Why no "System Restart Required" message after Amazon Linux kernel update?

Question

I ran sudo yum update on an Amazon Linux instance and it updated the kernel. On other distos I've seen, this causes a message to appear when you login saying System Restart Required. Why don't I see it here?

Last login: Mon Jun  2 17:06:11 2014 from ...

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       _|  (     /   Amazon Linux AMI
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https://aws.amazon.com/amazon-linux-ami/2014.03-release-notes/

[myuser@dev ~]$ uname -a
Linux dev.myhost.com.au 3.4.82-69.112.amzn1.x86_64 #1 SMP Mon Feb 24 16:31:21 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

[myuser@dev ~]$ cd /boot

[myuser@dev boot]$ ls -l 
total 45208
-rw-r--r-- 1 root root    80189 May  6 04:31 config-3.10.38-49.136.amzn1.x86_64
-rw-r--r-- 1 root root    80189 May 14 07:38 config-3.10.40-50.136.amzn1.x86_64
-rw-r--r-- 1 root root    70178 Feb 25 03:36 config-3.4.82-69.112.amzn1.x86_64
drwxr-xr-x 2 root root     4096 Jun  2 17:07 grub
-rw------- 1 root root 10203096 May 12 03:58 initramfs-3.10.38-49.136.amzn1.x86_64.img
-rw------- 1 root root 10203665 Jun  2 17:07 initramfs-3.10.40-50.136.amzn1.x86_64.img
-rw------- 1 root root  8777362 Mar  4 23:18 initramfs-3.4.82-69.112.amzn1.x86_64.img
-rw-r--r-- 1 root root   128784 May  6 04:31 symvers-3.10.38-49.136.amzn1.x86_64.gz
-rw-r--r-- 1 root root   128805 May 14 07:38 symvers-3.10.40-50.136.amzn1.x86_64.gz
-rw------- 1 root root  2201080 May  6 04:31 System.map-3.10.38-49.136.amzn1.x86_64
-rw------- 1 root root  2201155 May 14 07:38 System.map-3.10.40-50.136.amzn1.x86_64
-rw------- 1 root root  1727495 Feb 25 03:36 System.map-3.4.82-69.112.amzn1.x86_64
-rwxr-xr-x 1 root root  3657552 May  6 04:31 vmlinuz-3.10.38-49.136.amzn1.x86_64
-rwxr-xr-x 1 root root  3659152 May 14 07:38 vmlinuz-3.10.40-50.136.amzn1.x86_64
-rwxr-xr-x 1 root root  3145488 Feb 25 03:36 vmlinuz-3.4.82-69.112.amzn1.x86_64

[myuser@dev boot]$ cat grub/grub.conf 
# created by imagebuilder
default=0
timeout=1
hiddenmenu

title Amazon Linux 2014.03 (3.10.40-50.136.amzn1.x86_64)
root (hd0)
kernel /boot/vmlinuz-3.10.40-50.136.amzn1.x86_64 root=LABEL=/ console=hvc0 LANG=en_US.UTF-8 KEYTABLE=us
initrd /boot/initramfs-3.10.40-50.136.amzn1.x86_64.img

title Amazon Linux 2014.03 (3.10.38-49.136.amzn1.x86_64)
root (hd0)
kernel /boot/vmlinuz-3.10.38-49.136.amzn1.x86_64 root=LABEL=/ console=hvc0 LANG=en_US.UTF-8 KEYTABLE=us
initrd /boot/initramfs-3.10.38-49.136.amzn1.x86_64.img

title Amazon Linux 2013.09 (3.4.82-69.112.amzn1.x86_64)
root (hd0)
kernel /boot/vmlinuz-3.4.82-69.112.amzn1.x86_64 root=LABEL=/ console=hvc0 LANG=en_US.UTF-8 KEYTABLE=us
initrd /boot/initramfs-3.4.82-69.112.amzn1.x86_64.img

Reboot system and confirm the new kernel is running...

Last login: Thu Jun  5 10:55:30 2014 from ...

       __|  __|_  )
       _|  (     /   Amazon Linux AMI
      ___|\___|___|

https://aws.amazon.com/amazon-linux-ami/2014.03-release-notes/
[myuser@dev ~]$ uname -a
Linux dev.myhost.com.au 3.10.40-50.136.amzn1.x86_64 #1 SMP Tue May 13 21:35:08 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux

Answer 1

That's mainly an Ubuntu thing (and I suppose Debian). It's part of the update-motd system, where there's a bunch of scripts in /etc/update-motd.d that occasionally rewrite the Message Of The Day that gets displayed when you first log in. Here's the Ubuntu wiki page on this

Amazon Linux is derived from Red Hat Enterprise Linux (i.e., you are using "yum" instead of "apt"), and apparently doesn't have a dynamic message of the day system.