Kernel & initrd
Kernel
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What is a Linux Kernel?
The Linux kernel is the core software that acts as an interface between the hardware and various software applications running on your system.
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Check kernel version
uname -rAfter installing a new kernel version, a server reboot is required.
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Which file in /boot is the kernel?
Typically, the kernel file itself (located within /boot) is prefaced with 'vmlinuz', for example:
vmlinuz-5.15.0-106-generic
Working on Linux systems, you may see systems with various kernels installed.
To check which kernel is currently being treated as the primary one (which will be loaded on boot), you can check the symlinks (in /boot), as below:
vmlinuz -> vmlinuz-5.15.0-107-generic
vmlinuz.old -> vmlinuz-5.15.0-106-generic
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initrd
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What is initrd?
initrd (initialisation RAM disk) is essentially a set of instructions used to load the kernel. initrd is stored temporarily in system memory whilst the kernel is loaded.
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Which file in /boot is initrd?
The initrd file will be prefaced with just that - initrd:
initrd.img-5.15.0-106-generic
To check which initrd file is currently being treated as the primary one (which will be loaded on boot), you can check the symlinks (in /boot), as below:
initrd.img -> initrd.img-5.15.0-107-generic
initrd.img.old -> initrd.img-5.15.0-106-generic
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