[PATCH][retry-2] init: Introduce rootdir bootparm to select which dir to sys_chroot - Kernel

This is a discussion on [PATCH][retry-2] init: Introduce rootdir bootparm to select which dir to sys_chroot - Kernel ; Second try; this time with a doc-update, and the ability to remount normally. Tested against 2.6.23. --- This patch introduces a rootdir kernel boot parameter, which specifies the path to the kernel sys_chroot boot dir. This is useful for systems ...

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Thread: [PATCH][retry-2] init: Introduce rootdir bootparm to select which dir to sys_chroot

  1. [PATCH][retry-2] init: Introduce rootdir bootparm to select which dir to sys_chroot


    Second try; this time with a doc-update, and the ability to remount normally.

    Tested against 2.6.23.

    ---

    This patch introduces a rootdir kernel boot parameter, which specifies the
    path to the kernel sys_chroot boot dir.

    This is useful for systems that have more than one distribution installed on
    the same fs/partition.


    Cc: H. Peter Anvin
    Cc: Andrew Morton
    Signed-off-by: Al Boldi

    ---

    --- a/Documentation/kernel-parameters.txt
    +++ b/Documentation/kernel-parameters.txt
    @@ -1506,6 +1506,10 @@ and is between 256 and 4096 characters.
    Useful for devices that are detected asynchronously
    (e.g. USB and MMC devices).

    + rootdir= [KNL] Set root dir to chroot to on bootup.
    + Useful for systems that have more than one distribution
    + installed on the same filesystem.
    +
    rw [KNL] Mount root device read-write on boot

    S [KNL] Run init in single mode
    --- a/init/do_mounts.c
    +++ b/init/do_mounts.c
    @@ -252,6 +252,16 @@ __setup("rootflags=", root_data_setup);
    __setup("rootfstype=", fs_names_setup);
    __setup("rootdelay=", root_delay_setup);

    +static char __initdata root_dir[128];
    +static int __init root_dir_setup(char *str)
    +{
    + strcpy(root_dir, "./");
    + strlcat(root_dir, str, sizeof(root_dir));
    + return 1;
    +}
    +
    +__setup("rootdir=", root_dir_setup);
    +
    static void __init get_fs_names(char *page)
    {
    char *s = page;
    @@ -469,6 +479,12 @@ void __init prepare_namespace(void)
    mount_root();
    out:
    sys_mount(".", "/", NULL, MS_MOVE, NULL);
    +
    + if (root_dir) {
    + sys_mount(root_dir, root_dir, NULL, MS_BIND, NULL);
    + sys_chdir(root_dir);
    + }
    +
    sys_chroot(".");
    security_sb_post_mountroot();
    }

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  2. Re: [PATCH][retry-2] init: Introduce rootdir bootparm to select which dir to sys_chroot

    On Sun, 18 Nov 2007 20:09:19 +0300
    Al Boldi wrote:

    >
    > Second try; this time with a doc-update, and the ability to remount
    > normally.



    Hi,

    to be honest, this is something that really should be done in the
    initramfs image; we should strive to keep the more complex bootup
    scenarios there and not inside the kernel bootup code...

    Greetings,
    Arjan van de Ven

    --
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  3. Re: [PATCH][retry-2] init: Introduce rootdir bootparm to select which dir to sys_chroot

    Arjan van de Ven wrote:
    > to be honest, this is something that really should be done in the
    > initramfs image; we should strive to keep the more complex bootup
    > scenarios there and not inside the kernel bootup code...


    Agreed, but this is neither complex nor is it a scenario.

    This is a shortcut. And, IMHO, a clean one.


    Thanks!

    --
    Al

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