# Confirm current user privileges
whoami  # Expected output: root

# Confirm the system distribution identifier (tl3 or tl4)
cat /etc/rpm/macros.dist 2>/dev/null || rpm --eval '%{dist}'
# Expected output: .tl3 or .tl4

# Confirm the /boot partition space (at least 300 MB)
df -h /boot
# Expected output: The Avail column is no less than 300M.

# Back up the GRUB configuration (perform this step before modifying the default boot kernel)
cp /boot/grub2/grub.cfg /boot/grub2/grub.cfg.bak.$(date +%Y%m%d)

# View the running kernel version
uname -r
# Expected output example: 5.4.241-24.0017.14.tl3.x86_64

# View all installed kernels
rpm -qa | grep kernel | sort
# Expected output: List all installed kernel RPM packages

# View distribution information (determine whether it is .tl3 or .tl4)
cat /etc/rpm/macros.dist 2>/dev/null || rpm --eval '%{dist}'
# Expected output: %dist .tl3 or %dist .tl4 (tl4 can be replaced by rpm --eval)

# View available kernel versions
dnf list kernel* --showduplicates | head -20
# Expected output: List all available kernel version packages

# Upgrade to the latest kernel
dnf update kernel -y
# Expected output: The installation/upgrade process is displayed, and "Complete!" is prompted at the end.

# Or install a specific version (replace <version_number> with the actual version)
dnf install kernel-<version_number> -y

# Restart after the upgrade is complete (a restart will cause service interruption, so make sure a maintenance window has been scheduled before proceeding)
reboot

# View the current default kernel booted by GRUB
grubby --default-kernel
# Expected output: /boot/vmlinuz-5.4.241-24.0017.14.tl3.x86_64

# List all installed kernel images
ls /boot/vmlinuz-*
# Expected output:
# /boot/vmlinuz-5.4.119-19.0009.13.tl3.x86_64
# /boot/vmlinuz-5.4.241-24.0017.14.tl3.x86_64

# Or view via rpm
rpm -qa | grep kernel | sort

# Set the specified kernel as the default boot kernel (replace <kernel-path> with the actual kernel path)
grubby --set-default /boot/vmlinuz-<kernel-version>
# Example: grubby --set-default /boot/vmlinuz-5.4.241-24.0017.14.tl3.x86_64
# Expected output: The default is set to a nonzero entry. Success!

# Restart the system (a restart will cause service interruption, so make sure a maintenance window has been scheduled before proceeding)
reboot

# After restart, confirm that the currently running kernel is the default kernel you set
uname -r
# Expected output: 5.4.241-24.0017.14.tl3.x86_64 (consistent with the default kernel you set)

# Confirm the default boot kernel configuration again
grubby --default-kernel
# Expected output: /boot/vmlinuz-5.4.241-24.0017.14.tl3.x86_64

# Attempting a regular installation of a lower kernel version will result in an error:
# "package xxx (which is newer than xxx) is already installed"
# Use --force --nodeps to force the installation
rpm -ivh --force --nodeps kernel-5.4.119-19.0009.13.tl3.x86_64.rpm
# Expected output: The installation progress is displayed, and "##### [100%]" is shown at the end.

# View all installed kernels
rpm -qa | grep kernel | sort
# Expected output: List all installed kernel RPM packages

# Remove the specified old kernel (make sure not to remove the currently running kernel)
rpm -e kernel-5.4.119-19.0009.13.tl3.x86_64
# Expected output: A message indicating that the uninstallation is complete.

# Check /boot usage
df -h /boot
# Expected output: Available space has increased.

# 1. Confirm that the new kernel is running.
uname -r
# Expected output: 5.4.241-24.0017.14.tl3.x86_64 (consistent with the target installation version)

# 2. Confirm that the system starts up normally.
systemctl --failed
# Expected output: 0 loaded units listed (no failed services)

# 3. Confirm the kernel boot order.
grubby --default-kernel
# Expected output: /boot/vmlinuz-5.4.241-24.0017.14.tl3.x86_64

# 1. Confirm that the new kernel is installed.
rpm -qa | grep kernel | sort

# 2. View the current default boot kernel.
grubby --default-kernel

# 3. Set the new kernel as the default boot kernel.
grubby --set-default /boot/vmlinuz-<kernel-version>
# Example: grubby --set-default /boot/vmlinuz-5.4.241-24.0017.14.tl3.x86_64

# 4. Restart and verify (a restart will cause service interruption, so perform this operation within a maintenance window)
reboot
uname -r

# To install a lower version (downgrade), use --force --nodeps to force the installation.
rpm -ivh --force --nodeps kernel-<version>.tl3.x86_64.rpm

# To upgrade or replace with a higher version, use the -U parameter.
rpm -Uvh kernel-<version>.tl3.x86_64.rpm

# Install all three packages (replace <version_number> with the actual version)
rpm -ivh kernel-<version>.tl3.x86_64.rpm \\
        kernel-core-<version>.tl3.x86_64.rpm \\
        kernel-modules-<version>.tl3.x86_64.rpm

# Or use dnf to handle dependencies automatically.
dnf install kernel-<version_number> -y

# 1. Check the available space in /boot.
df -h /boot

# 2. Clean up old kernels (keep the latest 2)
package-cleanup --oldkernels --count=2

# 3. Or manually remove unused old kernels (first confirm the currently running kernel)
uname -r  # Record the current kernel. Do not delete it.
rpm -e kernel-<old_version>.tl3.x86_64

# 4. If space is still insufficient after cleanup, expand the partition containing /boot. Proceed with caution and back up data before the operation.
# On a CVM, /boot is typically located in the root partition. You can first expand the system disk in the console, and then extend the partition and file system:
growpart /dev/vda 1   # Expand the partition (assuming the root partition is /dev/vda1)
xfs_growfs /          # Expand the file system (xfs). For ext4, use resize2fs /dev/vda1.

# 5. Reinstall the target kernel.
rpm -ivh kernel-<version>.tl3.x86_64.rpm