[CentOS] How to update modules in iniramfs fastly

[wuzhouhui]

> -----Original Messages-----
> From: "Steven Tardy" <sjt5atra at gmail.com>
> Sent Time: 2018-02-26 10:48:48 (Monday)
> To: "CentOS mailing list" <centos at centos.org>
> Cc: 
> Subject: Re: [CentOS] How to update modules in iniramfs fastly
> 
> On Sun, Feb 25, 2018 at 8:29 PM wuzhouhui <wuzhouhui14 at mails.ucas.ac.cn>
> wrote:
> 
> > I know dracut can update modules in initramfs, but I think it is too
> > slow. So I'm wondering what is the fastest way to update modules in
> > initramfs of CentOS 7?
> 
> 
> `dracut` calls `mkinitrd` which rebuilds the initrd file. . . you could do
> it manually but that is prone to errors (
> https://access.redhat.com/solutions/24029).
This solution does not work in CentOS 7, because initramfs in CentOS 7 is not
a gzipped cpio:
   [root at bogon a]# file /boot/initramfs-3.10.0-693.el7.x86_64.img 
   /boot/initramfs-3.10.0-693.el7.x86_64.img: ASCII cpio archive (SVR4 with no CRC)
If I use
   zcat /boot/initrd-2.6.18-164.6.1.el5.img | cpio -idmv
to uncompress initramfs, it will report errors:
   [root at bogon a]# zcat /boot/initramfs-3.10.0-693.el7.x86_64.img | cpio -idmv

   gzip: /boot/initramfs-3.10.0-693.el7.x86_64.img: not in gzip format
   cpio: premature end of archive
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