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Groups > linux.debian.user > #201503 > unrolled thread
| Started by | D&P Dimov <lddimov@yahoo.com> |
|---|---|
| First post | 2018-10-21 15:30 +0200 |
| Last post | 2018-10-23 04:30 +0200 |
| Articles | 14 — 6 participants |
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Won't boot if /, home, swap are encrypted D&P Dimov <lddimov@yahoo.com> - 2018-10-21 15:30 +0200
Re: Won't boot if /, home, swap are encrypted Matthew Crews <mailinglists@mattcrews.com> - 2018-10-21 15:40 +0200
Re: Won't boot if /, home, swap are encrypted Roberto C. Sánchez <roberto@debian.org> - 2018-10-21 19:40 +0200
Re: Won't boot if /, home, swap are encrypted D&P Dimov <lddimov@yahoo.com> - 2018-10-21 19:50 +0200
Re: Won't boot if /, home, swap are encrypted Matthew Crews <mailinglists@mattcrews.com> - 2018-10-22 02:10 +0200
Re: Won't boot if /, home, swap are encrypted D&P Dimov <lddimov@yahoo.com> - 2018-10-22 04:20 +0200
Re: Won't boot if /, home, swap are encrypted David Wright <deblis@lionunicorn.co.uk> - 2018-10-22 07:10 +0200
Re: Won't boot if /, home, swap are encrypted David Wright <deblis@lionunicorn.co.uk> - 2018-10-22 06:00 +0200
Re: Won't boot if /, home, swap are encrypted Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-10-22 14:50 +0200
Re: Won't boot if /, home, swap are encrypted David Wright <deblis@lionunicorn.co.uk> - 2018-10-22 18:00 +0200
Re: Won't boot if /, home, swap are encrypted Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-10-22 19:50 +0200
Re: Won't boot if /, home, swap are encrypted Joe <joe@jretrading.com> - 2018-10-22 19:50 +0200
Re: Won't boot if /, home, swap are encrypted Pascal Hambourg <pascal@plouf.fr.eu.org> - 2018-10-22 20:10 +0200
Re: Won't boot if /, home, swap are encrypted David Wright <deblis@lionunicorn.co.uk> - 2018-10-23 04:30 +0200
| From | D&P Dimov <lddimov@yahoo.com> |
|---|---|
| Date | 2018-10-21 15:30 +0200 |
| Subject | Won't boot if /, home, swap are encrypted |
| Message-ID | <wLlXP-4B3-5@gated-at.bofh.it> |
I did a new install of latest Debian 9.5 stable on a new Dell laptop. Debian is the only OS there now. If I encrypt /, home, and swap, it won't boot after install. If I leave them unencrypted, it boots fine. What am I missing? Thanks!
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| From | Matthew Crews <mailinglists@mattcrews.com> |
|---|---|
| Date | 2018-10-21 15:40 +0200 |
| Message-ID | <wLm7w-4Eb-3@gated-at.bofh.it> |
| In reply to | #201503 |
On 10/21/18 6:25 AM, D&P Dimov wrote:
> I did a new install of latest Debian 9.5 stable on a new Dell laptop. Debian is the only OS there now. If I encrypt /, home, and swap, it won't boot after install. If I leave them unencrypted, it boots fine. What am I missing?
> Thanks!
>
Did you remember to make an unencrypted /boot partition? The Debian
installer does not support encrypted /boot partition, you will need to
leave it unencrypted.
