how to capture the latest kernel version from grub.conf

Question

How can I capture the latest kernel version from grub.conf ( in case default=0)?

For example the latest kernel from the file is 2.6.18-409.el5

 #          all kernel and initrd paths are relative to /boot/, eg.
 #          root (hd0,0)
 #          kernel /vmlinuz-version ro root=/dev/rootvg/slash
 #          initrd /initrd-version.img

#boot=/dev/cciss/c0d0
default=0
timeout=5
#splashimage=(hd0,0)/grub/splash.xpm.gz
#hiddenmenu
title Red Hat Enterprise Linux Server (2.6.18-409.el5)
    root (hd0,0)
    kernel /vmlinuz-2.6.18-409.el5 ro root=/dev/rootvg/slash
    initrd /initrd-2.6.18-409.el5.img

I tried this:

  grep kernel /etc/grub.conf | grep -v "#" |sed s'/-/ /' | head -1 | awk '{print $3}'
  2.6.18-409.el5

but I feel this approach isn't reliable and doesn't handle some cases .

What is the right approach to get the latest kernel only from `grub.conf``.

Answer 1

The approach is specific to the grub version, note that for grub 2+ then kernel has been replaced by linux, so this approach takes that into account

awk '/\/vmlinuz{kernel[$2]}
     END{
     asorti(kernel);
     latest=kernel[length(kernel)];
     print "Latest kernel : ",gensub(/\/vmlinuz-([[:digit:].-]*[[:digit:]]).*$/,"\\1","1",latest)}
    ' /boot/grub/grub.cfg

Sample Output

Latest kernel :  3.13.0-86

---

^{Note: Requires [ gnu-awk ]}