39 /usr/sbin/httpd -DFOREGROUND

            好，接下来，再用命令ipcs查看一下新创建的Semaphore总数，也可以使用ipcs -s，只看Semaphore部分：

    1. [root@localhost ~]# ipcs
    2.  
    3. ------ Message Queues --------
    4. key        msqid      owner      perms      used-bytes   messages
    5.  
    6. ------ Shared Memory Segments --------
    7. key        shmid      owner      perms      bytes      nattch     status
    8. 0xe8136391 262144     root       600        1000       0
    9. 0xf513d5ac 1179649    root       600        1000       0
    10. 0x8f13cabc 1409026    root       600        1000       6
    11. 0x00000072 1441795    root       444        1          0
    12.  
    13. ------ Semaphore Arrays --------
    14. key        semid      owner      perms      nsems
    15. 0x00000000 1867776    apache     600        1
    16. 0x00000000 1900545    apache     600        1
    17. 0x00000000 1343490    apache     600        1
    18. 0x00000000 1933315    apache     600        1
    19. 0x00000000 1966084    apache     600        1
    20. 0x00000000 1998853    apache     600        1

            从上图可知，启动httpd之后，Semaphore 总数为6，和进程个数一致。当我们将httpd停止后，再查看一下Semaphore的总数，我所在的测试机器上，总数并未变为0，还是6个。当我再次重启httpd的时候，Semaphore的总数还是6，且内容也没有变化。那么，什么时候它才会自动清除呢，这里留下了疑问，待以后有了解再来补充吧。

            到这里，疑问又来了，既然停止了再重启，Semaphore的内容并未变化，那什么情况下才会出现超过128个Semaphore的情况呢？

            另外，我测试了httpd的2.4.53版本，它的情况又有两处不同：

    1. 进程个数为4；
    2.  Semaphore 的个数为0；

            那么， 是从某个版本开始就不涉及Semaphore的问题了？

    详细内容如下：

    1. [root@localhost mongo]# httpd -v
    2. Server version: Apache/2.4.53 (Unix)
    3. Server built:   May 10 2022 18:55:44
    4. [root@localhost mongo]#
    5. [root@localhost mongo]#
    6. [root@localhost mongo]# systemctl status httpd
    7. ● httpd.service - LSB: start and stop Apache HTTP Server
    8.    Loaded: loaded (/etc/rc.d/init.d/httpd; bad; vendor preset: disabled)
    9.    Active: active (running) since Thu 2022-07-21 18:14:40 CST; 3 weeks 6 days ago
    10.      Docs: man:systemd-sysv-generator(8)
    11.  Main PID: 22906 (httpd)
    12.    CGroup: /system.slice/httpd.service
    13.            ├─ 9671 /usr/sbin/httpd
    14.            ├─ 9672 /usr/sbin/httpd
    15.            ├─ 9673 /usr/sbin/httpd
    16.            └─22906 /usr/sbin/httpd
    17.  
    18. Jul 21 18:14:40 localhost.localdomain systemd[1]: Starting LSB: start and stop Apache HTTP Server...
    19. Jul 21 18:14:40 localhost.localdomain httpd[22899]: Starting httpd: AH00558: httpd: Could not reliably determine the server's fully qualified domain name, using localhost.localdomain. Set the 'ServerN...s this message
    20. Jul 21 18:14:40 localhost.localdomain httpd[22899]: [  OK  ]
    21. Jul 21 18:14:40 localhost.localdomain systemd[1]: Started LSB: start and stop Apache HTTP Server.
    22. Hint: Some lines were ellipsized, use -l to show in full.
    23. [root@localhost mongo]#
    24. [root@localhost mongo]#
    25. [root@localhost mongo]# ipcs
    26.  
    27. ------ Message Queues --------
    28. key        msqid      owner      perms      used-bytes   messages
    29.  
    30. ------ Shared Memory Segments --------
    31. key        shmid      owner      perms      bytes      nattch     status
    32. 0x00000072 0          root       444        1          0
    33.  
    34. ------ Semaphore Arrays --------
    35. key        semid      owner      perms      nsems
    36.  
    37. [root@localhost mongo]#

    疑问越来越多，带着疑问结束本文了，等有这方面的储备了再回来补充吧！

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  • 原文地址：https://blog.csdn.net/lhjlhj123123/article/details/126392267