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Hi, |
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|
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On 2019/10/25 20:14, William Hubbs wrote: |
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> Hey all, |
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> |
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> I have been advised to bring this topic back to the list before taking |
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> any action, so here it is. |
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> |
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> First, I need to clarify what I'm *NOT* talking about. |
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> |
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> This discussion has nothing to do with whether or not you have the |
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> split-usr use flag turned on; all of us officially have that on because |
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> /bin, /lib* and /sbin are directories in the official Gentoo setup. In |
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> other words, I am *not* talking about forcing the /usr merge. |
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> |
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> Unfortunately, the concept of separate usr has gotten wrapped up in the |
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> split-usr use flag and doesn't have to be. For the record, I mean something |
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> very specific when I say "separate usr". I am talking about the situation |
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> where /usr is a mount point separate from /, so in this thread, let's stick |
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> to "separate usr" for that situation. I am *not* even saying that using |
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> separate usr is wrong or unsupported. You can even run separate usr with |
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> split-usr turned off if you would like to do so. |
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> |
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> Now for the use case I want to talk about, and that is using separate |
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> /usr without using an initramfs to boot your system and pre-mount /usr. |
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> |
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> If you do this, many things are broken, and this is why the binary |
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> distros all use an initramfs if you do this. This configuration is also |
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> unsupported officially in Gentoo [1] [2], and it is not shown as the |
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> example setup in our handbook. |
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> |
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> I want to hear from people who have / and /usr on separate partitions |
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> and who are not using an initramfs. |
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> |
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> If you are in this group, I have a very specific question. Why aren't |
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> you using an initramfs? |
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|
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Because until recently it wasn't an issue. So for me the final kicker |
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was still not a separate /usr. For my use case everything except a big |
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warning about md5sum not being available during boot works. This is NOT |
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desktop setup for MOST of my systems. On the few that are I don't |
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generally have things like bluetooth keyboards etc that I need available |
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during early(ish) boot or anything crazy. So the argument that "many |
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things break" may be accurate, but I've yet to find a concrete example |
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that bugs me enough to care. |
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|
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There is basically one thing that I found that broke "out of the box" |
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with a separate /usr - and that's if I have one of those stupid LTE |
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modem things that pretend to be a disk drive/cdrom or something similar |
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until you tell it to switch to network mode. The same thing that, for |
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me, breaks with suspend resume (after resume I have to kill |
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modem_manager, and start it *before* replugging the modem or it simply |
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will not work - another discussion). |
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|
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So frankly, I just don't see the benefit. The reason I've eventually |
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bothered with setting up and creating an initramfs now was because of |
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/lib/firmware which I need available during module load (pre |
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/etc/init.d/localmount) so that firmware is available as soon as amdgpu |
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and i915 loads or else I end up with a borked screen. Only uefi fb |
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compiled into the kernel (required to get hand-over from grub2 ... at |
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least, the only way I could get it to work smoothly). |
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|
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The initramfs we ONLY pull in on systems where it's required (one |
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currently, the machine I'm typing this on). |
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|
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Why do I have /lib/firmware on a separate partition now? Because 512MB |
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for / used to be plenty, and I have MANY history systems out there which |
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is non-trivial to make partitioning changes to (I keep / in a raw |
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partition). Now just /lib/firmware is larger than that. |
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|
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Like William, / and /boot are definite partitions, and I want to keep |
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these small. Everything else is LVM. Most systems have >50% of VG |
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space unallocated because people always overestimate what they really need. |
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|
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Separate partitions means I can set up separate mount options |
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(nosuid,nodev etc ...) |
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|
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Like William, I feel more cogs means more opportunities for breakage. I |
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roll my own vanilla kernel, with one or two of my own patches. I roll |
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my own init script for initramfs. Why - because system bootability is |
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of utmost importance. So I absolutely have to KNOW that it'll work, and |
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when it doesn't that I can walk someone through fixing it over the |
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phone. Never used the default gentoo initramfs. genkernel always pulls |
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in stuff I don't want nor need. Sometimes it's just simpler I guess. |
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But that's the thing - Gentoo gives me CHOICE. Which I don't get from |
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other distributions. These are not the kind of things I like to leave |
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to chance, or in the hands of a continuously changing tool (eg, dracut |
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as mentioned by William). |
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|
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Recently we ran into a bug causing filesystem corruption on /usr/portage |
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(for some reason it was always under /usr/portage). With /usr on a |
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separate partition we could recover that by setting appropriate boot |
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options *remotely*. No need to drive out. Some of these systems were |
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>100km away. |
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|
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So another motivation for separate / and /usr for me is that / is much |
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more read-heavy than /usr, and as such, with the lower write ratio lower |
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risk of corruption. Better ability to recover. |
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|
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As to why not use the initramfs - simple: It's not needed. |
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The only potential advantage in my opinion is if you can build a |
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recovery system in there that's small enough, and contains all |
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conceivable tools required to recover from just about any boot failure. |
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Work-in-progress I guess. |
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|
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I'm not sure that answers your question, and this is one of those |
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debates that can run in circles for hours, days and even weeks. So I |
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hope I at least managed to give you some insight into my thinking and |
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reasoning. |
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|
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Kind Regards, |
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Jaco |