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69055103 TL |
1 | [[sysboot]] |
2 | Host Bootloader | |
3 | --------------- | |
62de1c14 SI |
4 | ifdef::wiki[] |
5 | :pve-toplevel: | |
6 | endif::wiki[] | |
7 | ||
69055103 TL |
8 | {pve} currently uses one of two bootloaders depending on the disk setup |
9 | selected in the installer. | |
62de1c14 SI |
10 | |
11 | For EFI Systems installed with ZFS as the root filesystem `systemd-boot` is | |
12 | used. All other deployments use the standard `grub` bootloader (this usually | |
13 | also applies to systems which are installed on top of Debian). | |
14 | ||
69055103 | 15 | [[sysboot_installer_part_scheme]] |
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16 | Partitioning scheme used by the installer |
17 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
18 | ||
19 | The {pve} installer creates 3 partitions on the bootable disks selected for | |
20 | installation. The bootable disks are: | |
21 | ||
22 | * For Installations with `ext4` or `xfs` the selected disk | |
23 | ||
24 | * For ZFS installations all disks belonging to the first `vdev`: | |
25 | ** The first disk for RAID0 | |
26 | ** All disks for RAID1, RAIDZ1, RAIDZ2, RAIDZ3 | |
27 | ** The first two disks for RAID10 | |
28 | ||
29 | The created partitions are: | |
30 | ||
31 | * a 1 MB BIOS Boot Partition (gdisk type EF02) | |
32 | ||
33 | * a 512 MB EFI System Partition (ESP, gdisk type EF00) | |
34 | ||
35 | * a third partition spanning the set `hdsize` parameter or the remaining space | |
36 | used for the chosen storage type | |
37 | ||
38 | `grub` in BIOS mode (`--target i386-pc`) is installed onto the BIOS Boot | |
39 | Partition of all bootable disks for supporting older systems. | |
40 | ||
41 | ||
69055103 | 42 | [[sysboot_grub]] |
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43 | Grub |
44 | ~~~~ | |
45 | ||
46 | `grub` has been the de-facto standard for booting Linux systems for many years | |
47 | and is quite well documented | |
48 | footnote:[Grub Manual https://www.gnu.org/software/grub/manual/grub/grub.html]. | |
49 | ||
50 | The kernel and initrd images are taken from `/boot` and its configuration file | |
51 | `/boot/grub/grub.cfg` gets updated by the kernel installation process. | |
52 | ||
53 | Configuration | |
54 | ^^^^^^^^^^^^^ | |
55 | Changes to the `grub` configuration are done via the defaults file | |
56 | `/etc/default/grub` or config snippets in `/etc/default/grub.d`. To regenerate | |
57 | the `/boot/grub/grub.cfg` after a change to the configuration run: | |
58 | ||
59 | ---- | |
60 | `update-grub`. | |
61 | ---- | |
62 | ||
69055103 | 63 | [[sysboot_systemd_boot]] |
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64 | Systemd-boot |
65 | ~~~~~~~~~~~~ | |
66 | ||
67 | `systemd-boot` is a lightweight EFI bootloader. It reads the kernel and initrd | |
68 | images directly from the EFI Service Partition (ESP) where it is installed. | |
69 | The main advantage of directly loading the kernel from the ESP is that it does | |
70 | not need to reimplement the drivers for accessing the storage. In the context | |
71 | of ZFS as root filesystem this means that you can use all optional features on | |
72 | your root pool instead of the subset which is also present in the ZFS | |
73 | implementation in `grub` or having to create a separate small boot-pool | |
74 | footnote:[Booting ZFS on root with grub https://github.com/zfsonlinux/zfs/wiki/Debian-Stretch-Root-on-ZFS]. | |
75 | ||
76 | In setups with redundancy (RAID1, RAID10, RAIDZ*) all bootable disks (those | |
77 | being part of the first `vdev`) are partitioned with an ESP. This ensures the | |
78 | system boots even if the first boot device fails. The ESPs are kept in sync by | |
79 | a kernel postinstall hook script `/etc/kernel/postinst.d/zz-pve-efiboot`. The | |
80 | script copies certain kernel versions and the initrd images to `EFI/proxmox/` | |
81 | on the root of each ESP and creates the appropriate config files in | |
82 | `loader/entries/proxmox-*.conf`. | |
83 | ||
84 | The following kernel versions are configured by default: | |
85 | ||
86 | * the currently running kernel | |
87 | * the version being newly installed on package updates | |
88 | * the two latest kernels | |
89 | * the latest version of each kernel series (e.g. 4.15, 5.0). | |
90 | ||
91 | The ESPs are not kept mounted during regular operation, in contrast to `grub`, | |
92 | which keeps an ESP mounted on `/boot/efi`. This helps to prevent filesystem | |
93 | corruption to the `vfat` formatted ESPs in case of a system crash, and removes | |
94 | the need to manually adapt `/etc/fstab` in case the primary boot device fails. | |
95 | ||
69055103 | 96 | [[sysboot_systemd_boot_config]] |
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97 | Configuration |
