→ Applies to: SynetoOS 6.x and above

PREREQUISITES
This check is mandatory before upgrading to SynetoOS 6.0.3. It can also be run at any time to verify available space on the /boot partition.

Symptom

During the upgrade from SynetoOS 5 to SynetoOS 6, the process might halt during the post-upgrade reconfiguration phase due to insufficient space in the /boot partition (~405 MB) caused by leftover older kernels. Upon reboot, the system fails to start normally and drops into a GRUB rescue console (grub>).

Solution

Step 1. Connect to SynetoOS appliance via SSH as admin

ssh admin@<your_ip_address_or_hostname>

Step 2. Get root privileges

sudo su -

Step 3. Check available space on the /boot partition

df -h /boot

EXAMPLE OUTPUT

[root@syneto ~]# df -h /boot
Filesystem      Size  Used Avail Use% Mounted on
/dev/md127       405M  298M   107M  74% /boot

If free space is below 150 MB, proceed with below steps to free up space before starting the upgrade.

Step 4. Check which kernels are currently installed

rpm -qa kernel

EXAMPLE OUTPUT

[root@syneto ~]# rpm -qa kernel
kernel-4.18.0-477.27.1.el8_8.x86_64
kernel-4.18.0-513.11.1.el8_9.x86_64
kernel-5.14.0-611.55.1.el9_7.x86_64

Step 5. Cross-check installed kernels against files in /boot

ls -l /boot/vmlinuz-*

EXAMPLE OUTPUT

[root@syneto ~]# ls -l /boot/vmlinuz-*
-rwxr-xr-x. 1 root root 10913432 Nov 17  2023 /boot/vmlinuz-4.18.0-477.27.1.el8_8.x86_64
-rwxr-xr-x. 1 root root 10913432 Apr  4  2024 /boot/vmlinuz-4.18.0-513.11.1.el8_9.x86_64
-rwxr-xr-x. 1 root root 14461768 Apr 16  2025 /boot/vmlinuz-5.14.0-611.55.1.el9_7.x86_64

IMPORTANT
If a kernel version appears in this file listing but not in the output of Step 4, it is still an installed kernel and must be included in the removal step below. Treat the /boot listing as the authoritative source, not rpm -qa kernel alone.

Step 6. Check which kernel is currently running

uname -r

EXAMPLE OUTPUT

[root@syneto ~]# uname -r
5.14.0-611.55.1.el9_7.x86_64

Step 7. Remove old unused kernels (replace <old-version> with versions found in Step 4 & Step 5 that do not match the output of Step 6)

rpm -e --nodeps kernel-core-<old-version>

rpm -e --nodeps kernel-modules-core-<old-version>

rpm -e --nodeps kernel-<old-version>

EXAMPLE

rpm -e --nodeps kernel-core-4.18.0-477.27.1.el8_8.x86_64
rpm -e --nodeps kernel-modules-core-4.18.0-477.27.1.el8_8.x86_64
rpm -e --nodeps kernel-4.18.0-477.27.1.el8_8.x86_64

rpm -e --nodeps kernel-core-4.18.0-513.11.1.el8_9.x86_64
rpm -e --nodeps kernel-modules-core-4.18.0-513.11.1.el8_9.x86_64
rpm -e --nodeps kernel-4.18.0-513.11.1.el8_9.x86_64

IMPORTANT
Run this commands for each old kernel to remove.
Never remove the kernel currently in use (the one shown in Step 6). Only remove kernels whose version does not match the output of Step 6.
--nodeps skips dependency resolution. Using dnf remove instead may propose removing unrelated packages tied to kmod/DKMS modules built against the old kernel (e.g. ZFS modules), even though the old kernel itself is unused.

Step 8. Check that /boot now has sufficient free space before proceeding with the upgrade

df -h /boot

EXAMPLE OUTPUT

[root@syneto ~]# df -h /boot
Filesystem      Size  Used Avail Use% Mounted on
/dev/md127       405M  178M   227M  44% /boot

Check if the free space is greater than 150 MB before starting the upgrade.