rename-efi-entry

A Bash script to rename EFI boot entries

Background

EFI / UEFI, boot configurations

EFI / UEFI is a specification that defines a software interface between an operating system and platform firmware. It is intended by hardware manufacturers to replace the legacy BIOS firmware interface.

In particular this specification allows to define OS boot configurations to be executed upon system power on. These boot configurations specify disk partitions to boot from and are typically identified by their text labels that are listed in "Startup" / "Boot" EFI setup section. These boot configurations may be optionally selectable upon system startup.

The problem

Operating system installation routines tend to have these boot configuration entry labels hard-coded and to create them in EFI PROM automatically. So in case a computer has, say, several Ubuntu instances installed, it is also likely to have several identical "ubuntu" boot configuration labels in its EFI menus, causing a kind of confusion.

One might further want to rename boot configurations, so to make them distinguishable, but unfortunately the standard efibootmgr utility has no option for that. It is only possible to delete a boot configuration entry and re-create it with a new label. Meanwhile, the data that is necessary for re-creating a boot configuration entry is not trivial and requires certain inquiries into EFI configuration and disk partition attributes.

The script

The rename-efi-entry script is designed to facilitate renaming EFI boot configuration entries using efibootmgr utility. It automates querying current EFI configuration and bootable partition data, and also shaping command line arguments for efibootmgr.

Usage

sudo ./rename-efi-entry existing_efi_label new_efi_label [bootnum]

Table 1. Command line arguments

`existing_efi_label`	existing EFI entry label to be renamed
`new_efi_label`	the new label value to be assigned
`bootnum`	optional: the `bootnum` value of the EFI entry to be renamed, required in case of repeating label values to avoid ambiguity

E.g.:

sudo ./rename-efi-entry ubuntu 'ubuntu 18.04'

or in case of multiple boot entries labeled as 'ubuntu':

sudo ./rename-efi-entry ubuntu 'ubuntu 18.04' 0001

In case of doubt bootnum values may be clarified using efibootmgr --verbose command:

$ efibootmgr --verbose
BootCurrent: 0001
Timeout: 0 seconds
BootOrder: 0002,0001,0017,001B,0000,0016,0019,001A,0018
Boot0000  Windows Boot Manager	HD(1,MBR,0x5092863d,0x3cde8c,0x1340)/File(\EFI\Microsoft\Boot\bootmgfw.efi)WINDOWS...
Boot0001* ubuntu            	HD(1,GPT,2ffcc127-f6ce-40f0-9932-d1dfd14e9462,0x800,0x100000)/File(\EFI\ubuntu\shimx64.efi)
Boot0002* ubuntu            	HD(1,GPT,cba13b09-d754-4d31-9719-369fa60928d1,0x800,0x100000)/File(\EFI\ubuntu\shimx64.efi)
Boot0010  ...

Required bootnum values (e.g. 0001 from Boot0001) may be further identified by checking corresponding uuid values (e.g. 2ffcc127-f6ce-40f0-9932-d1dfd14e9462) against values provided by sfdisk -d command, e.g.:

$ sudo sfdisk -d /dev/sda
label: gpt
label-id: 0560DAA2-3010-47A2-B083-047C813F0A04
device: /dev/sda
unit: sectors
first-lba: 34
last-lba: 1953525134

/dev/sda1 : start=        2048, size=     1048576, type=C12A7328-F81F-11D2-BA4B-00A0C93EC93B, uuid=2FFCC127-F6CE-40F0-9932-D1DFD14E9462, name="EFI System Partition"
/dev/sda2 : start=     1050624, size=   102400000, type=0FC63DAF-8483-4772-8E79-3D69D8477DE4, uuid=A06790C2-3818-4F57-84EF-4D1B9FFB417E, name="SSD system"
/dev/sda3 : start=   103450624, size=  1850073088, type=0FC63DAF-8483-4772-8E79-3D69D8477DE4, uuid=67A374C2-081E-477E-945C-78BE129A2044, name="SSD data"

Implementation details

What the script does under the hood, is:

obtain a list of disk devices using lsblk;
obtain a list of disk partitions and their uuid values for every disk device using sfdisk;
obtain a list of EFI boot entries using efibootmgr;
filter EFI boot entries against existing_efi_label value, supplied by the user as command line argument;
make sure that this boot entry identification is unique, using bootnum if necessary;
extract uuid value from the EFI boot entry to be renamed, and use it to identify the relevant disk partition and its device name;
verify matching of partition numbers between EFI boot entry and partition device name;
shape the commands for efibootmgr to delete the existing EFI boot entry and to create a new one with required label;
ask final user consent;
apply the efibootmgr commands.

Limitations

This script can only rename EFI boot entries that are related to Linux. It will most probably ignore the other ones.

Important usage notes

Feel free to use, but do it on your risk :)

It may be wise to review the efibootmgr commands before final execution…

CanasSimon/rename-efi-entry