For example, see my current partition table:
matthew@matt-tower:~$ lsblk
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 465.8G 0 disk
├─sda1 8:1 0 953.7M 0 part /boot
├─sda2 8:2 0 1K 0 part
└─sda5 8:5 0 464.8G 0 part
└─sda5_crypt 254:0 0 464.8G 0 crypt
├─root--swap-root 254:1 0 447G 0 lvm /
└─root--swap-swap 254:2 0 17.8G 0 lvm [SWAP]
sdb 8:16 0 931.5G 0 disk
└─sdb1 8:17 0 931.5G 0 part
└─sdb1_crypt 254:3 0 931.5G 0 crypt
└─home-home 254:4 0 931.5G 0 lvm /home
/boot is its own unencrypted partition, root and swap are in a LUKS
encryption, and /home is on its own hard disk (and also LUKS encrypted)
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| From | Roberto C. Sánchez <roberto@debian.org> |
|---|---|
| Date | 2018-10-21 19:40 +0200 |
| Message-ID | <wLpRL-6S7-5@gated-at.bofh.it> |
| In reply to | #201503 |
On Sun, Oct 21, 2018 at 01:25:09PM +0000, D&P Dimov wrote: > I did a new install of latest Debian 9.5 stable on a new Dell laptop. Debian is the only OS there now. If I encrypt /, home, and swap, it won't boot after install. If I leave them unencrypted, it boots fine. What am I missing? > Thanks! > It will be much easier to help you if you could post the complete output of the boot sequence up to the failure. If that is not possible, then perhaps the last screenful or last few lines. Or even a photograph of the screen showing where the boot sequence is stuck. Regards, -Roberto -- Roberto C. Sánchez
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| From | D&P Dimov <lddimov@yahoo.com> |
|---|---|
| Date | 2018-10-21 19:50 +0200 |
| Message-ID | <wLq1r-6Vq-5@gated-at.bofh.it> |
| In reply to | #201516 |
[Multipart message — attachments visible in raw view] — view raw
Hi Roberto,
It was telling me that it was not finding anything to boot from. But I'm good now, I got it to boot and sent a message to the list a little while ago. Though I'm not sure why did it now but didn't do it earlier, after I tried a dozen different times...
On Sunday, October 21, 2018, 1:31:08 PM EDT, Roberto C. Sánchez <roberto@debian.org> wrote:
On Sun, Oct 21, 2018 at 01:25:09PM +0000, D&P Dimov wrote:
> I did a new install of latest Debian 9.5 stable on a new Dell laptop. Debian is the only OS there now. If I encrypt /, home, and swap, it won't boot after install. If I leave them unencrypted, it boots fine. What am I missing?
> Thanks!
>
It will be much easier to help you if you could post the complete output
of the boot sequence up to the failure. If that is not possible, then
perhaps the last screenful or last few lines. Or even a photograph of
the screen showing where the boot sequence is stuck.
Regards,
-Roberto
--
Roberto C. Sánchez
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| From | Matthew Crews <mailinglists@mattcrews.com> |
|---|---|
| Date | 2018-10-22 02:10 +0200 |
| Message-ID | <wLvXc-2hm-3@gated-at.bofh.it> |
| In reply to | #201516 |
[Multipart message — attachments visible in raw view] — view raw
‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Sunday, October 21, 2018 10:29 AM, Roberto C. Sánchez <roberto@debian.org> wrote:
> On Sun, Oct 21, 2018 at 01:25:09PM +0000, D&P Dimov wrote:
>
> > I did a new install of latest Debian 9.5 stable on a new Dell laptop. Debian is the only OS there now. If I encrypt /, home, and swap, it won't boot after install. If I leave them unencrypted, it boots fine. What am I missing?
> > Thanks!
>
> It will be much easier to help you if you could post the complete output
> of the boot sequence up to the failure. If that is not possible, then
> perhaps the last screenful or last few lines. Or even a photograph of
> the screen showing where the boot sequence is stuck.
To satisfy my curiosity, I fired up a VM and in the VM used the Debian installer to automatically partition for an encrypted install, with separate /, /home, and /swap. It made a 1MB blank partition, 512MiB /boot/efi partition flagged as bootable, 244MiB /boot partition, and allocated the rest of the disk to the LUKS container. In the LUKS container contained /, /home, and /swap. See the attached picture.
After installation was complete, here is the output of lsblk.
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 20G 0 disk
├─sda1 8:1 0 512M 0 part /boot/efi
├─sda2 8:2 0 244M 0 part /boot
└─sda3 8:3 0 19.3G 0 part
└─sda3_crypt 254:0 0 19.3G 0 crypt
├─debian--vm--vg-root 254:1 0 6.4G 0 lvm /
├─debian--vm--vg-swap_1 254:2 0 2G 0 lvm [SWAP]
└─debian--vm--vg-home 254:3 0 10.9G 0 lvm /home
sr0 11:0 1 55.3M 0 rom
It seems the best practice is:
1MB blank partition at the beginning of the drive
512MB EFI partition (or larger) mounted at /boot/efi, flagged as bootable
256MB /boot partition (or larger as desired), NOT flagged as bootable.
Then the rest of the drive partitioned as desired (ie a LUKS container)
If all of these conditions are met, then encrypted boot with EFI *should* work correctly.
So I'm at a loss, D&P Dimov, as to why you had difficulty. You said it was a config in your BIOS that you needed to change?
