чување 29d33809fabdc61e9050a92cb33bd7ac4b7fee4b
родитељ b87980bb31d303e1e339ebbf8335ed6f2a5a6888
Аутор: Страхиња Радић <contact@strahinja.org>
Датум: Thu, 20 Apr 2023 16:57:20 +0200
BOOTING: Update to reflect switch to initramfs
Signed-off-by: Страхиња Радић <contact@strahinja.org>
Diffstat:
| M | BOOTING | | | 85 | +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-------------------- |
измењених датотека: 1, додавања: 64(+), брисања: 21(-)
diff --git a/BOOTING b/BOOTING
@@ -15,7 +15,8 @@ two is used depends on your system. If you can run
$ efibootmgr -v
and it doesn't give an error message but a list of boot entries, then you have
-UEFI.
+UEFI. With Linux as kernel, a mounted efivarfs, usually at
+/sys/firmware/efi/efivars, is also needed for the above command to work.
Partition table type
@@ -51,25 +52,41 @@ on the system root partition. This can be done in two ways:
* By creating an initial root partition (initramfs) having a temporary init
program, which if needed handles loading the necessary kernel modules
- (drivers) to access the root partition. This method supports advanced
- partition selection, for example by their UUIDs or PARTUUIDs, and doesn't
+ (drivers) to access the root partition. This method also supports advanced
+ partition selection, for example by their UUIDs or LABELs, and doesn't
require the support for filesystem type of the root partition to be compiled
- in the kernel.
+ into the kernel. initramfs is passed to EFISTUB through the kernel command
+ line: `initrd=\initramfs.img`, where the "root" directory is ESP.
-* By specifying the root partition on the kernel command line (through a kernel
- parameter), for example `root=/dev/sda2`. This is more minimal, as it doesn't
- require initramfs, but prone to being unable to boot a system if the disk
- configuration is changed, for example by plugging in a USB flash drive or
- otherwise changing the order of the hard disks. Alternatively, partition can
- be specified by PARTUUID, which uniquely identifies a partition on GPT
- systems: `root=PARTUUID=...`. This is the recommended approach in Galeb.
+ Note that UEFI uses DOS filesystem path separator, backslash (\),
+ instead of a slash (/) used on Unix-like systems.
+
+* By compiling the necessary filesystem modules and storage device drivers into
+ the kernel and specifying the root partition on the kernel command line. This
+ is more minimal, as it doesn't require initramfs. However, advanced partition
+ selection by UUIDs and LABELs is not supported (but see below), and licenses
+ for "binary blobs" (drivers/modules) usually clash with the requirements of
+ GPL (which is the license of the kernel), preventing them from being compiled
+ in the kernel in such a way. That's why initramfs is the most used option, and
+ recommended in Galeb. In Galeb, there is a script mkinitramfs(8), which can be
+ used to generate initramfs. Refer to [5].
+
+Partition can always be specified by a device pathname, such as
+`root=/dev/sda2`, which can lead to boot failure if the storage device driver
+(kernel module) is inaccessible or the disk configuration is changed. For
+example, this can happen when plugging in a USB flash drive or physically
+connecting hard drives to different cables, and rebooting, or otherwise changing
+the order of hard disks.
+
+Partition on GPT systems can also be specified by PARTUUID, which uniquely
+identifies a partition: `root=PARTUUID=...`. This is the recommended approach.
Recommended setup in Galeb
--------------------------
-The following is the basic recommended partition configuration in Galeb. It
-assumes an UEFI/GPT system.
+The following is the basic recommended partition configuration in Galeb on the
+traditional SCSI drives. It assumes an UEFI/GPT system.
Partition Mountpoint Filesystem Type Size
--------------------------------------------------------------
@@ -81,10 +98,27 @@ include
root=/dev/sda2
+or
+
+ root=PARTUUID=[PARTUUID of /dev/sda2]
+
and that the ESP is in /dev/sda1, mounted later during the boot process to
/boot. This is where the kernel stub should go into, and will later be
accessible from the booted system at /boot/vmlinuz.
+When the partition /dev/sda2 exists, its PARTUUID can be obtained with the
+command
+
+ $ lsblk -no PARTUUID /dev/sda2
+
+NVME SSDs require the nvme and nvme_core kernel modules, and the partition
+device pathnames usually become /dev/nvme0n1p1 and /dev/nvme0n1p2, respectively:
+
+ Partition Mountpoint Filesystem Type Size
+ --------------------------------------------------------------
+ /dev/nvme0n1p1 /boot vfat (32-bit) ~500MB
+ /dev/nvme0n1p2 / ext4 Rest
+
Creating a boot entry in efibootmgr
-----------------------------------
@@ -92,8 +126,17 @@ Creating a boot entry in efibootmgr
The necessary command line parameters will be briefly explained here. For more
information, see `man 8 efibootmgr` and `efibootmgr -h`.
+ partuuid=$(lsblk -no PARTUUID /dev/sda2)
efibootmgr -c -d /dev/sda -l '\vmlinuz' -L 'Galeb EFISTUB' -p1 \
- -u 'root=/dev/sda2 ro'
+ -u 'initrd=\initramfs.img root=PARTUUID='${partuuid}' ro'
+
+
+Explanation
+-----------
+
+partuuid=$(lsblk -no PARTUUID /dev/sda2)
+ Obtain the PARTUUID of /dev/sda2 and store it in the shell variable
+ `partuuid`.
-c Create a new boot entry.
@@ -101,9 +144,7 @@ information, see `man 8 efibootmgr` and `efibootmgr -h`.
Disk on which the root partition is (boot disk).
-l '\vmlinuz'
- Boot loader (our EFISTUB) is in the file vmlinuz on ESP. UEFI uses DOS
- filesystem path separator, backslash (\), instead of a slash (/) used on
- Unix-like systems.
+ Boot loader (our EFISTUB) is in the file vmlinuz on ESP.
-L 'Galeb EFISTUB'
Label for the boot entry.
@@ -112,8 +153,9 @@ information, see `man 8 efibootmgr` and `efibootmgr -h`.
-u Treat the kernel command line as UCS-2.
-'root=/dev/sda2 ro'
- Kernel command line, quoted to prevent parsing by the shell.
+'initrd=\initramfs.img root=PARTUUID='${partuuid}' ro'
+ Kernel command line, quoted to prevent parsing by the shell. Value of
+ the shell variable `partuuid` is inserted where needed.
Boot image
@@ -123,11 +165,11 @@ After the boot scripts have finished, you will be presented with a choice to
create a boot image. The boot image will be compressed with xz and needs to be
sent to a USB flash medium, for example:
- # xz -dc galeb-2.2-x86_64-20220913.raw.xz > /dev/sdb
+ # xz -dc galeb-2.2-x86_64-20230417.raw.xz > /dev/sdb
or, if you have pv[4]:
- # xz -dc galeb-2.2-x86_64-20220913.raw.xz | pv > /dev/sdb
+ # xz -dc galeb-2.2-x86_64-20230417.raw.xz | pv > /dev/sdb
_Be careful when specifying the device you send the output to, in order to not
overwrite any existing partitions (your hard disk, etc)!_ You can find out the
@@ -160,3 +202,4 @@ See also
2. https://wiki.archlinux.org/title/EFI_system_partition
3. https://wiki.archlinux.org/title/EFISTUB
4. http://www.ivarch.com/programs/pv.shtml
+5. https://git.sr.ht/~strahinja/galeb-mkinitramfs/
