MacBook Air Sierra install fail: Couldn't mount base system dmg! (error code 60)

Question

I have a MacBook Air and I tried running a Sierra install USB on it. Everything went smoothly but it showed "An error occurred while preparing the installation."

So I looked that up on the internet and tried the following suggestions:

• setting the date and time
• turning the Wi-Fi on
• resetting the NVRAM.

Regardless I kept getting the same error. I tried opening the log and showing all logs. See log below:

Aug 17 21:41:51 MacBook-Air InstallAssistant[590]: Hardware: MacBookAir3,1 @ 1.40 GHz (x 2), 2048 MB RAM
Aug 17 21:41:51 MacBook-Air InstallAssistant[590]: Running OS Build: Mac OS X 10.12.6 (16G29)
Aug 17 21:41:51 MacBook-Air InstallAssistant[590]: Env: DYLD_NO_FIX_PREBINDING=1
Aug 17 21:41:51 MacBook-Air InstallAssistant[590]: Env: PATH=/usr/bin:/bin:/usr/sbin:/sbin
Aug 17 21:41:51 MacBook-Air InstallAssistant[590]: Env: PWD=/
Aug 17 21:41:51 MacBook-Air InstallAssistant[590]: Env: XPC_FLAGS=0x0
Aug 17 21:41:51 MacBook-Air InstallAssistant[590]: Env: XPC_SERVICE_NAME=0
Aug 17 21:41:51 MacBook-Air InstallAssistant[590]: Env: SHLVL=1
Aug 17 21:41:51 MacBook-Air InstallAssistant[590]: Env: __OSINSTALL_ENVIRONMENT=1
Aug 17 21:41:51 MacBook-Air InstallAssistant[590]: Env: CI_DEFAULT_OPENCL_USAGE=0
Aug 17 21:41:51 MacBook-Air InstallAssistant[590]: Env: OS_INSTALL=1
Aug 17 21:41:51 MacBook-Air InstallAssistant[590]: Env: _=/System/Library/CoreServices/Language Chooser.app/Contents/MacOS/Language Chooser
Aug 17 21:41:52 MacBook-Air osinstallersetupd[591]: OSISChunkedDownload loaded...
Aug 17 21:41:52 MacBook-Air osinstallersetupd[591]: OSISAppStoreDownload loaded...
Aug 17 21:41:52 MacBook-Air osinstallersetupd[591]: Checking Software Update catalog URL https://swscan.apple.com/content/catalogs/others/index-10.12customerseed-10.12-10.11-10.10-10.9-mountainlion-lion-snowleopard-leopard.merged-1.sucatalog.gz
Aug 17 21:41:52 MacBook-Air osinstallersetupd[591]: mountDiskImageWithPath: /Volumes/Image Volume/Install macOS Sierra.app/Contents/SharedSupport/InstallESD.dmg
Aug 17 21:41:54 MacBook-Air osinstallersetupd[591]: Mounting disk image complete, results dict = {
        "system-entities" =     (
                    {
                "content-hint" = "GUID_partition_scheme";
                "dev-entry" = "/dev/disk20";
                "potentially-mountable" = 0;
                "unmapped-content-hint" = "GUID_partition_scheme";
            },
                    {
                "content-hint" = EFI;
                "dev-entry" = "/dev/disk20s1";
                "potentially-mountable" = 1;
                "unmapped-content-hint" = "C12A7328-F81F-11D2-BA4B-00A0C93EC93B";
                "volume-kind" = msdos;
            },
                    {
                "content-hint" = "Apple_HFS";
                "dev-entry" = "/dev/disk20s2";
                "mount-point" = "/Volumes/OS X Install ESD";
                "potentially-mountable" = 1;
                "unmapped-content-hint" = "48465300-0000-11AA-AA11-00306543ECAC";
                "volume-kind" = hfs;
            }
        );
    }
Aug 17 21:41:54 MacBook-Air osinstallersetupd[591]: Mount point /Volumes/OS X Install ESD
Aug 17 21:41:54 MacBook-Air osinstallersetupd[591]: osinstallersetupd registered client
Aug 17 21:41:55 MacBook-Air Unknown[508]: Aug 17 21:41:55  InstallAssistant[590] <Error>: CGColorSpaceCreateWithName failed for kCGColorSpaceITUR_709
Aug 17 21:41:55 MacBook-Air Unknown[508]: Aug 17 21:41:55  InstallAssistant[590] <Error>: CGColorSpaceCreateWithName failed for kCGColorSpaceITUR_2020
Aug 17 21:41:55 MacBook-Air Unknown[508]: Aug 17 21:41:55  InstallAssistant[590] <Error>: CGColorSpaceCreateWithName failed for kCGColorSpaceROMMRGB
Aug 17 21:41:55 MacBook-Air Unknown[508]: 2019-08-17 21:41:55.641 InstallAssistant[590:25524] NSColorList could not parse color list file /System/Library/Colors/System.clr
