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| <div class="CHAPTER"> | | <div class="CHAPTER"> |
− | =Process startup, supervision and shutdown= | + | ==Process startup, supervision and shutdown== |
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| <div class="SECT1"> | | <div class="SECT1"> |
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− | ==Process startup== | + | ===Process startup=== |
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| In typical Linux systems, services (processes) are started at boot time through a mechanism such as <span class="emphasis">''System V init''</span>. When the system administrator needs to change the settings, they modify the configuration files and then restart the service or notify the process that it needs to re-read the configuration. | | In typical Linux systems, services (processes) are started at boot time through a mechanism such as <span class="emphasis">''System V init''</span>. When the system administrator needs to change the settings, they modify the configuration files and then restart the service or notify the process that it needs to re-read the configuration. |
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− | ==Process supervision: runit (and supervise)== | + | ===Process supervision: runit (and supervise)=== |
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| The SME Server addresses these issues by running processes under the '''runit''' process supervision environment, which: | | The SME Server addresses these issues by running processes under the '''runit''' process supervision environment, which: |
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− | ===The runit process tree=== | + | ====The runit process tree==== |
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| When a Linux system boots, it starts the '''init''' process, which then starts all other processes. When '''init''' enters "run-level 7", it starts '''/etc/runit/2''' from an entry in <tt class="FILENAME">/etc/inittab</tt>. | | When a Linux system boots, it starts the '''init''' process, which then starts all other processes. When '''init''' enters "run-level 7", it starts '''/etc/runit/2''' from an entry in <tt class="FILENAME">/etc/inittab</tt>. |
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− | ===Run-level 7 and the e-smith-service wrapper=== | + | ====Run-level 7 and the e-smith-service wrapper==== |
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| The SME Server runs in the normally unused run-level 7. This ensures that the only software running on the SME Server is software that we have chosen to run, and it is started and stopped in a consistent way. If we need to replace a standard startup script with one which runs the process under supervise, we can do so <span class="emphasis">''without modifying the original package''</span>. | | The SME Server runs in the normally unused run-level 7. This ensures that the only software running on the SME Server is software that we have chosen to run, and it is started and stopped in a consistent way. If we need to replace a standard startup script with one which runs the process under supervise, we can do so <span class="emphasis">''without modifying the original package''</span>. |