Confused about Centos 7 Boot selection

[BGood]

I recently installed Centos 7.4 on a development PC and am confused about the 3 different boot options I am offered upon powering up the computer (see screenshot below).

Centos boot.jpg (110.93 KiB) Viewed 2074 times

From the command line (grep '^menuentry' /boot/grub2/grub.cfg) the boot options are listed as follows:

[1] menuentry 'CentOS Linux (3.10.0-693.2.2.el7.x86_64) 7 (Core)' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.10.0-693.2.2.el7.x86_64-advanced-a7603cdc-8932-4d33-9d91-6a2bc93ebede' {
[2] menuentry 'CentOS Linux (3.10.0-693.el7.x86_64) 7 (Core)' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.10.0-693.el7.x86_64-advanced-a7603cdc-8932-4d33-9d91-6a2bc93ebede' {
[3] menuentry 'CentOS Linux (0-rescue-2acdaecad1d641faab8b7e6e4ad759f3) 7 (Core)' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-0-rescue-2acdaecad1d641faab8b7e6e4ad759f3-advanced-a7603cdc-8932-4d33-9d91-6a2bc93ebede' {

On occasion I have restored the Linux partitions from backup images and wonder if Boot options 1 and 2 may have been inadvertently created without erasing previous contents. Based on inspection of portions of the file system, Booters 1 and 2 appear to include the same disk contents. Is it safe to delete #1 or #2 and which should I use? Is a rescue booter #3 automatically created?

Thanks for any guidance!

[desertcat]

I recently installed Centos 7.4 on a development PC and am confused about the 3 different boot options I am offered upon powering up the computer (see screenshot below).

Centos boot.jpg

From the command line (grep '^menuentry' /boot/grub2/grub.cfg) the boot options are listed as follows:

[1] menuentry 'CentOS Linux (3.10.0-693.2.2.el7.x86_64) 7 (Core)' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.10.0-693.2.2.el7.x86_64-advanced-a7603cdc-8932-4d33-9d91-6a2bc93ebede' {
[2] menuentry 'CentOS Linux (3.10.0-693.el7.x86_64) 7 (Core)' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-3.10.0-693.el7.x86_64-advanced-a7603cdc-8932-4d33-9d91-6a2bc93ebede' {
[3] menuentry 'CentOS Linux (0-rescue-2acdaecad1d641faab8b7e6e4ad759f3) 7 (Core)' --class centos --class gnu-linux --class gnu --class os --unrestricted $menuentry_id_option 'gnulinux-0-rescue-2acdaecad1d641faab8b7e6e4ad759f3-advanced-a7603cdc-8932-4d33-9d91-6a2bc93ebede' {

On occasion I have restored the Linux partitions from backup images and wonder if Boot options 1 and 2 may have been inadvertently created without erasing previous contents. Based on inspection of portions of the file system, Booters 1 and 2 appear to include the same disk contents. Is it safe to delete #1 or #2 and which should I use? Is a rescue booter #3 automatically created?

Thanks for any guidance!

The simple answer to your questions is NO!!, NO!!, and NO!!!! Those are the kernels, with 3.10.0-693.2.2.el7.x86_64 being the current kernel. If you delete those you are so hosed -- TOAST!! Yes you could create a new menu, but why do that?!? If the menu starts eating up your partition then simply *COPY* the old kernels to a backup space and leave the latest two plus the Rescue kernel in place, just in case you manage to hose yourself.

[BGood]

Thanks for the timely response before hosing myself in the interest of misguided neatness.

[TrevorH]

Kernels are always installed in parallel, up to the number listed in the installonly_limit= parameter in /etc/yum.conf so thatyou can choose an older one in the even that the most recently installed one fails to boot. You can control the number by adjusting that parameter or let it default to 5. If you know that the most recent one works ok for you and you are 100% sure then you can remove older ones - the best way is to run package-cleanup --oldkernels --count 2 (or however many you want) and it will remove the oldest ones and leave 2 behind.