Or if existing OS uses MBR and it is to be preserved.
That goes without saying.
It does not. It works fine with GPT, both in BIOS and UEFI mode.
I know about win10's diskmgmt.msc... it was OK stuff, very limited in features. And win11's version left me frustrated, because I could not reliably use it - the utility hangs from time to time, and I suspect that's because I mapped some samba shares to the middle letters of the English alphabet (and those shares are intentionally, by design, not always available, which is OK for my scenario at this time).
This goes to OP too: you can always create a VM and test it there. Many times you can easily switch between UEFI/legacy so you can test things out. And you can keep snapshots in case you do something wrong.
root@:~ # gpart show
=> 34 419430333 nvd0 GPT (200G)
34 2014 - free - (1.0M)
2048 921600 1 ms-recovery (450M)
923648 202752 2 efi (99M)
1126400 32768 3 ms-reserved (16M)
1159168 144900063 4 ms-basic-data (69G)
146059231 104857601 - free - (50G) ; ignore this gap, it was a d:\ drive
250916832 159383552 6 freebsd-ufs (76G)
410300384 8388608 7 freebsd-swap (4.0G)
418688992 741375 - free - (362M)root@:~ # find /boot/efi
/boot/efi
/boot/efi/EFI
/boot/efi/EFI/Microsoft
/boot/efi/EFI/Microsoft/Boot
/boot/efi/EFI/Microsoft/Boot/BCD
/boot/efi/EFI/Microsoft/Boot/BCD.LOG
....
/boot/efi/EFI/Boot
/boot/efi/EFI/Boot/bootx64.efi
/boot/efi/EFI/freebsd
/boot/efi/EFI/freebsd/loader.efiroot@:~ # efibootmgr
Boot to FW : false
BootCurrent: 0005
Timeout : 2 seconds
BootOrder : 0005, 0004, 0001, 0002, 0003, 0000
+Boot0005* FreeBSD
Boot0004* Windows Boot Manager
Boot0001* EFI VMware Virtual SATA CDROM Drive (1.0)
Boot0002* EFI Network
Boot0003* EFI Internal Shell (Unsupported option)
Boot0000* EFI VMware Virtual NVME Namespace (NSID 1)
root@:~ #efibootmgr -o 0000,0005. I rebooted and I'm in Windows. I would have to google around what native tool Windows has to manage EFI entries. I'm assuming you can do it somehow.I mean that FreeBSD's boot manager works in any configuration you need or want it to work in. That can be MBR, or GPT. It could be BIOS or UEFI, both paired with either partitioning scheme. I'd highly recommend sticking to GPT on new installs unless you have a really good reason not to (MBR is severely limited...), and if you're doing a dual boot setup, Windows is so fragile that you can't easily swap it and keep an install working. For anything in the last decade, UEFI+GPT is almost a sure thing.
I'm still not sure what you mean by 'FreeBSD's Boot manager'.... I always associate the term with boot0cfg().
Apologies. I was not aware of boot(8), gptboot(8) and gptzfsboot(8) being boot managers....
I'm not providing information, merely relating my personal experience. I'm certainly not uptodate on Windows and don't wish to be. I have a lot of old laptop disks which inevitably have some version of Windows installed, but looking through them yesterday I couldn't find any installed on a GPT disk.
This sounds interesting although I'm not entirely clear about how you do this. I don't generally use bsdinstall these days but use an existing installation to format and partition a new device creating a freebsd-boot and freebsd-ufs partition, then simply extract the kernel and base txz onto the freebsd-ufs partition and reboot. The new device generally boots up straightaway, stopping at the mountroot prompt, but all you need to do is enter ufs:/dev/da1p2 (adjusted for the relevant device) and it carries on to the login prompt.
i have a hp thin client boxwhich will not boot gpt without efi. it wont even try, just display an error. mbr or gpt + efi works
By "without efi" you mean that disk using GPT requires EFI partition to be preset otherwise client won't attempt to boot ?
In Chapter 15. The FreeBSD Booting Process, at 15.2.1. The Boot Manager, the Handbook says:
FreeBSD's boot manager requires MBR
Chapter 15. The FreeBSD Booting Process
An introduction to the FreeBSD Booting Process, demonstrates how to customize the FreeBSD boot process, including everything that happens until the FreeBSD kernel has started, probed for devices, and started init
If you have GPT you would probably need to install your own bootloader such as GRUB, which simply adds a number of hurdles into the mix.
"By default, FreeBSD uses the boot0 boot manager.", has not the most general meaning that it may suggest. It is meant for (only) the MBR partitioning scheme specifically; it is easily interpreted otherwise. The Handbook only explains in detail the boot process for a MBR partitioning scheme in combination with UFS. The chain of steps in the boot process varies depending on the partitioning scheme, the filesystem and (CPU) architecture.
boot0cfg implies, it can act only on boot0; note that boot0 is the actual MBR. With MBR /boot/boot0 is used at STAGE 0 of the boot process; with GPT /boot/pmbr is used instead.boot0 boot manager). In that way you could brand other individual parts of FreeBSD as "boot managers" as well. On the other hand, looking at it from a broader view, you can say that all these parts together represent "the FreeBSD boot manager". It depends more or less on your point of view.