98 | ^^^^^^^^^^^^^ | |
99 | ||
100 | `systemd-boot` is configured via the file `loader/loader.conf` in the root | |
101 | directory of an EFI System Partition (ESP). See the `loader.conf(5)` manpage | |
102 | for details. | |
103 | ||
104 | Each bootloader entry is placed in a file of its own in the directory | |
105 | `loader/entries/` | |
106 | ||
107 | An example entry.conf looks like this (`/` refers to the root of the ESP): | |
108 | ||
109 | ---- | |
110 | title Proxmox | |
111 | version 5.0.15-1-pve | |
112 | options root=ZFS=rpool/ROOT/pve-1 boot=zfs | |
113 | linux /EFI/proxmox/5.0.15-1-pve/vmlinuz-5.0.15-1-pve | |
114 | initrd /EFI/proxmox/5.0.15-1-pve/initrd.img-5.0.15-1-pve | |
115 | ---- | |
116 | ||
117 | ||
118 | .Manually keeping a kernel bootable | |
119 | ||
120 | Should you wish to add a certain kernel and initrd image to the list of | |
121 | bootable kernels you need to: | |
122 | ||
123 | * create a directory on the ESP (e.g. `/EFI/personalkernel`) | |
124 | * copy the kernel and initrd image to that directory | |
125 | * create a entry for this kernel in `/loader/entries/*.conf` | |
126 | ||
127 | NOTE: do not use `/EFI/proxmox` as directory since all entries there can be | |
128 | removed by `/etc/kernel/postinst.d/zz-pve-efiboot` | |
129 | ||
130 | Example (keeping kernel 5.0.15-1-pve and copying to an ESP mounted on | |
131 | `/mnt/esp`): | |
132 | ||
133 | ---- | |
134 | mkdir /mnt/esp/EFI/preferred-kernel | |
135 | cp /boot/initrd.img-5.0.15-1-pve /boot/vmlinuz-5.0.15-1-pve /mnt/esp/EFI/preferred-kernel | |
136 | echo -n "title Preferred Kernel | |
137 | version 5.0.15-1-pve | |
138 | linux /mnt/esp/EFI/preferred-kernel/vmlinuz-5.0.15-1-pve | |
139 | initrd /mnt/esp/EFI/preferred-kernel/initrd.img-5.0.15-1-pve | |
140 | options " > /mnt/esp/loader/entries/preferred.conf | |
141 | cat /etc/kernel/cmdline >> /mnt/esp/loader/entries/preferred.conf | |
142 | ---- | |
143 | ||
0daaddbd FG |
144 | [[sysboot_systemd_boot_setup]] |
145 | .Setting up a new partition for use as synced ESP | |
146 | ||
147 | To format and initialize a partition as synced ESP, e.g., after replacing a | |
148 | failed vdev in an rpool, or when converting an existing system that pre-dates | |
149 | the sync mechanism, `pve-efiboot-tool` from `pve-kernel-helpers` can be used. | |
150 | ||
151 | WARNING: the `format` command will format the `<partition>`, make sure to pass | |
152 | in the right device/partition! | |
153 | ||
154 | For example, to format an empty partition `/dev/sda2` as ESP, run the following: | |
155 | ||
156 | ---- | |
157 | pve-efiboot-tool format /dev/sda2 | |
158 | ---- | |
159 | ||
160 | To setup an existing, unmounted ESP located on `/dev/sda2` for inclusion in | |
3fe127c7 | 161 | {pve}'s kernel update synchronization mechanism, use the following: |
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162 | |
163 | ---- | |
164 | pve-efiboot-tool init /dev/sda2 | |
165 | ---- | |
166 | ||
167 | Afterwards `/etc/kernel/pve-efiboot-uuids` should contain a new line with the | |
168 | UUID of the newly added partition. The `init` command will also automatically | |
169 | trigger a refresh of all configured ESPs. | |
62de1c14 | 170 | |
69055103 | 171 | [[sysboot_systemd_boot_refresh]] |
62de1c14 SI |
172 | .Updating the configuration on all ESPs |
173 | ||
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174 | To copy and configure all bootable kernels and keep all ESPs listed in |
175 | `/etc/kernel/pve-efiboot-uuids` in sync you just need to run `pve-efiboot-tool | |
176 | refresh`. | |
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177 | (The equivalent to running `update-grub` on Systems being booted with `grub`). |
178 | ||
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179 | This is necessary should you make changes to the kernel commandline, or want to |
180 | sync all kernels and initrds after regenerating the latter. | |
62de1c14 | 181 | |
69055103 | 182 | [[sysboot_edit_kernel_cmdline]] |
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183 | Editing the kernel commandline |
184 | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ | |
185 | ||
186 | You can modify the kernel commandline in the following places, depending on the | |
187 | bootloarder used: | |
188 | ||
189 | .Grub | |
190 | ||
191 | The kernel commandline needs to be placed in the variable | |
192 | `GRUB_CMDLINE_LINUX_DEFAULT` in the file `/etc/default/grub`. Running | |
193 | `update-grub` appends its content to all `linux` entries in | |
194 | `/boot/grub/grub.cfg`. | |
195 | ||
196 | .Systemd-boot | |
197 | ||
198 | The kernel commandline needs to be placed as line in `/etc/kernel/cmdline` | |
199 | Running `/etc/kernel/postinst.d/zz-pve-efiboot` sets it as `option` line for | |
200 | all config files in `loader/entries/proxmox-*.conf`. |