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| From | D&P Dimov <lddimov@yahoo.com> |
|---|---|
| Date | 2018-10-22 04:20 +0200 |
| Message-ID | <wLxYZ-3vd-1@gated-at.bofh.it> |
| In reply to | #201520 |
[Multipart message — attachments visible in raw view] — view raw
Dear Mathew,
Thank you for looking into this further.
I did not have to change anything in the BIOS - it was fine all along. Here are some differences from what you have and some of my issues:
1. I did not have a 1MB free space. I didn't know that I had to leave that free space. The Debian installation instructions regarding partitioning (https://www.debian.org/releases/stretch/amd64/ch06s03.html.en#di-partition) show a table at the end of "6.3.3.2. Guided Partitioning" (which was achieved with Manual Partitioning, as per the table caption below it) that has free space, but there is no indication that it is required. The next section on that same webpage covers manual partitioning and doesn't indicate that free space requirement either. At the end, I installed and booted successfully into Debian without this free space.
2. The table from the debian instructions (referenced above) does not show a bootable EFI, only a bootable /boot. Though the text does specify "If you have booted in EFI mode then within the guided partitioningsetup there will be an additional partition, formatted as a FAT32bootable filesystem, for the EFI boot loader." I think that the instructions can be improved by showing an EFI partition like in the screenshot you sent. I think I also kept forcing the /boot to have a "Boot Flag: On". It seems counter intuitive, but apparently the /boot partition must not have a bootable flag - also something that maybe should be clarified in the instructions.
3. You keep referring to the EFI partition as being mounted on "/boot/efi", which I could do by manually typing this mount point, but this was not acceptable to the installer - it came back telling me that I don't have an EFI. So instead, the EFI needs to be selected from the menu, where it is listed under swap as "EFI System Partition".
Next time I install Debian on another machine (should be soon), I think I'll do graphic install so I can take screenshots along the way and make a set of instructions for less experienced users like me. Encrypting the /, home, and swap was also not straight forward to me from the instructions - two videos by Rex Kneisley is what helped me figure out how to do it. (Though the encryption part was not the cause of not being able to boot into the newly installed system.) So I'll be sure to include screenshots of these steps as well. Any ideas as to where may be a good place to post such instructions and screenshots? Do you think anyone would be interested in including them with the official installation guide?
Thanks!
On Sunday, October 21, 2018, 8:06:28 PM EDT, Matthew Crews <mailinglists@mattcrews.com> wrote:
‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Sunday, October 21, 2018 10:29 AM, Roberto C. Sánchez <roberto@debian.org> wrote:
> On Sun, Oct 21, 2018 at 01:25:09PM +0000, D&P Dimov wrote:
>
> > I did a new install of latest Debian 9.5 stable on a new Dell laptop. Debian is the only OS there now. If I encrypt /, home, and swap, it won't boot after install. If I leave them unencrypted, it boots fine. What am I missing?
> > Thanks!
>
> It will be much easier to help you if you could post the complete output
> of the boot sequence up to the failure. If that is not possible, then
> perhaps the last screenful or last few lines. Or even a photograph of
> the screen showing where the boot sequence is stuck.
To satisfy my curiosity, I fired up a VM and in the VM used the Debian installer to automatically partition for an encrypted install, with separate /, /home, and /swap. It made a 1MB blank partition, 512MiB /boot/efi partition flagged as bootable, 244MiB /boot partition, and allocated the rest of the disk to the LUKS container. In the LUKS container contained /, /home, and /swap. See the attached picture.
After installation was complete, here is the output of lsblk.
NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT
sda 8:0 0 20G 0 disk
├─sda1 8:1 0 512M 0 part /boot/efi
├─sda2 8:2 0 244M 0 part /boot
└─sda3 8:3 0 19.3G 0 part
└─sda3_crypt 254:0 0 19.3G 0 crypt
├─debian--vm--vg-root 254:1 0 6.4G 0 lvm /
├─debian--vm--vg-swap_1 254:2 0 2G 0 lvm [SWAP]
└─debian--vm--vg-home 254:3 0 10.9G 0 lvm /home
sr0 11:0 1 55.3M 0 rom
It seems the best practice is:
1MB blank partition at the beginning of the drive
512MB EFI partition (or larger) mounted at /boot/efi, flagged as bootable
256MB /boot partition (or larger as desired), NOT flagged as bootable.
Then the rest of the drive partitioned as desired (ie a LUKS container)
If all of these conditions are met, then encrypted boot with EFI *should* work correctly.
So I'm at a loss, D&P Dimov, as to why you had difficulty. You said it was a config in your BIOS that you needed to change?
