UEFI installation: ensure better agreement among paths in the example commands
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@ -55,38 +55,6 @@ another option, the SYSLINUX bootloader.
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Installing a new boot manager is like modifying the partition table using fdisk
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or installing a new system kernel. Please create a rescue boot disk first!
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!!! Installation -- UEFI booting
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If your motherboard supports the UEFI boot mode, then installation of syslinux
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is as simple as copying a few files to the EFI system partition (mounted at
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%fn%/boot/efi%% in the example commands below) and writing a configuration that
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tells syslinux where to find your kernel. First confirm that EFI variables are
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visible to the currently-running kernel; if you run @@efivar -l@@ and see a list
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of %fn%universally-unique-identifier-VariableName%%s, then the following
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commands should be sufficient.
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$ mkdir -p /boot/efi/BOOT
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$ cd /boot/efi/BOOT
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$ cp /usr/share/syslinux/efi64/ldlinux.e64 .
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$ cp /usr/share/syslinux/efi64/syslinux.efi BOOTX64.EFI
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$ cp /usr/src/linux-5.15.55/arch/x86/boot/bzImage vmlinuz-5.15.55
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$ vi syslinux.cfg
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-> Remember to change %fn%/boot/efi%% to the actual mount point of your EFI
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system partition.
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-> Observe that the EFI bootloader was given a generic name in the fourth line
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above. If you had saved it in fn%/boot/efi/BOOT%% using the original filename
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provided by the '''syslinux''' package, then it would have been necessary to run
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@@efibootmgr@@ to inform the BIOS about this new bootloader-like object. See
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[[#EFI-stub-install | "EFI Stub installation"]] for an example of using
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@@efibootmgr@@ to create new boot entries.
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-> The fifth command puts a copy of the kernel (renamed to show version
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information) in the working directory. The final command starts the vi editor on
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a buffer that will be written to %fn%syslinux.cfg%%, which must contain a line
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giving the path to the kernel image. See the [[#syslinux-cfg| "SYSLINUX
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configuration file template"]] for details.
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!!! Installation -- Legacy (MBR) booting
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If your motherboard does not support UEFI boot mode (or if you disabled it
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deliberately), then installing syslinux will require you to overwrite the master
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@ -116,6 +84,7 @@ BIOSes that truly have no UEFI capability.'''
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$ mkdir -p $INSTALLDIR
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$ cd $INSTALLDIR
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$ cp /usr/share/syslinux/ldlinux.c32 .
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$ cp /usr/src/linux-5.15.55/arch/x86/boot/bzImage vmlinuz-5.15.55
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$ extlinux --install $INSTALLDIR
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$ dd bs=440 count=1 conv=notrunc if=/usr/share/syslinux/$BINBLOB of=/dev/sda
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$ vi syslinux.cfg
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@ -149,11 +118,43 @@ label CRUX-3.7
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@]
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When giving the location of a kernel image, relative paths are interpreted in
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reference to the %fn%syslinux.cfg%% file. In the example above, if
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reference to the %fn%syslinux.cfg%% file. In the example above, since
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@@extlinux@@ assigned %fn%/boot/efi/EFI/BOOT/%% as the preferred location for
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%fn%syslinux.cfg%%, the kernel would have to be copied to
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%fn%syslinux.cfg%%, we copied the kernel to
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%fn%/boot/efi/EFI/BOOT/vmlinuz-5.15.55%%.
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!!! Installation -- UEFI booting
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If your motherboard supports the UEFI boot mode, then installation of syslinux
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is as simple as copying a few files to the EFI system partition (mounted at
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%fn%/boot/efi%% in the example commands below) and writing a configuration that
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tells syslinux where to find your kernel. First confirm that EFI variables are
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visible to the currently-running kernel; if you run @@efivar -l@@ and see a list
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of %fn%universally-unique-identifier-VariableName%%s, then the following
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commands should be sufficient.
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$ mkdir -p /boot/efi/EFI/BOOT
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$ cd /boot/efi/EFI/BOOT
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$ cp /usr/share/syslinux/efi64/ldlinux.e64 .
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$ cp /usr/share/syslinux/efi64/syslinux.efi BOOTX64.EFI
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$ cp /usr/src/linux-5.15.55/arch/x86/boot/bzImage vmlinuz-5.15.55
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$ vi syslinux.cfg
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* Remember to change %fn%/boot/efi%% to the actual mount point of your EFI
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system partition.
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* Most UEFI implementations search the subdirectory %fn%EFI/BOOT%% of the
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EFI partition for the bootloader, defaulting to a file named
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%fn%BOOTX64.EFI%% in that subdirectory.
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** If you choose a different mountpoint for the EFI partition, adjust the @@mkdir@@ and @@cd@@ commands accordingly (UEFI itself is completely agnostic about mountpoints specified in %fn%/etc/fstab).
