====== Boot ======

=== Grub ===

  * Grub 2 - Setting default entry <code bash>
Open /etc/default/grub and ensure this line exists:
GRUB_DEFAULT=saved

Apply the change to grub.cfg by running:
# grub2-mkconfig -o /boot/grub2/grub.cfg

Now list all possible menu entries
# grep ^menuentry /boot/grub2/grub.cfg | cut -d "'" -f2

Now set the desired default menu entry
# grub2-set-default <menu entry title>

Verify the default menu entry
# grub2-editenv list
</code>

grubby
<code>
# grubby --default-kernel
# grubby --set-default=/boot/vmlinuz-3.10.0-514.el7.x86_64 
</code>
=== Systemd ===
  * Enable rc-local in OL7<code bash>
cat >> /usr/lib/systemd/system/rc-local.service <<EOF

[Install]
WantedBy=multi-user.target
EOF
chmod +x /etc/rc.d/rc.local
systemctl enable rc-local.service
systemctl start rc-local.service
systemctl status rc-local.service

echo "systemctl restart network.service" >> /etc/rc.d/rc.local
</code>

=== Initramfs ===
<code>
# extract initramfs in RHEL7/Centos7
/usr/lib/dracut/skipcpio initramfs-3.10.0-229.el7.x86_64.img | zcat | cpio -idv
</code>

=== Debug ===
<code>
kernel cmd line: debug initcall_debug systemd.log_target=console systemd.journald.forward_to_console=1
serial console in grub:
serial --unit=0 --speed=115200
terminal --timeout=10 console serial
kernel cmd line: console=tty1 console=ttyS0,115200n8
</code>