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I am quite new to Linux administration so I am having trouble understanding yum update and grub boot list.

I recently did a yum update on an old CentOS machine. Everything is good except there is multiple boot options appear in grub boot list and I wonder why? I managed to do a Google search and figured I can manually configure the boot order in /etc/grub.conf.

  1. Does it mean I now have multiple OS installed?
  2. Will my grub list grow if I do future yum update?
  3. Do I need to clean up old item from the list?

Thanks.

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2 Answers 2

up vote 1 down vote accepted
  1. No, just other versions (usually older) of the kernel, as noted above.

  2. Yes, each time you update the kernel, you will get a new entry.

  3. No. Probably the easiest way if you want to would be to go to /boot and remove the older kernels and related files (they will have the same string in the middle, such as 2.6.9-42). I would at a minimum keep the current and previous version (ie two known good configs), just in case. But frankly, who cares? Not much space(14MB for the example bellow), and you can just ignore the old stuff, as it's down the bottom of the screen.

some_hostname Sun Jan 03 19:17:58 /boot
root > ls -1t
grub                             <- boot loader config files
initrd-2.6.9-78.0.13.EL.img          <- the 2.6.9-78 related files
initrd-2.6.9-78.0.13.ELsmp.img       <- for both smp (multi core/thread)
symvers-2.6.9-78.0.13.ELsmp.gz       <- and uni processor
config-2.6.9-78.0.13.ELsmp           <-
System.map-2.6.9-78.0.13.ELsmp       <-
vmlinuz-2.6.9-78.0.13.ELsmp          <-
symvers-2.6.9-78.0.13.EL.gz          <-
config-2.6.9-78.0.13.EL              <-
System.map-2.6.9-78.0.13.EL          <-
vmlinuz-2.6.9-78.0.13.EL             <-
initrd-2.6.9-42.ELsmp.img
initrd-2.6.9-42.EL.img
lost+found
config-2.6.9-42.ELsmp
System.map-2.6.9-42.ELsmp
vmlinuz-2.6.9-42.ELsmp
config-2.6.9-42.EL
System.map-2.6.9-42.EL
vmlinuz-2.6.9-42.EL
message
message.ja
some_hostname Sun Jan 03 19:18:05 /boot
root > 

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If you install a new kernel through yum it will appear in your boot list. I think yum takes the current one, makes it a second entry, then makes the new kernel the default/first entry. This lets you boot the old kernel if you need after updating and having a problem.

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