--- title: "Check for Linux VM booting issues by entering the GRUB mode" slug: "linux-grub-boot-issue-vpc" updated: 2026-09-17T09:17:55Z published: 2026-09-17T09:17:55Z canonical: "guide.ncloud-docs.com/linux-grub-boot-issue-vpc" --- > ## Documentation Index > Fetch the complete documentation index at: https://guide.ncloud-docs.com/llms.txt > Use this file to discover all available pages before exploring further. # Check for Linux VM booting issues by entering the GRUB mode Available in VPC If GRUB-related files are corrupted or deleted, Linux may not boot properly and instead enter the GRUB prompt (grub rescue> or grub>). The system may enter GRUB mode for various reasons, and NAVER Cloud does not provide technical support for this issue. For more information on GRUB, see the official document provided by the Linux OS vendor. Note In case the system fails to boot and enters the GRUB prompt after updating the entire package with the dnf (yum) update in XEN-based Rockey Linux 8 VM, see [Check for booting issues after XEN-based Rocky Linux 8 update](/docs/en/xen-rocky8-grub-boot-issue). Caution Before an OS kernel patch or package update, create and thoroughly validate My server image to apply the kernel patch or package update to actual services. Any issues caused by OS updates fall under the responsibility of the customer, and technical support for these issues is not provided. This guide is reference-only to help you troubleshoot issues yourself, and it is applicable in the KVM environment. ## Delete grub.cfg file to forcibly enter GRUB mode Caution If you perform this on a running VM, the system cannot be recovered and data may be lost. Do not perform the same test on a running VM. This guide shows how to forcibly enter the GRUB mode for explanatory purposes. ### RedHat-based OSes (NAVIX, Rocky Linux, and RedHat Enterprise Linux) 1. Access the server remotely. 2. Delete the grub.cfg file. ``` [root@kvm-rockylinux810 ~]# rm /boot/grub2/grub.cfg rm: remove regular file '/boot/grub2/grub.cfg'? y ``` ``` [root@kvm-rockylinux96 ~]# rm /boot/grub2/grub.cfg rm: remove regular file '/boot/grub2/grub.cfg'? y ``` - Rocky Linux 8 - Rocky Linux 9 3. Reboot the VM. ``` [root@kvm-rockylinux810 ~]# sync;reboot ``` 4. If the server does not boot properly, use the **Server access console** menu in the MC console. ![linux-grub-mode_rocky-01](https://cdn.document360.io/6998976f-9d95-4df8-b847-d375892b92c2/Images/Documentation/linux-grub-mode_rocky-01.png?sv=2026-02-06&spr=https&st=2026-11-14T05%3A16%3A22Z&se=2026-11-14T06%3A16%3A22Z&sr=c&sp=r&sig=UL4ITvPRolAoxm0lq9C0pyaSGb6WitecwnHRAJjJx%2F8%3D) ### Ubuntu OS 1. Access the server remotely. 2. Delete the grub.cfg file. ``` root@kvm-ubuntu2204:~# rm /boot/grub/grub.cfg rm: remove regular file '/boot/grub/grub.cfg'? y ``` ``` root@kvm-ubuntu2404:~# rm /boot/grub/grub.cfg rm: remove regular file '/boot/grub/grub.cfg'? y ``` - Ubuntu 22.04 - Ubuntu 24.04 3. Reboot the VM. ``` [root@kvm-ubuntu2204 ~]# sync;reboot ``` 4. If the server does not boot properly, use the **Server access console** menu in the MC