Fdisk For Mac Os X

Fdisk -i -a hfs /dev/disk1. The options here are to install OS X to an external drive and boot off of that to access your main drive, or start the system in Target Disk mode, and attach it to a. Verify which disk number holds your mac partition (disk0, disk1,disk2 etc.) 4:-Assuming the MAC OS X disk (“disk1”), then type “ fdisk -e /dev/rdisk1″ and hit enter.


by Rod Smith, [email protected]

Last Web page update: 2/17/2020, referencing GPT fdisk version 1.0.5

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Fdisk For Mac Os X
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GPT fdisk (consisting of the gdisk, cgdisk,sgdisk, and fixparts programs) is a set of text-modepartitioning tools for Linux, FreeBSD, Mac OS X, and Windows. Thegdisk, cgdisk, and sgdisk programs work onGlobally Unique Identifier (GUID) Partition Table (GPT) disks, rather thanon the older (and once more common) Master Boot Record (MBR)partition tables. The fixparts program repairs certain types ofdamage to MBR disks and enables changing partition types from primary tological and vice-versa. You can learn more about fixparts on its dedicated Web page. Ifgdisk, cgdisk, and sgdisk sound interesting toyou, then read on (or skip straight to the 'Obtaining GPT fdisk' link ifyou don't need the GPT pep talk). If you don't know what a GPT is, be sureto read the first section!

FreeBSD users: The FreeBSD version of GPT fdisk can'tnormally save changes to your partition table if any partition from thedisk is mounted. If you want to modify your FreeBSD boot disk, the safestway to do so is from an emergency system or from a dual boot to another OS.Alternatively, you can type sysctl kern.geom.debugflags=16at a shell prompt to enable FreeBSD to write to active disks. Thislimitation is shared by at least some other FreeBSD partitioning tools,such as gpt and FreeBSD's fdisk. This limitation doesnot exist in the Linux, Mac OS X, or Windows versions of thesoftware.

OS X 10.11 ('El Capitan') and later users: This versionof OS X adds a feature called System Integrity Protection (SIP), or lessformally, 'rootless.' This system blocks access to certain critical aspectsof the OS and hardware by third-party programs, including GPT fdisk. Thus,GPT fdisk's capabilities are limited under OS X 10.11 or later unless SIP isdisabled. Specifically, low-level access to the system disk is forbidden, soyou cannot repartition it. Access to USB flash drives remains possible,though. Disabling SIP is covered on several Web sites, including hereand here.My rEFInd boot manager candisable SIP, as described here. Alternatively, youcan run GPT fdisk from a Linux emergency disk.

Fdisk For Mac Os X 10 11

Windows users: BIOS-mode version of Windows cannot bootfrom a GPT disk; Windows can boot from such disks only if the computer usesUnified Extensible Firmware Interface (UEFI) firmware. Versions prior toVista may not be able to read GPT disks at all. Since GPT fdiskautomatically turns MBR disks into GPT disks, you should use GPT fdisk onlyif you're positive your system can handle them. The vast majority ofcomputers sold with Windows 8 and later have UEFI firmware and so also useGPT. Consult Microsoft'sGPT FAQ for more information on Windows GPT support. If you have aBIOS-based computer and desperately need to boot from a GPT disk, consult myBIOS to UEFITransformation Web page.


  • What's a GPT?—A summary of basics about GPT
  • Working Around MBR's Limitations—A couple of ways to eek a bit more life out of MBR
  • Legacy BIOS Issues with GPT—Information on obscure issues related to BIOS/GPT coexistence
  • Why Use GPT fdisk?—Advice on when to use GPT fdisk vs. its alternatives
  • A gdisk Walkthrough—A demonstration of how to use GPT fdisk's interactive gdisk tool, which is a powerful tool for experts.
  • An cgdisk Walkthrough—A demonstration of how to use GPT fdisk's command-line cgdisk tool, which is easier to use for partitioning novices.
  • An sgdisk Walkthrough—A demonstration of how to use GPT fdisk's command-line gdisk tool, which is intended for use in scripts or by experts to do quick tasks.
  • Partitioning Advice—General suggestions on how to lay out your GPT partitions
  • Converting to or from GPT—If you want to convert an existing MBR or BSD disklabel disk to use GPT, or convert GPT to MBR, read this!
  • Wiping Out GPT Data—If you need to re-partition a GPT disk using MBR, read this first!
  • Booting from GPT—Advice on booting Linux, FreeBSD, Windows, and Mac OS X from GPT disks
  • Hybrid MBRs—Information on this non-standard, ugly, flaky, dangerous, but occasionally useful GPT variant.
  • Repairing GPT Disks—When a GPT disk's data structures are damaged, GPT fdisk can help you recover your data.
  • Obtaining GPT fdisk—How to get the program.
  • Revisions—GPT fdisk's revision history.

