Will make modules_install replace old kernel modules?

[Valdis.Kletnieks at vt.edu]

On Thu, 28 May 2015 11:26:02 +0800, Gao Peng said:
>
> I am not sure if I boot from the old kernel,will the old kernel load the
> new-installed modules or keep it's own modules.

If you did it properly, then you should have 2 kernels, each with a
distinct value for uname -r, and 2 directories under /lib/modules, one
for each kernel.  Each kernel then proceeds to load modules from
/lib/modules/`uname -r`.

So if you have a 3.19.0 kernel, and a 4.0.1 kernel, they'll both be
sitting in /boot (each with its own initramfs, probably), and
the 3.19.0 will load from /lib/modules/3.19.0 and the 4.0.1 will load
from /lib/modules/4.0.1

And, of course, you hopefully have grub/grub2/whatever configured to allow
you to select a kernel by having multiple definition stanzas, one per
kernel...

Extreme example (I keep a *lot* of kernels around because I keep breaking them):

[~] ls /boot/vmlinuz-[34]*    
/boot/vmlinuz-3.17.0-0.rc6.git2.1.fc22.x86_64  /boot/vmlinuz-4.0.0-rc3-next-20150310-dirty
/boot/vmlinuz-3.18.0-0.rc3.git0.1.fc22.x86_64  /boot/vmlinuz-4.0.0-rc5-next-20150324
/boot/vmlinuz-3.19.0-0.rc3.git2.1.fc22.x86_64  /boot/vmlinuz-4.0.0-rc6-next-20150331
/boot/vmlinuz-4.0.0-next-20150421              /boot/vmlinuz-4.1.0-rc1-next-20150428
/boot/vmlinuz-4.0.0-rc1-next-20150224          /boot/vmlinuz-4.1.0-rc2-next-20150506
/boot/vmlinuz-4.0.0-rc1-next-20150226-dirty    /boot/vmlinuz-4.1.0-rc4-next-20150521
/boot/vmlinuz-4.0.0-rc1-next-20150303-dirty    /boot/vmlinuz-4.1.0-rc5-next-20150526
/boot/vmlinuz-4.0.0-rc2-next-20150306-dirty
[~] ls /boot/initramfs-[34]*
/boot/initramfs-3.17.0-0.rc6.git2.1.fc22.x86_64.img  /boot/initramfs-4.0.0-rc3-next-20150310-dirty.img
/boot/initramfs-3.18.0-0.rc3.git0.1.fc22.x86_64.img  /boot/initramfs-4.0.0-rc5-next-20150324.img
/boot/initramfs-3.19.0-0.rc3.git2.1.fc22.x86_64.img  /boot/initramfs-4.0.0-rc6-next-20150331.img
/boot/initramfs-4.0.0-next-20150421.img              /boot/initramfs-4.1.0-rc1-next-20150428.img
/boot/initramfs-4.0.0-rc1-next-20150224.img          /boot/initramfs-4.1.0-rc2-next-20150506.img
/boot/initramfs-4.0.0-rc1-next-20150226-dirty.img    /boot/initramfs-4.1.0-rc4-next-20150521.img
/boot/initramfs-4.0.0-rc1-next-20150303-dirty.img    /boot/initramfs-4.1.0-rc5-next-20150526.img
/boot/initramfs-4.0.0-rc2-next-20150306-dirty.img
[~] ls /lib/modules
3.17.0-0.rc6.git2.1.fc22.x86_64  4.0.0-rc1-next-20150224        4.0.0-rc3-next-20150310-dirty  4.1.0-rc2-next-20150506
3.18.0-0.rc3.git0.1.fc22.x86_64  4.0.0-rc1-next-20150226-dirty  4.0.0-rc5-next-20150324        4.1.0-rc4-next-20150521
3.19.0-0.rc3.git2.1.fc22.x86_64  4.0.0-rc1-next-20150303-dirty  4.0.0-rc6-next-20150331        4.1.0-rc5-next-20150526
4.0.0-next-20150421              4.0.0-rc2-next-20150306-dirty  4.1.0-rc1-next-20150428

Hope that helps it make sense...