console. ![linux-grub-mode_ubuntu-01](https://cdn.document360.io/6998976f-9d95-4df8-b847-d375892b92c2/Images/Documentation/linux-grub-mode_ubuntu-01.png?sv=2026-02-06&spr=https&st=2026-11-14T05%3A16%3A22Z&se=2026-11-14T06%3A16%3A22Z&sr=c&sp=r&sig=UL4ITvPRolAoxm0lq9C0pyaSGb6WitecwnHRAJjJx%2F8%3D) ## How to boot OS after entering GRUB mode Note Once in GRUB mode, the system cannot boot under all circumstances. If you cannot boot the system with the following method, copy the necessary data using the recovery method with Snapshot and return the existing VM. ### RedHat-based OSes (NAVIX, Rocky Linux, and RedHat Enterprise Linux) 1. Check whether the file system can be accessed properly. ![linux-grub-mode_rocky-02](https://cdn.document360.io/6998976f-9d95-4df8-b847-d375892b92c2/Images/Documentation/linux-grub-mode_rocky-02.png?sv=2026-02-06&spr=https&st=2026-11-14T05%3A16%3A22Z&se=2026-11-14T06%3A16%3A22Z&sr=c&sp=r&sig=UL4ITvPRolAoxm0lq9C0pyaSGb6WitecwnHRAJjJx%2F8%3D) Note Under normal circumstances, you should be able to see the /grub2/grub.cfg file. However, the file is not visible because it was deleted using the rm command. 2. Inspect the kernel version you want to boot and the associated files. - Rocky Linux 8 ![linux-grub-mode_rocky-03](https://cdn.document360.io/6998976f-9d95-4df8-b847-d375892b92c2/Images/Documentation/linux-grub-mode_rocky-03.png?sv=2026-02-06&spr=https&st=2026-11-14T05%3A16%3A22Z&se=2026-11-14T06%3A16%3A22Z&sr=c&sp=r&sig=UL4ITvPRolAoxm0lq9C0pyaSGb6WitecwnHRAJjJx%2F8%3D) - Rocky Linux 9 ![linux-grub-mode_rocky-04](https://cdn.document360.io/6998976f-9d95-4df8-b847-d375892b92c2/Images/Documentation/linux-grub-mode_rocky-04.png?sv=2026-02-06&spr=https&st=2026-11-14T05%3A16%3A22Z&se=2026-11-14T06%3A16%3A22Z&sr=c&sp=r&sig=UL4ITvPRolAoxm0lq9C0pyaSGb6WitecwnHRAJjJx%2F8%3D) 3. Attempt to boot by entering the following GRUB commands: Note The following kernels are used in the following example: Rocky Linux 8 : 4.18.0-553.51.1.el8_10.x86_64 Rocky Linux 9 : 5.14.0-570.18.1.el9_6.x86_64 You can select versions other than this one. ``` grub> set root=(hd0,msdos1) grub> linux /vmlinuz-4.18.0-553.51.1.el8_10.x86_64 root=/dev/vda2 ro net.ifnames=0 console=ttyS0,115200n8 console=tty0 grub> initrd /initramfs-4.18.0-553.51.1.el8_10.x86_64.img grub> boot ``` ``` grub> set root=(hd0,msdos1) grub> linux /vmlinuz-5.14.0-570.18.1.el9_6.x86_64 root=/dev/vda2 ro net.ifnames=0 console=ttyS0,115200n8 console=tty0 grub> initrd /initramfs-5.14.0-570.18.1.el9_6.x86_64.img grub> boot ``` - Rocky Linux 8 - Rocky Linux 9 4. After the system boots, log in to the server and recreate the grub.cfg file. ``` # grub2-mkconfig -o /etc/grub2.cfg ``` To return to the In operation status, click **[Force stop]** in the MC console to end the VM and then restart it. 5. If booting still fails after trying the above, create a snapshot of the affected VM, mount it on another VM, and copy the data. When the server cannot be recovered, see [Recover server > How to recover data through snapshot when the server cannot be recovered](/docs/en/server-ts-repair-vpc). ### Ubuntu OS 1. Check if the file system is normal. ![linux-grub-mode_ubuntu-02](https://cdn.document360.io/6998976f-9d95-4df8-b847-d375892b92c2/Images/Documentation/linux-grub-mode_ubuntu-02.png?sv=2026-02-06&spr=https&st=2026-11-14T05%3A16%3A22Z&se=2026-11-14T06%3A16%3A22Z&sr=c&sp=r&sig=UL4ITvPRolAoxm0lq9C0pyaSGb6WitecwnHRAJjJx%2F8%3D) Note Under normal circumstances, you should be able to see the /boot/grub/grub.cfg file. However, the file is not visible because it was deleted using the rm command. 