Extract initramfs on RHEL/CentOS 7

By | 16/06/2016

The initramfs is a compress cpio archive. Use the dracut skipcpio tool to extract the compress cpio file then gunzip that and finally extract the archive using cpio. Luckily we can chain these commands together.

# mkdir /tmp/initramfs
# cd /tmp/initramfs
# /usr/lib/dracut/skipcpio /boot/initramfs-3.10.0-327.18.2.el7.x86_64.img | gunzip -c | cpio -dcim
# ls -l
total 12
lrwxrwxrwx. 1 root root 7 Jun 16 09:14 bin -> usr/bin
drwxr-xr-x. 2 root root 42 Jun 16 09:14 dev
-rw-r--r--. 1 root root 2 Jun 7 16:43 early_cpio
drwxr-xr-x. 13 root root 4096 Jun 16 09:14 etc
lrwxrwxrwx. 1 root root 23 Jun 16 09:14 init -> usr/lib/systemd/systemd
-rw-r--r--. 1 root root 0 Jun 16 09:11 initramfs.cpio
drwxr-xr-x. 3 root root 16 Jun 16 09:07 kernel
lrwxrwxrwx. 1 root root 7 Jun 16 09:14 lib -> usr/lib
lrwxrwxrwx. 1 root root 9 Jun 16 09:14 lib64 -> usr/lib64
drwxr-xr-x. 2 root root 6 Jun 7 16:43 proc
drwxr-xr-x. 2 root root 6 Jun 7 16:43 root
drwxr-xr-x. 2 root root 6 Jun 7 16:43 run
lrwxrwxrwx. 1 root root 8 Jun 16 09:14 sbin -> usr/sbin
-rwxr-xr-x. 1 root root 3041 Dec 4 2015 shutdown
drwxr-xr-x. 2 root root 6 Jun 7 16:43 sys
drwxr-xr-x. 2 root root 6 Jun 7 16:43 sysroot
drwxr-xr-x. 2 root root 6 Jun 7 16:43 tmp
drwxr-xr-x. 7 root root 61 Jun 16 09:14 usr
drwxr-xr-x. 3 root root 37 Jun 16 09:14 var

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