Re: [vcf-midatlantic] computer superstitions
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.
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@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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