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| From | David Wright <deblis@lionunicorn.co.uk> |
|---|---|
| Date | 2018-10-22 07:10 +0200 |
| Message-ID | <wLADv-5aD-1@gated-at.bofh.it> |
| In reply to | #201522 |
On Mon 22 Oct 2018 at 02:06:05 (+0000), D&P Dimov wrote: > Dear Mathew, > Thank you for looking into this further. > I did not have to change anything in the BIOS - it was fine all along. Here are some differences from what you have and some of my issues: > 1. I did not have a 1MB free space. I didn't know that I had to leave that free space. The Debian installation instructions regarding partitioning (https://www.debian.org/releases/stretch/amd64/ch06s03.html.en#di-partition) show a table at the end of "6.3.3.2. Guided Partitioning" (which was achieved with Manual Partitioning, as per the table caption below it) that has free space, but there is no indication that it is required. The next section on that same webpage covers manual partitioning and doesn't indicate that free space requirement either. At the end, I installed and booted successfully into Debian without this free space. That's a diagram showing some fairly old disks. From the second column, you can see that they're both MBR partitioned. The first partition likely starts at sector 63 and they'll show no free space in the installer. > 2. The table from the debian instructions (referenced above) does not show a bootable EFI, only a bootable /boot. Though the text does specify "If you have booted in EFI mode then within the guided partitioningsetup there will be an additional partition, formatted as a FAT32bootable filesystem, for the EFI boot loader." I think that the instructions can be improved by showing an EFI partition like in the screenshot you sent. I think I also kept forcing the /boot to have a "Boot Flag: On". It seems counter intuitive, but apparently the /boot partition must not have a bootable flag - also something that maybe should be clarified in the instructions. I don't know how an ESP is displayed on an MBR disk. I would assume from the text that partition 2 on disk 2 is meant to represent one as it has a FAT filesystem and is of a suitable size. Without knowing more about the motherboard running the computer (yours and the one in the manual), it's hard to be specific about exactly what will successfully boot. The system shown could be booting in BIOS mode, in which case MBR disk 1 has a bootable partition which some BIOSes allegedly require. OTOH it could be booting in EFI mode in which case the firmware might find the required ESP on disk 2. But whi knows. > 3. You keep referring to the EFI partition as being mounted on "/boot/efi", which I could do by manually typing this mount point, but this was not acceptable to the installer - it came back telling me that I don't have an EFI. So instead, the EFI needs to be selected from the menu, where it is listed under swap as "EFI System Partition". AIUI the ESP is normally mounted on /boot/efi when the installed system is running, as that's where grub-install expects to find it. But during installation, it's just a separate partition that you either create yourself or let the installer create for you. I thought the installer handles the ESP itself at the step "Install the GRUB boot loader on a hard disk". > Next time I install Debian on another machine (should be soon), I think I'll do graphic install so I can take screenshots along the way and make a set of instructions for less experienced users like me. Encrypting the /, home, and swap was also not straight forward to me from the instructions - two videos by Rex Kneisley is what helped me figure out how to do it. (Though the encryption part was not the cause of not being able to boot into the newly installed system.) So I'll be sure to include screenshots of these steps as well. Any ideas as to where may be a good place to post such instructions and screenshots? Do you think anyone would be interested in including them with the official installation guide? Well, it certainly looks as if they could do with an update. Cheers, David.
