The concept of error distance in sysadmin commands

I have recently started thinking about the concept of what I will callthe 'error distance' of sysadmin commands: how much do you have tochange a perfectly normal command in order to do something undesirableor disastrous (instead of just failing with an error)?

(As an example, consider the ZFS command to expand a ZFS pool witha new pair of mirrored disks, which is ' zpool add POOL mirror DEV1DEV2 '. If you accidentally omit the ' mirror ', you will add twounmirrored


Fixing low command error distances

Suppose that you have a command with an unnervingly low error distance , either because a vendor stuck you with it orbecause it's the natural way to structure the command's arguments.The way to fix this is to change the sort of error required to makea mistake, so that you move from a likely change to an unlikely one.

(If you are working with a vendor command, you will need to do thiswith some sort of a cover script or program. If you are working witha


急 起 直 追   項 明 生

轉載自壹週刊
一篇很勵志的訪問,跟大家分享。



月前與謝一起為一對新人尋覓結婚禮物的時候,在homeless看到這隻豬,一度嚷著要買下來,後來覺得新人會不樂,於是作罷。

後來書展,謝來了,送我禮物,回家拆開,便看到這隻豬,還夾了小籤:「只有你這樣的人,才會喜歡這樣

《 黑 夜 之 神 》 系 列 2 之 誰 是 神 ?



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An update to the ZFS excessive prefetching situation

A while back I wrote about how I had discoveredthat ZFS could wind up doing excessive readahead when faced with manystreams of sequential read IO and wind up throwing 90% to 95% ofthe IO that it had done (with terrible consequences for applicationperformance). It's time for an update on that situation.

First, for various reasons we wound up moving to Solaris server machineswith 8 GB of memory (SunFire X2200s instead of X2100s)


最美的中國運動員

看了這麼多天奧運,得出的結論是 楊伊琳 莫屬。

最令人感動的是她不是塗上一“pat”綠色eye shadow就當是化妝。她會均勻地塗上紫色閃粉。

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ap bank fes ’07 DVD Box Set

其實在此Blog都介紹過一次,但實在太喜歡,加上相信今天看見的DVD Box Set應該數量有限,所以想及早通知各位Blog友。

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Another problem with SSL identities

On top of SSL's general issue there is apractical problem with how SSL information is presented in browsers, onethat makes it very difficult for anyone except very technical people toactually meaningfully verify who a SSL certificate is issued to.

The issue is simple: browsers normally only show you the name of theorganization that the SSL certificate is issued to. But organizationnames are not unique , especially not across the entire world, whichmeans that just the organization name alone tells people less than theythink it does.


Table Manner

With all due respect to the world class table tennis player Wang Nan, she had wonderful performance in women's singles table tennis Olympic game last night.

Did you say she lost her Olympic gold medal? Did she?

If you ask me, I would rather say Wang did well to win a silver. Yes, she won the silver medal with her signature smiles. She cracked a big smile, occasionally sticking out her tongue, even after losing points. The point is not that she wins or loses; her