Great information, Michael. Thank you! Jeff -- Secured with Tuta Mail: https://tuta.com/free-email
Oct 2, 2026, 23:51 by [email protected]: > [email protected] (Jeff) writes: > > >I've been reading the documentation and doing searches, and the impression = > >that I get is that one needs to use entirely different tools to work with M= > >BR vs GPT partitions, and that most of the documentation is specific to MBR= > >. Is this true? > > > The distinction is not about MBR vs GPT. > > > NetBSD uses two partitioning schemes: > > 1. BSD disklabel (e.g. wd0a, wd0b, wd0c, ...) > 2. Wedges (e.g. dk0, dk1, dk2, ...) > > The BSD disklabel is limited to 32bit block numbers, for regular disks > (with 512 byte sectors) that limits disk size to 2TB. The disklabel > is usually stored on the disk but some architectures may use a virtual > disklabel that is generated from other information. > > With wedges, every partition gets its own unit number, there is nothing > like e.g. "dk0a". Wedges are usually generated from other information, > the generic kernel supports GPT and Apple (MacOS) partition tables, > but there are other options too. > > > By default MBR isn't used anywhere, but with MBR you would use BSD disklabel > and with GPT you would use wedges auto-generated from the GPT. > > MBR vs. GPT is more relevant for booting as e.g. a PC BIOS or UEFI firmware > support either. > > > > >Based on advice I got elsewhere, I would like to put an ext2 filesystem on = > >an existing partition that I can share between NetBSD and Gentoo on a dual = > >boot system. The advice was to create the filesystem from in NetBSD. > > That's because NetBSD supports only part of the ext2/ext3/ext4 filesystems > and creating the filesytem on NetBSD is the easiest way to have something > understood by both systems. > > > > >- How do I learn what NetBSD calls the partition that I want to work with.= > >=C2=A0 For instance, if "fdisk -l" in Linux tells me that it's /dev/sda4, w= > >hat command can I run in NetBSD to find out what NetBSD calls it? > > It may not even be visible. > > A 'sda' device on Linux probably corresponds to a 'wd0' device on NetBSD, > 'sdb' would be 'wd1', etc.. but that depends on the exact hardware. > > > If you are using MBR partitioning, then: > > Linux uses MBR partitions directly, so you use /dev/sda1, /dev/sda2, etc > for the partitions. > > On NetBSD you use the BSD disklabel, you have to add an entry for the > MBR partition to the disklabel with the right offset, size and type. This > can be done manually with the disklabel program, or you use the mbrlabel > program to assist. The disklabel partitioned are named 'a' to 'p' (with > 'a' to 'd' having special meanings). The name is then e.g. /dev/wd0e if > you use the slot for partition 'e' in the disklabel. But that partition > letter is something you assign in the disk label, it is independent of > the partition number used by Linux. > > > If you are using GPT partitioning, then: > > Linux uses GPT partitions directly and something like /dev/sda3 would > be the third partition on the first disk. > > NetBSD uses wedge units 'dk0', 'dk1', etc but there is no 1:1 relationship > and it's even possible (but unlikely for internal disks) that the unit numbers > change from boot to boot. You can use e.g. 'dkctl wd0 listwedges' to show > all wedge units that are located on disk 'wd0' (i.e. the first SATA disk). > > Since wedge units can change from boot to boot, most tools dealing with > disks have another way to access them. Each wedge has a unique name, > that is taken from e.g. the GPT and the tools interpret the syntax > NAME=<partitonname> and translate it into the right /dev/dk123 unit > for you. > > E.g.: > > % dkctl wd1 listwedges > /dev/rwd1: 6 wedges: > dk1: gossam-efi, 206814 blocks at 34, type: msdos > dk2: gossam-root, 819200 blocks at 206848, type: ffs > dk3: gossam-swap, 134217728 blocks at 1026048, type: swap > dk4: gossam-usr, 67108864 blocks at 135243776, type: ffs > dk5: gossam-var, 16777216 blocks at 202352640, type: ffs > dk6: gossam-home, 3687899136 blocks at 219129856, type: ffs > > and an entry in /etc/fstab would look like: > > NAME=gossam-usr /usr ffs rw,log 1 2 > > N.B. If the GPT doesn't contain such names, there is always a UUID that is > used as a default name. > > > > >- Once I know what identifier I should use in NetBSD to refer to the partit= > >ion (or slice? wedge?), what tool(s) do I use to create the ext2 filesystem= > >> on it? >> > > The tool is named newfs_ext2fs. > > > >- Are there any other steps or tools needed that would not occur to me, com= > >ing from Linux? > > The only missing part might the 'gpt' tool that lets you create or edit the > GPT > stored on a disk. >
