195 lines
11 KiB
Plaintext
195 lines
11 KiB
Plaintext
! Appendix
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!! Troubleshooting
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Many common problems are answered in the FAQ document, so if you experience problems please check whether the
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[[http://crux.nu/Main/Faq | CRUX FAQ]] contains answers to your questions already.
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If you have further questions, there's a dedicated mailing list for CRUX, and an IRC channel. Actual information about these can be found on the [[Community]] page.
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[[#grubcfg-manually]]
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!! Writing a grub config file by hand
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If %fn%grub-mkconfig%% does not work (eg., because you saved the kernel image under a non-standard name), a grub.cfg file can be created manually. For more information see the GRUB manual at [[http://www.gnu.org/software/grub/manual/]]. A simple example configuration might look like the following:
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[@
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# Display the menu for 10 seconds
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set timeout=10
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# Boot the first entry by default
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set default=0
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# Boot entries follow
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# Default CRUX boot entry
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menuentry "CRUX 3.7" {
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linux (hd0,msdos2)/boot/vmlinuz-5.15.55 root=/dev/sda2 quiet
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}
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# Single-user recovery entry
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menuentry "CRUX 3.7 single-user mode" {
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linux (hd0,msdos2)/boot/vmlinuz-5.15.55 root=/dev/sda2 quiet single
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}
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# Memory test entry
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menuentry "MemTest86+ 4.20" {
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linux16 (hd0,msdos2)/boot/memtest86+-4.20.bin
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}
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@]
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Save the manual configuration file as '''/boot/grub/grub.cfg'''.
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[[#syslinux-install]]
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!! SYSLINUX installation notes
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The venerable bootloader LILO has been dropped as of CRUX version 3.7; most users will find it straightforward to adopt
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GRUB instead. This section presents another option, the SYSLINUX bootloader.
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!!! Precaution
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Installing a new boot manager is like modifying the partition table using fdisk 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 is as simple as copying a few files to the
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EFI system partition (mounted at %fn%/boot/efi%% in the example commands below) and writing a configuration that tells
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syslinux where to find your kernel. First confirm that EFI variables are visible to the currently-running kernel; if you run
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@@efivar -l@@ and see a list of %fn%universally-unique-identifier-VariableName%%s, then the following commands should be
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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 system partition.
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-> Observe that the EFI bootloader was given a generic name in the fourth line above. If you had saved it in
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%fn%/boot/efi/BOOT%% using the original filename provided by the '''syslinux''' package, then it would have been
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necessary to run @@efibootmgr@@ to inform the BIOS about this new bootloader-like object. See [[#EFI-stub-install | "EFI Stub installation"]] 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 information) in the working directory. The final
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command starts the vi editor on a buffer that will be written to %fn%syslinux.cfg%%, which must contain a line giving the
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path to the kernel image. See the [[#syslinux-cfg| "SYSLINUX configuration file template"]] for details.
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!!! Installation -- Legacy (BIOS) booting
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If your motherboard does not support UEFI boot mode (or if you disabled it deliberately), then installing syslinux will
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require you to overwrite the master boot record (MBR). The '''syslinux''' package provides two different binary
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blobs that can occupy the designated MBR area of the hard disk. To determine which binary blob is appropriate, you will
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need to remember what kind of partition table you wrote when you initialized your disk for CRUX. The older DOS (MBR)
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partition table is supported by %fn%/usr/share/syslinux/mbr.bin%%, while the newer GPT (GUID) partition table is supported
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by %fn%/usr/share/syslinux/gptmbr.bin%%. You can run @@fdisk -l /dev/sda@@ (replacing ''sda'' with your actual device) to
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remind yourself what the existing partition table looks like. An identification of the exact partition type (DOS or GPT)
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will appear next to ''Disklabel type:'' in the fdisk output.
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Once you determine the binary blob that will work with your partition table, run the commands that will copy that
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binary blob into the master boot record. '''Remember to replace ''sda'' with your actual device.'''
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$ PTYPE=$(fdisk -l /dev/sda | grep "^Disklabel type" | cut -d " " -f3)
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$ [ "$PTYPE" = "gpt" ] && BINBLOB=gptmbr.bin || BINBLOB=mbr.bin
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$ mkdir -p /boot/efi/BOOT
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$ cd /boot/efi/BOOT
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$ cp /usr/share/syslinux/ldlinux.c32 .
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$ extlinux --install /boot/efi/BOOT/
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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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-> The @@extlinux@@ command takes a ''directory of the mounted EFI system partition'' as its argument, rather
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than a device node. Upstream documentation begins with an example of calling the @@syslinux@@ command with the
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''device node'' as its argument, which assumes that the EFI system partition is not mounted. Because you're already
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creating files on this partition, we prefer the command that won't require you to unmount the partition before running it.
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The @@extlinux@@ command is also smart enough to set its argument (the ''install target'') as the directory to be searched
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for configuration files, so you can proceed to launch the editor on %fn%syslinux.cfg%% (see the next section for a
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template) without changing directory.