2. Inspect the kernel version you want to boot and the associated files. - Ubuntu 22.04 ![linux-grub-mode_ubuntu-03](https://cdn.document360.io/6998976f-9d95-4df8-b847-d375892b92c2/Images/Documentation/linux-grub-mode_ubuntu-03.png?sv=2026-02-06&spr=https&st=2026-11-14T05%3A16%3A22Z&se=2026-11-14T06%3A16%3A22Z&sr=c&sp=r&sig=UL4ITvPRolAoxm0lq9C0pyaSGb6WitecwnHRAJjJx%2F8%3D) - Ubuntu 24.04 ![linux-grub-mode-ubuntu-04](https://cdn.document360.io/6998976f-9d95-4df8-b847-d375892b92c2/Images/Documentation/linux-grub-mode-ubuntu-04.png?sv=2026-02-06&spr=https&st=2026-11-14T05%3A16%3A22Z&se=2026-11-14T06%3A16%3A22Z&sr=c&sp=r&sig=UL4ITvPRolAoxm0lq9C0pyaSGb6WitecwnHRAJjJx%2F8%3D) 3. Attempt to boot by entering the following GRUB commands: Note The following kernels are used in the following example: You can select versions other than this one. - Ubuntu 22.04 : 5.15.0-140-generic - Ubuntu 24.04 : 6.8.0-84-generic ``` grub> set root=(hd0,gpt2) grub> linux /boot/vmlinuz-5.15.0-140-generic root=/dev/vda2 ro net.ifnames=0 console=ttyS0,115200n8 console=tty0 grub> initrd /boot/initrd.img-5.15.0-140-generic grub> boot ``` ``` grub> set root=(hd0,gpt2) grub> linux /boot/vmlinuz-6.8.0-84-generic root=/dev/vda2 ro net.ifnames=0 console=ttyS0,115200n8 console=tty0 grub> initrd /boot/initrd.img-6.8.0-84-generic grub> boot ``` - Ubuntu 22.04 - Ubuntu 24.04 4. After the system boots, log in to the server and recreate the grub.cfg file. ``` # update-grub ``` To return to the In operation status, click **[Force stop]** in the MC console to end the VM and then restart it. 5. If booting still fails after trying the above, create a snapshot of the affected VM, mount it on another VM, and copy the data. When the server cannot be recovered, see [How to recover data through snapshot when the server cannot be recovered](/docs/en/server-ts-repair-vpc#%EC%84%9C%EB%B2%84-%EB%B3%B5%EA%B5%AC-%EB%B6%88%EA%B0%80-%EC%8B%9C-%EC%8A%A4%EB%83%85%EC%83%B7%EC%9D%84-%ED%86%B5%ED%95%9C-%EB%8D%B0%EC%9D%B4%ED%84%B0-%EB%B3%B5%EA%B5%AC-%EB%B0%A9%EB%B2%95). ## FAQs ### Q. In the example of GRUB command execution process, is net.ifnames=0 console=ttyS0,115200n8 console=tty0 required? For KVM VM, that option is a required boot option. A brief explanation of this option is as follows: - net.ifnames=0 :: Sets the network interface device name to eth0. - biosdevname=0 :: This option is deprecated in newer OS versions. - console=ttyS0,115200n8 console=tty0 :: This option specifies the device to use as the console and configures the system to use the serial port console. Without this option, the system may appear to hang during boot, making it difficult to verify successful booting. After booting the OS, you can check the boot option with the cat /proc/cmdline command. In the /etc/default/grub file, this option is included in GRUB_CMDLINE_LINUX. So, do not delete this option. For more information, see the document provided by your OS vendor.