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| From | David Wright <deblis@lionunicorn.co.uk> |
|---|---|
| Date | 2018-10-22 06:00 +0200 |
| Message-ID | <wLzxL-4fr-5@gated-at.bofh.it> |
| In reply to | #201520 |
On Mon 22 Oct 2018 at 00:05:45 (+0000), Matthew Crews wrote: > ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐ > On Sunday, October 21, 2018 10:29 AM, Roberto C. Sánchez <roberto@debian.org> wrote: > > > On Sun, Oct 21, 2018 at 01:25:09PM +0000, D&P Dimov wrote: > > > > > I did a new install of latest Debian 9.5 stable on a new Dell laptop. Debian is the only OS there now. If I encrypt /, home, and swap, it won't boot after install. If I leave them unencrypted, it boots fine. What am I missing? > > > Thanks! > > > > It will be much easier to help you if you could post the complete output > > of the boot sequence up to the failure. If that is not possible, then > > perhaps the last screenful or last few lines. Or even a photograph of > > the screen showing where the boot sequence is stuck. > > To satisfy my curiosity, I fired up a VM and in the VM used the Debian installer to automatically partition for an encrypted install, with separate /, /home, and /swap. It made a 1MB blank partition, 512MiB /boot/efi partition flagged as bootable, 244MiB /boot partition, and allocated the rest of the disk to the LUKS container. In the LUKS container contained /, /home, and /swap. See the attached picture. It needs to be pointed out that the 1MB FREE SPACE at the start of the disk (and the one at the end) is not a blank partition: it is free space. > After installation was complete, here is the output of lsblk. > > NAME MAJ:MIN RM SIZE RO TYPE MOUNTPOINT > sda 8:0 0 20G 0 disk > ├─sda1 8:1 0 512M 0 part /boot/efi > ├─sda2 8:2 0 244M 0 part /boot > └─sda3 8:3 0 19.3G 0 part > └─sda3_crypt 254:0 0 19.3G 0 crypt > ├─debian--vm--vg-root 254:1 0 6.4G 0 lvm / > ├─debian--vm--vg-swap_1 254:2 0 2G 0 lvm [SWAP] > └─debian--vm--vg-home 254:3 0 10.9G 0 lvm /home > sr0 11:0 1 55.3M 0 rom > > > It seems the best practice is: > 1MB blank partition at the beginning of the drive Noted above. This is to give you partition alignment of 1MiB for efficiency. For GPT disks like this, I also add a 3MiB partition (giving me 4MiB alignment) set to "BIOS boot" which, like it says, allows it to be booted in legacy mode if ever required. > 512MB EFI partition (or larger) mounted at /boot/efi, flagged as bootable > 256MB /boot partition (or larger as desired), NOT flagged as bootable. > Then the rest of the drive partitioned as desired (ie a LUKS container) > > If all of these conditions are met, then encrypted boot with EFI *should* work correctly. > > So I'm at a loss, D&P Dimov, as to why you had difficulty. You said it was a config in your BIOS that you needed to change? Cheers, David.
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| From | Pascal Hambourg <pascal@plouf.fr.eu.org> |
|---|---|
| Date | 2018-10-22 14:50 +0200 |
| Message-ID | <wLHOF-OM-5@gated-at.bofh.it> |
| In reply to | #201523 |
Le 22/10/2018 à 05:50, David Wright a écrit : > > Noted above. This is to give you partition alignment of 1MiB for > efficiency. For GPT disks like this, I also add a 3MiB partition > (giving me 4MiB alignment) set to "BIOS boot" which, like it says, > allows it to be booted in legacy mode if ever required. Why do you need 4 MiB alignment ?
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| From | David Wright <deblis@lionunicorn.co.uk> |
|---|---|
| Date | 2018-10-22 18:00 +0200 |
| Message-ID | <wLKMx-2x6-3@gated-at.bofh.it> |
| In reply to | #201526 |
On Mon 22 Oct 2018 at 14:42:09 (+0200), Pascal Hambourg wrote: > Le 22/10/2018 à 05:50, David Wright a écrit : > > > > Noted above. This is to give you partition alignment of 1MiB for > > efficiency. For GPT disks like this, I also add a 3MiB partition > > (giving me 4MiB alignment) set to "BIOS boot" which, like it says, > > allows it to be booted in legacy mode if ever required. > > Why do you need 4 MiB alignment ? As you probably know, I don't. Is there any harm in always rounding up? I'm just generous to Grub and its ilk. When you read posts about partitioning, you realise there are some really stingy people out there. They would probably be calculating a size that squeezes it into the space before 1MiB. Cheers, David.
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| From | Pascal Hambourg <pascal@plouf.fr.eu.org> |
|---|---|
| Date | 2018-10-22 19:50 +0200 |
| Message-ID | <wLMuZ-3Ao-1@gated-at.bofh.it> |
| In reply to | #201531 |
Le 22/10/2018 à 17:49, David Wright a écrit : > On Mon 22 Oct 2018 at 14:42:09 (+0200), Pascal Hambourg wrote: >> Le 22/10/2018 à 05:50, David Wright a écrit : >>> >>> Noted above. This is to give you partition alignment of 1MiB for >>> efficiency. For GPT disks like this, I also add a 3MiB partition >>> (giving me 4MiB alignment) set to "BIOS boot" which, like it says, >>> allows it to be booted in legacy mode if ever required. >> >> Why do you need 4 MiB alignment ? > > As you probably know, I don't. No, I didn't know, so I was curious. You may use an SSD with an uncommon 4 MiB erase block size. Less than one hour after I posted the question, I read a post from someone who considered converting partitions into LVM logical volumes without moving data and was fortunate they used 4 MiB alignment, as LVM uses 4 MiB blocks (extents) by default. > Is there any harm in always rounding up? It wastes space. > I'm just generous to Grub and its ilk. GRUB does not even need a MiB BIOS boot partition. AFAICS, the biggest generated core image embedding all required drivers fits into 128 KiB. > When you read posts about > partitioning, you realise there are some really stingy people out > there. They would probably be calculating a size that squeezes it into > the space before 1MiB. This is what I do when converting a disk from DOS/MBR to GPT. There is plenty of space for a BIOS boot partition between the GPT partition table and 1 MiB, and the BIOS boot partition does not need to be aligned (no write performance issue).
