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On Tue, Aug 20, 2013 at 2:44 AM, Helmut Jarausch |
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<jarausch@××××××××××××××××.de> wrote: |
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> On 08/19/2013 04:55:29 PM, Mike Gilbert wrote: |
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>> |
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>> On Mon, Aug 19, 2013 at 5:58 AM, Helmut Jarausch |
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>> <jarausch@××××××××××××××××.de> wrote: |
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>> > Hi, |
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>> > |
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>> > what binaries and libraries have to be put into an initramfs for a |
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>> > system |
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>> > booting with init=/usr/lib/systemd/systemd ? |
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>> > (I am building the initramsfs myself) |
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>> > |
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>> |
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>> You need to get your root filesystem and /usr mounted. Just keep that |
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>> goal in mind and start adding files to support it. |
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>> |
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>> There doesn't need to be anything systemd-specific. |
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>> |
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> |
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> I am not sure about "timing". |
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> |
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> Initially the kernel has only the "mini" /usr partition contained within the |
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> initramfs. |
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> Then it switches to "real root" and only then it tries to mount the "real" |
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> /usr partition. |
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> Does this all happen before the kernel hands control over to the init |
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> process (i.e. systemd) ? |
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> |
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|
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Here's the essence of what you need to accomplish (skip step 2 if you |
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don't have a separate /usr filesystem): |
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|
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1. Mount the "real" root filesystem, which we will call /realroot. |
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2. Mount the /usr filesystem at /realroot/usr. |
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3. Pivot /realroot onto / and exec /usr/lib/systemd/systemd. |
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|
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Step 3 is generally accomplished by a line like this: |
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|
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exec switch_root /realroot /usr/bin/systemd/systemd "$@" |
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|
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If you want to be able to switch inits at boot time, you will need to |
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parse the kernel command line from /proc/cmdline. |
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