Booting from a USB stick is nowadays more and more important. More and more PCs (and servers) are delivered by default without a CD/DVD drive. To install the OS of your choice, USB sticks provide you the easiest possibility. In fact, it can even work out cheaper than burning a CD or DVD that you just throw away once the version is outdated.
Mar 12, 2020 Connect the USB flash drive or other volume that you're using for the bootable installer. Make sure that it has at least 12GB of available storage and is formatted as Mac OS Extended. Open Terminal, which is in the Utilities folder of your Applications folder. May 15, 2020 A bootable installer for macOS El Capitan is a good idea even if your plan is to perform an upgrade install. Having your own copy of El Capitan on a separate device ensures that you'll always be able to install or reinstall it.It also helps in performing basic troubleshooting tasks, even if you have no connection to the internet or access to the Mac App Store.
For most Linux distributions the ISO for burning a CD/DVD is available freely on the internet. In this post I’ll assume you have already downloaded the bootable ISO image for the OS of your choice, but how to get the ISO image onto the USB stick?
The ISO file you have downloaded contains an image of the entire media. It includes all the files necessary to boot your PC/server. This image format is sadly not directly usable to copy onto the USB stick. We first need to convert the image from an ISO to a UDRW (Read/Write Universal Disk Image Format) which we can copy to the USB stick.
Some of the steps to create a bootable USB stick could be done in the GUI as well, but as some of them can’t and you have to go to the shell anyway, I decided to do all of the steps in the shell.
Convert the ISO to UDRW format
Mac OS X provides all the tools needed to convert the ISO image to UDRW. The following command will convert the ISO image to the UDRW format.
Create Bootable Usb Drive Mac Os El Capitan
You will notice that the destination_file.img from the command will create the file destination_file.img.dmg really. This is because the hdiutil program automatically adds the dmg file extension. This is not a problem as the file extension won’t affect the format of the image.
Prepare the USB stick
Check your USB stick and make a backup if there is any important data on it, as the next steps are going to delete everything on it.
To prepare the USb stick we are going to delete all the partitions on the stick and create an empty partition. To do this we need to know the device name of the USB stick. Open a terminal and execute the following command:
You will see a list of disks and partitions. The goal is to identify the USB stick in this output. Depending on your system configuration your output might look different from this one. This appears to show 3 physical discs but it does not. The /dev/disk1 is a virtual disk created because of the partition encryption (FileVault 2) I enabled in Mac OS X.
As shown in the output above, the connected USB stick is a small 2.0 GB drive with a FAT partition on it. We are now going to remove this partition in the next step. For the following steps we will need the name of the disk which in this case is “/dev/disk2”.
With the following command the data on the disk (your USB stick) will be deleted!
With this command the USB stick was re-partitioned to have 1 partition without formatting and 100% of the size of the stick. If you check it again with “diskutil list” you will see the changes already, also the USB stick will no longer be shown in the Finder.
Copy the image to the USB stick
Now we can copy the disk image we created to the USB stick. This is done via the dd(1) command. This command will copy the image to the disk (substitute the appropriate disk name for your USB stick here, as with the re-partitioning command):
The dd command does not show any output before it has finished the copy process, so be patient and wait for it to complete.
To eject the USB stick, use the above command. After this is done, the bootable USB stick is ready to be used.
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These advanced steps are primarily for system administrators and others who are familiar with the command line. You don't need a bootable installer to upgrade macOS or reinstall macOS, but it can be useful when you want to install on multiple computers without downloading the installer each time.
Download macOS
Find the appropriate download link in the upgrade instructions for each macOS version:
macOS Catalina, macOS Mojave, ormacOS High Sierra
Installers for each of these macOS versions download directly to your Applications folder as an app named Install macOS Catalina, Install macOS Mojave, or Install macOS High Sierra. If the installer opens after downloading, quit it without continuing installation. Important: To get the correct installer, download from a Mac that is using macOS Sierra 10.12.5 or later, or El Capitan 10.11.6. Enterprise administrators, please download from Apple, not a locally hosted software-update server.
OS X El Capitan
El Capitan downloads as a disk image. On a Mac that is compatible with El Capitan, open the disk image and run the installer within, named InstallMacOSX.pkg. It installs an app named Install OS X El Capitan into your Applications folder. You will create the bootable installer from this app, not from the disk image or .pkg installer. Use the 'createinstallmedia' command in Terminal
* If your Mac is using macOS Sierra or earlier, include the
--applicationpath argument, similar to the way this argument is used in the command for El Capitan.
Use the bootable installer
After creating the bootable installer, follow these steps to use it:
Make A Bootable Usb Mac OsLearn more
For more information about the
createinstallmedia command and the arguments that you can use with it, make sure that the macOS installer is in your Applications folder, then enter this path in Terminal:
Free Usb Bootable Os
Catalina:
Mojave:
Bootable Usb Mac Os Sierra
High Sierra:
Create Bootable Usb Drive Mac Os High Sierra
El Capitan:
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