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Old 11-30-2005, 12:02 PM   #1
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Registered: Nov 2005
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Rebooting And Unmounting

On some Linux faq i read that you should NOT do a hard reboot [[ reset button ]] if you
have drives mounted. Does Linux somehow lock drives so they can be damaged upon
hard reboot? Under good ol DOS your hard drive is ALWAYS mounted [[my understanding]]
and i often did RESET without worry......
Old 11-30-2005, 12:35 PM   #2
Registered: Aug 2005
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The problem relates more to 32 bit OS's caching disk writes. Dos didn't do any disk caching, so hitting reset wouldn't corrupt anything (unless you were in a rare long disk write process at the time of reset). Linux, Windows, Most Unix's, and other 32 bit multitasking OS's utilize disk caching techniques to speed up user performance on a system by writing to the disk between user app cycles. The chances of corrupting a disk by hitting reset in Linux, thus, are far greater than in Dos, but are not a definite result. For example, hitting reset on a system that is sitting idle, with virutally no cpu load, and no swap file usage, has a lower chance of corruption than a system that is under a greater load, and writing to disk constantly.

To better help fight against disk corruption, most file systems implemented in Linux set a flag on the partition when mounting it r/w, so that if a reset does occur, it will automatically check to make sure nothing got clobbered. Using a journaling file system (ext3, JFS, Reiserfs, etc) makes the system more stable, as it can store a disk write command in a journal, then mark the journal entry as completed once the actual write has finished. When rebooting a running system with a journaling filesystem, the system detects a dirty partition, then looks through the journal for incomplete writes, backing out any changes that were incomplete.

Hope this information was helpful.
Old 11-30-2005, 12:53 PM   #3
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Very good answer. Thank you muchly.
Old 11-30-2005, 01:25 PM   #4
Registered: May 2004
Distribution: Slackware / GoboLinux / LFS / VoidLinux
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I dont have such a good reply as my knowledge is limited, but I can tell you of my experience.

I often did and still do hard resets, and I sometimes had a problem, once a BIOS problem which had to do with memory (it failed to boot up after i did this).

I think if you have only one PC and this must be working, dont make hard reboots, the time is worth to make slow reboots
But otherwise, its extremely safe to hard reboot, especially if you dont care about data loss anyway (having external hdd, or second internal IDE hdds for instance)


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