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[[#syslinux-cfg]]
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!!! Template for a SYSLINUX configuration file
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Now that the SYSLINUX bootloader is successfully installed, you need to tell it where to find your kernel and the root
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filesystem.
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[@
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default CRUX-3.7
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prompt 1
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timeout 10
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label CRUX-3.7
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say "Now booting into CRUX"
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kernel vmlinuz-5.15.55
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append root=/dev/sda2 rw quiet
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@]
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When giving the location of a kernel image, relative paths are interpreted in reference to the %fn%syslinux.cfg%% file. In
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the example above, where @@extlinux@@ assigned %fn%/boot/efi/BOOT/%% as the preferred location for %fn%syslinux.cfg%%, the
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kernel would have to be copied to %fn%/boot/efi/BOOT/vmlinuz-5.15.55%%. Saving kernels here (in the BOOT subdirectory of
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the EFI system partition) is a common practice when using the kernel itself as a bootloader; see the next section for more
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details.
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[[#EFI-stub-install]]
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!! EFI Stub installation notes
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GRUB and SYSLINUX offer the most familiar experience for users coming from LILO. After a one-time interaction with the
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BIOS and the Master Boot Record, all subsequent updates to the GRUB or SYSLINUX configuration only involve editing a
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flat-text file, and the contents of the bootsector or the NVRAM never need to be revisited. But if you aren't intimidated
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by the prospect of manipulating EFI variables directly, another option is to let the Linux kernel image provide the EFI
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bootloader code itself.
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-> Note: this type of booting only works in UEFI mode, and when your kernel has been built with ''CONFIG_EFI_STUB=y''.
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Legacy MBR booting is not supported with this method.
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As with GRUB and SYSLINUX, the kernel has to be told which device to use as a root filesystem. Most modern BIOSes allow
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you to append options like ''root=/dev/sda2'' to the line that boots the kernel, but some buggy UEFI implementations do
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not honor such appended options. To be safe, you can customize the boot options during the kernel configuration process
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(the @@make menuconfig@@ step), at the expense of making it harder to put the disk in an external enclosure and boot from
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USB (when you want to travel lightly). If you leave the boot options empty during kernel configuration, and the BIOS does
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not honor your appended options, you might have to boot from a rescue disk to get back into your system and fix things.
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* Copy your built kernel to the BOOT subdirectory of the EFI system partition (mounted at %fn%/boot/efi%%). For maximum
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compatibility, save it with the 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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$ 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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* Finally, change the boot order so that the newly-created boot entry is the first one tried. Start by finding the number
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assigned to the newly-created entry, and then use that number to specify the desired boot order.
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[@
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$ 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,d5a44413-5bea-b24c-b4b7-76b32d5d2ed4,0x800,0x64000)/File(\BOOT\vmlinuz-5.15.26.efi)72006f006f0074...
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Boot0001* Linux 5.15.55 HD(1,GPT,d5a44413-5bea-b24c-b4b7-76b32d5d2ed4,0x800,0x64000)/File(\BOOT\vmlinuz-5.15.55.efi)72006f006f0074...
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$ efibootmgr -o 0001,0000
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@]
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[[#initramfs]]
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!! Notes on Initramfs
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A common scenario that prevents the usual practice of booting a slimmed-down kernel containing only the drivers for the
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root filesystem (and then loading modules to initialize other hardware) is that the root filesystem is not a physical
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volume, but rather a logical volume inside an encryption layer like LUKS. To handle this situation, you will need to go
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beyond the kernel building process outlined above, and also create a compressed filesystem image (called an ''initramfs'')
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that contains the lvm and cryptsetup packages (and the drivers for usb input devices, if you chose not to compile them
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into the kernel). Creating such an initramfs was once an intricate procedure, but tools like '''dracut''' make it much
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simpler these days.
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If running @@dracut@@, and saving the initramfs alongside the kernel in the EFI system partition, had been the only
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deviations from the usual CRUX installation procedure, then one section of the appendix would suffice to explain how to do
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full-disk encryption in CRUX. But preparation for this setup begins at the partitioning stage, when you need to call
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commands from the '''lvm2''' and '''cryptsetup''' packages before creating and mounting your filesystems. So this section
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of the appendix just points to a separate document, where an
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[[https://gitlab.com/SiFuh/Documentation/-/blob/master/CRUX-3.6-Encrypted.txt | outline for installing CRUX with full-disk
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encryption]] is given from beginning to end. Even if full-disk encryption is not your desired endpoint and you just want
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to learn more about highly-modular kernel configs, the creation of an initramfs is best viewed in the context of the
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overall installation procedure, after having successfully built some less-modular kernels yourself. Studying the upstream
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documentation for any unfamiliar command in the linked outline (eg., %fn%cryptsetup%%, %fn%pvcreate%%, or %fn%dracut%%)
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is an excellent way to distinguish the functions performed by the various components.
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