[vcf-midatlantic] computer superstitions

Neil Cherry ncherry at linuxha.com
Fri Oct 25 09:42:09 EDT 2019


On 10/25/19 3:25 AM, Jeffrey Jonas via vcf-midatlantic wrote:
>> You need three sync's for it to work...
>> sync
>> sync
>> sync
>> halt
> 
> I'm unsure there was a halt or shutdown for Unix v6.
> I think one just halted the CPU.
> 
> There's a good reason for three syncs.
> The "sync" command only schedules/initiates the buffer/cache flush.
> The disk writes took time, so typing it 3x on a teletype was a simple way
> to delay the operator enough for the writes to complete before halting
> the system.
> 

That was also true SYSV R2.x and R3.x on the 3B2s. I think shutdown and
halt did the same thing on machines without the soft power off. If it
did have the soft power off the shutdown would also turn off the power
when all the shutdown scripts had been run.

-- 
Linux Home Automation         Neil Cherry       ncherry at linuxha.com
http://www.linuxha.com/                         Main site
http://linuxha.blogspot.com/                    My HA Blog
Author of:    	Linux Smart Homes For Dummies


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