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On Friday 28 April 2006 20:04, Phil Sexton <philsexton@×××××××.net> wrote |
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about 'Re: [gentoo-user] When to reboot after updates to the system': |
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> Kevin wrote: |
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> > Hi All- |
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> > |
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> > I've read the portage documentation at |
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> > http://www.gentoo.org/doc/en/index.xml?catid=gentoo and I've searched |
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> > and browsed the gentoo-user mailing list archive, but I have a |
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> > question that I don't see answered anywhere. |
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> > |
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> > It seems to me that it must be true that sometimes, after a system |
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> > upgrade done with: |
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> > |
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> > emerge -uD system |
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> > or |
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> > emerge -uD world |
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> > |
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> > I must reboot the computer for the changes to take effect. |
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> |
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> I reboot if I need to install or change hardware. As far as |
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> updates go, you may have to reboot after compiling a new kernel. |
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> |
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> I think that I may have read somewhere how to change kernels |
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> without rebooting, so you may not even need to reboot for any |
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> software. |
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|
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Theoretically it's possible just by writing to /proc/kmem -- IIRC, that was |
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one of the reasons it was writable: so you could apply (binary) patches |
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against a running kernel. |
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|
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I've never seen any non-malware that does so. There is a GPL'd |
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proof-of-concept rootkit that will hide its existence by |
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modifying /proc/kmem. (The rootkit doesn't actually do anything malicious |
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and you have to have root access to modify /proc/kmem; the rootkit was |
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just showing how to do this trickery without loading a module) |
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|
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There's also the new kexec feature option in mm kernels (and it might have |
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come mainline) that allows the kernel to start another kernel instead of |
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rebooting your hardware. That's basically as bad as a reboot anyway, |
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because all services come down and all users are kicked out -- it is |
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faster though, because you don't go down to the bootloader/BIOS level. |
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|
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I found it (or my hardware) was a little bit buggy. My USB drivers would |
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only work every other kexec. Since I use a USB keyboard, this wasn't a |
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workable solution. |
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|
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-- |
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"If there's one thing we've established over the years, |
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it's that the vast majority of our users don't have the slightest |
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clue what's best for them in terms of package stability." |
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-- Gentoo Developer Ciaran McCreesh |
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