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Council members, |
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As we all know, the way most linux distros support having /usr on a |
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separate file system from / is via an initramfs. One of these can be |
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built easily in gentoo with dracut, genkernel, or you can build one |
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manually [1]. |
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|
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In april 2012, the council voted that "separate /usr is a supported |
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configuration". According to a number of people at the time and since |
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then, the intent was to mandate that maintainers must support separate /usr |
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configurations without an initramfs. |
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|
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This is the reason for the "sep-usr" use flag in busybox. This use flag |
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is a Gentoo-specific option that drops the busybox static binary in / with a |
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different name (ginit). Then you add init=/ginit on your kernel command |
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line with your boot loader configuration to run this binary which just |
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mounts / and /usr and starts the real init. |
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|
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The council never really took a position on how separate /usr is |
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supported, so there are people who use separate /usr with neither of |
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these options and still expect this configuration to work. |
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|
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There are significant advantages if we do not require maintainers to |
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support the use of separate /usr configurations without an early boot |
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mechanism like an initramfs or the sep-usr use flag on busybox. |
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|
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First, we will not have to worry any more about making sure all of the |
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libraries needed by binaries in /{bin,sbin} are in /lib*. Also, we will |
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not have to be concerned about programs on / trying to read data from |
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/usr/share in early boot. |
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|
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Also, the support for separate /usr setups without any kind of early |
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boot mechanism is going to become more complex over time due to the |
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evolution of modern software. Our QA lead has some blog posts on the |
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separate /usr issue and the boot process which discuss these issues in |
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more detail [2] [3]. Another thing to consider is FHS 3 [4]. The division |
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between / and /usr is becoming blurred because any combination of |
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actual directories and symlinks are allowed in /. |
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|
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Because of this information, I propose that we vote not to |
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require maintainers to support separate /usr configurations without an |
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initramfs or some other early boot mechanism. |
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|
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William |
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|
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[1] http://www.gentoo.org/doc/en/initramfs-guide.xml |
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[2] https://blog.flameeyes.eu/2012/12/my-take-on-the-separate-usr-issue |
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[3] https://blog.flameeyes.eu/2013/01/the-boot-process |
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[4] http://www.linuxbase.org/betaspecs/fhs/fhs.html |
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