Man Pages

The Linux man pages for all of the GPT fdisk programs are availablehere:

Using GPT fdisk on Any Computer

At least three Linux emergency systems ship with GPT fdisk. You cancreate a bootable CD-R, boot it, and use GPT fdisk (and many other usefulLinux utilities) even on systems on which GPT fdisk doesn't compile. Thesetools are also very useful for Linux, FreeBSD, Mac OS X, Windows, and othersystems when things go wrong or when performing certain types of offlinemaintenance.

Mac Os X Update

The emergency disks I know of that include GPT fdisk are:

Note that GPT fdisk is a Linux text-mode tool, so you'll need to knowat least a minimal amount about using a Linux text-mode shell. Many basicintroductions are available on the Web.You'll need to learn only enough to do very basic tasks; I've got a GPT fdisk walkthrough that describes GPT fdiskitself. Depending on your rescue CD and how you launched it, you may findyourself at a text-mode shell when you first boot, or you may need tolocate an item called 'Terminal,' 'Shell,' 'xterm,' or something similar tostart your text-mode shell.

Additional Resources

Fdisk Mac Os X

  • GPT fdisk's Sourceforge page—The preferred download method for source code and non-Linux binaries. (For Linux binaries, see the 'Obtaining GPT fdisk' page.)
  • Intel's EFI page includes links to various EFI resources, including the EFI specifications, which include the official GPT 1.x specification. (In version 1.10, section describes GPT.) Note, however, that most PCs with EFI support use the newer UEFI 2.x (see next bullet point).
  • The UEFI 2.x specifications and tools detail UEFI 2.x, as implemented on some modern PC motherboards. The GPT structure is described in Section 5 (and especially Section 5.3) of the UEFI 2.7 specification. Note that UEFI 2.x uses the same GPT format (1.0) as described in version 1.x of the EFI specification, although the description has been clarified or expanded in a few areas. The GPT version number is unrelated to the EFI/UEFI version number.
  • 'Make the Most of Large Drives with GPT and Linux'—An informational piece on GPT I wrote for IBM developerWorks.
  • The Wikipedia entry on GPT—This has lots of useful technical information, including the most complete set of GUID partition codes I've seen in one place. (I implemented them all in gdisk, but there may be more by the time you read this.)
  • The Wikipedia entry on MBR—This has lots of useful technical information on MBR, should you want to compare it to the GPT information.
  • Apple's Technical Note TN2166—A document that provides technical details on GPT.
  • Microsoft's GPT FAQ—Go here to learn Windows-specific GPT information.
  • Microsoft's Recommended UEFI-Based Disk-Partition Configurations page provides details on how to partition a UEFI-based computer on which you want to install Windows.
  • Microsoft's MBR2GPT tool will convert a disk from MBR to GPT form, just as gdisk does. It also converts the Windows installation on the disk to boot in EFI/UEFI mode rather than the BIOS/CSM/legacy mode it had presumably been using.
  • A piece on Anandtech concerning the transition to 4096-byte sectors in hard disks.
  • Another of my IBM developerWorks articles, this time on using disks with 4096-byte sectors in Linux.
  • A page on repairing damage to GPT done by MacDrive under Windows. This page includes a simple Python utility to repair the damage, but of you can do the same thing with GPT fdisk.
  • A Web page I've written on recovering MBR disks that GNU Parted, GParted, and other libparted-based tools can't handle because of an improper extended partition definition.
  • Google's Chromium project Web page includes a page on disk formats, including information on how ChromeOS uses GPT disks.
  • My Web page on rEFInd, a boot loader project derived from the earlier rEFIt, covers this boot loader for EFI systems.
  • My Linux on UEFI: A Quick Installation Guide page provides helpful tips on how to install Linux on EFI-based systems.

If you have problems with or comments about this web page, pleasee-mail me at [email protected] Thanks.

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