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| From | Joe <joe@jretrading.com> |
|---|---|
| Date | 2018-10-22 19:50 +0200 |
| Message-ID | <wLMv0-3Ao-5@gated-at.bofh.it> |
| In reply to | #201533 |
On Mon, 22 Oct 2018 19:41:09 +0200 Pascal Hambourg <pascal@plouf.fr.eu.org> wrote: > > GRUB does not even need a MiB BIOS boot partition. AFAICS, the > biggest generated core image embedding all required drivers fits into > 128 KiB. But all kernels get upgraded, and many people like to keep a spare one around, just in case... -- Joe
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| From | Pascal Hambourg <pascal@plouf.fr.eu.org> |
|---|---|
| Date | 2018-10-22 20:10 +0200 |
| Message-ID | <wLMOm-3Wk-11@gated-at.bofh.it> |
| In reply to | #201534 |
Le 22/10/2018 à 19:48, Joe a écrit : > On Mon, 22 Oct 2018 19:41:09 +0200 > Pascal Hambourg <pascal@plouf.fr.eu.org> wrote: > > >> >> GRUB does not even need a MiB BIOS boot partition. AFAICS, the >> biggest generated core image embedding all required drivers fits into >> 128 KiB. > > But all kernels get upgraded, and many people like to keep a spare one > around, just in case... A BIOS boot partition is not to be confused with a /boot partition. It only serves to store a (one single) GRUB core image, not Linux kernel images.
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| From | David Wright <deblis@lionunicorn.co.uk> |
|---|---|
| Date | 2018-10-23 04:30 +0200 |
| Message-ID | <wLUCd-8X-5@gated-at.bofh.it> |
| In reply to | #201533 |
On Mon 22 Oct 2018 at 19:41:09 (+0200), Pascal Hambourg wrote: > Le 22/10/2018 à 17:49, David Wright a écrit : > > On Mon 22 Oct 2018 at 14:42:09 (+0200), Pascal Hambourg wrote: > > > Le 22/10/2018 à 05:50, David Wright a écrit : > > > > > > > > Noted above. This is to give you partition alignment of 1MiB for > > > > efficiency. For GPT disks like this, I also add a 3MiB partition > > > > (giving me 4MiB alignment) set to "BIOS boot" which, like it says, > > > > allows it to be booted in legacy mode if ever required. > > > > > > Why do you need 4 MiB alignment ? > > > > As you probably know, I don't. > > No, I didn't know, so I was curious. You may use an SSD with an > uncommon 4 MiB erase block size. Less than one hour after I posted the > question, I read a post from someone who considered converting > partitions into LVM logical volumes without moving data and was > fortunate they used 4 MiB alignment, as LVM uses 4 MiB blocks > (extents) by default. Sorry to make the assumption. For me, disks are spinning rust and SSDs are something for the future. Perhaps. If I'm fortunate. > > Is there any harm in always rounding up? > > It wastes space. > > > I'm just generous to Grub and its ilk. > > GRUB does not even need a MiB BIOS boot partition. AFAICS, the biggest > generated core image embedding all required drivers fits into 128 KiB. > > > When you read posts about > > partitioning, you realise there are some really stingy people out > > there. They would probably be calculating a size that squeezes it into > > the space before 1MiB. > > This is what I do when converting a disk from DOS/MBR to GPT. There is > plenty of space for a BIOS boot partition between the GPT partition > table and 1 MiB, and the BIOS boot partition does not need to be > aligned (no write performance issue). The ones I've converted were old/relatively small (≤2TB) and had the first partition starting at the traditional 63, so I'm repartitioning from scratch anyway. But I can't get worked up over the odd MB. I've seen big disks where the first partition starts at 2048 which is 8MiB for 4K sector size. Cheers, David.
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