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On Sat, 28 Sep 2013 01:10:14 +0200, Alan McKinnon wrote about Re: |
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[gentoo-user] separate / and /usr to require initramfs 2013-11-01: |
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|
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> On 28/09/2013 00:57, Dale wrote: |
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> > Bruce Hill wrote: |
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> >> On Fri, Sep 27, 2013 at 05:33:02PM -0500, Dale wrote: |
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> >>> I'm hoping that since I use eudev, I don't have to worry about |
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> >>> this. If I do, this could get interesting, again. Dale |
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> >> Do you have /usr separate from / ? |
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> > |
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> > Yep. From my understanding tho, eudev is not supposed to be |
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> > affected by this problem tho. |
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> > |
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> > One reason for this being seperate, I have / and /boot on a regular |
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> > partition and everything else on LVM. Sometimes that /usr gets a |
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> > bit full. It's not so bad after I moved all the portage stuff out |
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> > and put it in /var. Now I have to watch /var too. lol |
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> |
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> |
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> Ask yourself this question: |
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> |
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> Why do you have /usr separate? |
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> |
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> No really, *why exactly*? |
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You write as though you expected the question to be regarded as |
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rhetorical. |
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I can't speak for Dale, but since I have much the same arrangement |
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(with /boot and / on physical partitions and everything else under LVM2 |
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control) I shall write from my perspective. |
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The reason I have /usr separate is so that I can have it striped |
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without needing an initramfs. |
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> One of the very first things you do with /usr at boot time is mount |
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> it, and from then on you use it exactly as if it were always on / |
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> anyway. |
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No. The I/O characteristics of a striped /usr are rather different from |
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those of / on a simple partition. |
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> I'll bet that since you moved all of portage out, your mount |
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> options and fs configs are the same between the two anyway. |
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Again no. My portage volume has different mount options from /usr, as |
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it has nosuid and noexec in force. The portage volume is not striped |
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either, as it does not get as much I/O traffic as /usr. |
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|
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> So what |
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> exactly does a separate /usr get you on a stabd-alone workstation buy |
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> you? |
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|
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It buys me decent performance from elderly PATA hard drives. Striping |
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gives a throughput multiplier on that corner of the DASD farm. |
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This is advantageous because /usr/bin and /usr/lib receive a lot of |
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data traffic running application programs -- much more than /bin |
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and /lib. The /usr/bin directory appears earlier in my PATH than /bin |
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and the majority of application software is loaded without /bin being |
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troubled. The faster the /usr LV can respond, the faster software can |
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load. |
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|
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> I've been looking at this for ages and conclude it buys me |
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> nothing but pain. They don't even change much if /home and /var are |
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> elsewhere, so guage your size right (easy to do) and never need look |
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> at it again. |
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> |
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> Separate /usr for the most part is an ancient artifact from decades |
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> ago. It's useful in edge cases but not in the general case with modern |
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> hardware. So why do people do it? I reckon it's inertia and nothign |
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> more. Which is kinda silly as inertia ignores everythign else in the |
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> environment that is changing around you (and *that* is a given). |
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|
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I'm not sure if you're invoking some law of physics here, but inertia |
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does not ignore everything else -- even if it actually offers |
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resistance to change, it does not ignore it. |
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> So unless you have something exotic like /usr mounted off a central |
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> server, or want / on LVM (and your grub doesn't support lvm), you are |
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> going to need an initramfs anyway to get around the circular bootstrap |
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> problem. |
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I am yet to have a circular dependency problem in my bootstrap |
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sequence. Of course, I don't have bluez installed. I also do not have |
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udev or systemd installed. |
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> I say people should make their lives easier and just stick /usr on the |
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> same volume as / and be done with it. It removes a whole lot of |
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> painful scenarios that are going to keep on biting you as the rest of |
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> the world moves on and progresses |
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That then devolves the I/O characteristics of /usr/bin and /usr/lib |
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into those of /bin and /lib, which would make a slow system even slower. |
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-- |
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Regards, |
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|
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Dave [RLU #314465] |
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dwnoon@××××××××.com (David W Noon) |
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