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** Copying the %fn%syslinux.efi%% file with its original name
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would require you to run @@efibootmgr@@ and inform the BIOS about this new
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bootloader-like object. See [[#EFI-stub-install | "EFI Stub installation"]]
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for an example of using @@efibootmgr@@ to create new boot entries.
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* The fifth command puts a copy of the kernel (renamed to show version
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information) in the working directory. The final command starts the vi editor on
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a buffer that will be written to %fn%syslinux.cfg%%, which must contain a line
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giving the path to the kernel image. See the [[#syslinux-cfg| "SYSLINUX
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configuration file template"]] for details.
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[[#EFI-stub-install]]
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!! EFI Stub installation notes
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@ -190,27 +191,15 @@ get back into your system and fix things.
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extension %fn%.efi%%.
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[@
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$ mkdir -p /boot/efi/BOOT
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$ cd /boot/efi/BOOT
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$ mkdir -p /boot/efi/EFI/BOOT
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$ cd /boot/efi/EFI/BOOT
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$ cp /usr/src/linux-5.15.55/arch/x86/boot/bzImage vmlinuz-5.15.55.efi
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@]
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* Next, create a boot entry telling the BIOS about the kernel image you just saved.
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$ efibootmgr -c -d /dev/sda -L 'Linux 5.15.55' -l '\BOOT\vmlinuz-5.15.55.efi' -u 'root=/dev/sda2'
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$ efibootmgr -c -d /dev/sda -L 'Linux 5.15.55' -l '\EFI\BOOT\vmlinuz-5.15.55.efi' -u 'root=/dev/sda2'
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-> For maximum portability, you can also identify the root filesystem using its
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partition UUID. Run @@ls -l /dev/disk/by-partuuid/@@ to discover the UUID of the
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known partitions, and then modify the @@efibootmgr@@ arguments to use the
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identifier of the root partition. '''Note: this option is more fragile than
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specifying the root partition using its device node, because of the delay in
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scanning all partitions to construct the list of their UUIDs. If you encounter
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an error when booting your CRUX system this way, you will have to use the
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installation media (or another rescue disk) to recreate the EFI boot entry with
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device node instead, or with an additional boot option that gives the kernel more
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time to enumerate the partitions.'''
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$ efibootmgr -c -d /dev/sda -L 'Linux 5.15.55' -l '\BOOT\vmlinuz-5.15.55.efi' -u 'root=PARTUUID=c3259ad5-...'
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* Finally, change the boot order so that the newly-created boot entry is the
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first one tried. Start by finding the number assigned to the newly-created
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@ -221,12 +210,27 @@ $ efibootmgr
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BootCurrent: 0000
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Timeout: 1 seconds
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BootOrder: 0000,0001
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Boot0000* Linux 5.15.26 HD(1,GPT,d5a44413-...,0x800,0x64000)/File(\BOOT\vmlinuz-5.15.26.efi)72006f006f0074...
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Boot0001* Linux 5.15.55 HD(1,GPT,d5a44413-...,0x800,0x64000)/File(\BOOT\vmlinuz-5.15.55.efi)72006f006f0074...
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Boot0000* Linux 5.15.26 HD(1,GPT,d5a44413-...,0x800,0x64000)/File(\EFI\BOOT\vmlinuz-5.15.26.efi)72006f006f0074...
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Boot0001* Linux 5.15.55 HD(1,GPT,d5a44413-...,0x800,0x64000)/File(\EFI\BOOT\vmlinuz-5.15.55.efi)72006f006f0074...
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$ efibootmgr -o 0001,0000
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@]
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-> As in the UEFI installation of SYSLINUX, the subdirectory %fn%EFI/BOOT%%
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of the EFI system partition is the default path where the BIOS expects to
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find a bootloader. This location is more obvious in the @@efibootmgr@@
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commands, since @@efibootmgr@@ is agnostic about the mountpoint of your
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EFI system partition. The two most common ways to shorten what looks like an
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overly-verbose path to the kernel image are:
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** mount your EFI system partition somewhere else (and adjust the @@mkdir@@ and @@cd@@ commands as needed).
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** save your kernel closer to the root of the EFI system partition (and change the @@efibootmgr@@ invocation as needed).
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-> The flexibility afforded by all these options can be overwhelming (but
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considerably less so than the decisions involved in full-disk encryption;
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see the next section). Each presentation above (SYSLINUX legacy, SYSLINUX
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UEFI, and EFI STUB) is meant to illustrate just one possible way of setting
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up a bootloader, and you're welcome to explore variations on these
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instructions to suit your preferred partitioning scheme.
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[[#initramfs]]
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!! Notes on Initramfs
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