13.1 How to specify devices

The device syntax is like this:

(device[,partmap-name1part-num1[,partmap-name2part-num2[,...]]])

‘[]’ means the parameter is optional. device depends on the disk driver in use. BIOS and EFI disks use either ‘fd’ or ‘hd’ followed by a digit, like ‘fd0’, or ‘cd’. AHCI, PATA (ata), crypto, USB use the name of driver followed by a number. Memdisk and host are limited to one disk and so it’s refered just by driver name. RAID (md), ofdisk (ieee1275 and nand), LVM (lvm), LDM, virtio (vdsk) and arcdisk (arc) use intrinsic name of disk prefixed by driver name. Additionally just “nand” refers to the disk aliased as “nand”. Conflicts are solved by suffixing a number if necessarry. Commas need to be escaped. Loopback uses whatever name specified to loopback command. Hostdisk uses names specified in device.map as long as it’s of the form [fhc]d[0-9]* or hostdisk/<OS DEVICE>. For crypto and RAID (md) additionally you can use the syntax <driver name>uuid/<uuid>. For LVM additionally you can use the syntax lvmid/<volume-group-uuid>/<volume-uuid>.

(fd0)
(hd0)
(cd)
(ahci0)
(ata0)
(crypto0)
(usb0)
(cryptouuid/123456789abcdef0123456789abcdef0)
(mduuid/123456789abcdef0123456789abcdef0)
(lvm/system-root)
(lvmid/F1ikgD-2RES-306G-il9M-7iwa-4NKW-EbV1NV/eLGuCQ-L4Ka-XUgR-sjtJ-ffch-bajr-fCNfz5)
(md/myraid)
(md/0)
(ieee1275/disk2)
(ieee1275//pci@1f\,0/ide@d/disk@2)
(nand)
(memdisk)
(host)
(myloop)
(hostdisk//dev/sda)

part-num represents the partition number of device, starting from one. partname is optional but is recommended since disk may have several top-level partmaps. Specifying third and later component you can access to subpartitions.

The syntax ‘(hd0)’ represents using the entire disk (or the MBR when installing GRUB), while the syntax ‘(hd0,1)’ represents using the first partition of the disk (or the boot sector of the partition when installing GRUB).

(hd0,msdos1)
(hd0,msdos1,msdos5)
(hd0,msdos1,bsd3)
(hd0,netbsd1)
(hd0,gpt1)
(hd0,1,3)

If you enabled the network support, the special drives (protocol[,server]) are also available. Supported protocols are ‘http’ and ‘tftp’. If server is omitted, value of environment variable ‘net_default_server’ is used. Before using the network drive, you must initialize the network. See Network, for more information.

When using ‘http’ or ‘tftp’, ports other than ‘80’ can be specified using a colon (‘:’) after the address. To avoid parsing conflicts, when using IPv6 addresses with custom ports, the addresses must be enclosed with square brackets (‘[]’), as is standard practice.

(http,grub.example.com:31337)
(http,192.0.2.1:339)
(http,[2001:db8::1]:11235)

If you boot GRUB from a CD-ROM, ‘(cd)’ is available. See Making a GRUB bootable CD-ROM, for details.