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    Server Migration Center:Resolve the "Not enough space on /boot" error

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    Server Migration Center:Resolve the "Not enough space on /boot" error

    Last Updated:Jun 03, 2026

    Problem description

    The "Not enough space on /boot" error occurs during operating system migration.

    Cause

    The /boot partition requires at least 100 MiB of free space to install the new initramfs and kernel. If the /boot directory has less than 100 MiB available, the migration fails.

    Solution

    Remove unused kernel versions from the /boot directory, including the corresponding initramfs, vmlinuz, and config files. Verify that the system boots correctly after removal.

    1. Connect to the ECS instance as the root user. Connect to a Linux instance by using a password or key.

    2. View the installed kernel versions: 

      rpm -qa | grep kernel

    3. Check the currently running kernel version: 

      uname -r

      Example output: 

      [root@iZbp104w56ovfyfxy9o**** ~]# uname -r
3.10.0-1160.el7.x86_64

    4. Remove unused kernel versions.

      In this example, kernel-3.10.0-514.26.2.el7.x86_64 is removed.

      • If the kernel was installed from an RPM package, run: 

        yum remove kernel-3.10.0-514.26.2.el7.x86_64

      • If the kernel was installed by compiling the source code, run the following commands in sequence: 

        REMOVE_KERNEL=3.10.0-514.26.2.el7.x86_64
grubby --remove-kernel=/boot/vmlinuz-$REMOVE_KERNEL
rm -rf /boot/initramfs-$REMOVE_KERNEL.img /boot/initramfs-${REMOVE_KERNEL}kdump.img /boot/symvers-$REMOVE_KERNEL.gz /boot/System.map-$REMOVE_KERNEL /boot/vmlinuz-$REMOVE_KERNEL /boot/config-$REMOVE_KERNEL
grubby --remove-kernel=/boot/vmlinuz-$REMOVE_KERNEL

    5. Set the latest remaining kernel as the default boot kernel.

      1. View all installed kernels: 

        grubby --info=ALL

      2. View the current default boot kernel: 

        grubby --default-kernel

        Example output: 

        [root@iZbp104w56ovfyfxy9o**** ~]# grubby --default-kernel
/boot/vmlinuz-3.10.0-1160.90.1.el7.x86_64

      3. Set the latest kernel as the default.

        In this example, 3.10.0-1160.76.1.el7.x86_64 is set as the default boot kernel. 

        grubby --set-default /boot/vmlinuz-3.10.0-1160.76.1.el7.x86_64

    6. After you resolve the network issue, run the SMC client to retry the operation. For more information, see Run the SMC client.