Aug 17 21:41:55 MacBook-Air Unknown[508]: 2019-08-17 21:41:55.676 InstallAssistant[590:25524] Failed to connect (continuePane) outlet from (IASetupWindowController) to (NSTextField): missing setter or instance variable
Aug 17 21:41:55 MacBook-Air InstallAssistant[590]: DM ..F-[DMManager(PrivateMethods) clientConforms:error:]: currentThread=32023=0x7d17 expectedThread=775=0x307
Aug 17 21:41:55 MacBook-Air InstallAssistant[590]: DM ..F-[DMManager(PrivateMethods) clientConforms:error:]: currentThread=32023=0x7d17 expectedThread=775=0x307
Aug 17 21:41:55 MacBook-Air InstallAssistant[590]: DM ..F-[DMManager(PrivateMethods) clientConforms:error:]: currentThread=32023=0x7d17 expectedThread=775=0x307
Aug 17 21:41:55 MacBook-Air InstallAssistant[590]: DM ..F-[DMManager(PrivateMethods) clientConforms:error:]: currentThread=32023=0x7d17 expectedThread=775=0x307
Aug 17 21:41:55 MacBook-Air InstallAssistant[590]: DM ..F-[DMManager(PrivateMethods) clientConforms:error:]: currentThread=32023=0x7d17 expectedThread=775=0x307
Aug 17 21:41:55 MacBook-Air InstallAssistant[590]: DM ..F-[DMManager(PrivateMethods) clientConforms:error:]: currentThread=32023=0x7d17 expectedThread=775=0x307
Aug 17 21:41:55 MacBook-Air InstallAssistant[590]: DM ..F-[DMManager(PrivateMethods) clientConforms:error:]: currentThread=32023=0x7d17 expectedThread=775=0x307
Aug 17 21:41:55 MacBook-Air InstallAssistant[590]: DM ..F-[DMManager(PrivateMethods) clientConforms:error:]: currentThread=32023=0x7d17 expectedThread=775=0x307
Aug 17 21:41:55 MacBook-Air InstallAssistant[590]: DM ..F-[DMManager(PrivateMethods) clientConforms:error:]: currentThread=32023=0x7d17 expectedThread=775=0x307
Aug 17 21:41:55 MacBook-Air osinstallersetupd[591]: Specifier (<PKPackageSpecifier>:
    {
        URL = "file:///Volumes/OS%20X%20Install%20ESD/Packages/BaseSystemResources.pkg";
        authLevel = 2;
        displayName = macOS;
        identifier = "com.apple.pkg.BaseSystemResources";
        options = 16;
        version = "10.12.6.1.1.1500089887";
    }) missing reference.
Aug 17 21:41:55 MacBook-Air osinstallersetupd[591]: Specifier (<PKPackageSpecifier>:
    {
        URL = "file:///Volumes/OS%20X%20Install%20ESD/Packages/Essentials.pkg";
        authLevel = 2;
        displayName = macOS;
        identifier = "com.apple.pkg.Essentials";
        options = 16;
        version = "10.12.6.1.1.1500089887";
    }) missing reference.
Aug 17 21:41:55 MacBook-Air osinstallersetupd[591]: Specifier (<PKPackageSpecifier>:
    {
        URL = "file:///Volumes/OS%20X%20Install%20ESD/Packages/OSInstall.pkg";
        authLevel = 2;
        displayName = macOS;
        identifier = "com.apple.pkg.OSInstall";
        options = 16;
        version = "10.12.6.1";
    }) missing reference.
Aug 17 21:41:55 MacBook-Air osinstallersetupd[591]: Specifier (<PKPackageSpecifier>:
    {
        URL = "file:///Volumes/OS%20X%20Install%20ESD/Packages/FirmwareUpdate.pkg";
        authLevel = 2;
        displayName = macOS;
        identifier = "com.apple.pkg.FirmwareUpdate";
        options = 16;
        version = "10.12.6.1.1.1500089887";
    }) missing reference.
Aug 17 21:41:55 MacBook-Air osinstallersetupd[591]: Specifier (<PKPackageSpecifier>:
    {
        URL = "file:///Volumes/OS%20X%20Install%20ESD/Packages/EmbeddedOSFirmware.pkg";
        authLevel = 2;
        displayName = macOS;
        identifier = "com.apple.pkg.EmbeddedOSFirmware";
        options = 16;
        version = "10.12.6.1.1.1500089887";
    }) missing reference.
Aug 17 21:41:55 MacBook-Air osinstallersetupd[591]: version = 10.12.6
Aug 17 21:41:55 MacBook-Air osinstallersetupd[591]: OSISCustomizationController: Using version 10.12 from InstallSystemSizes.plist
Aug 17 21:41:55 MacBook-Air osinstallersetupd[591]: OSISCustomizationController: System size: 10515609460 bytes
Aug 17 21:41:55 MacBook-Air osinstallersetupd[591]: Specifier (<PKPackageSpecifier>:
    {
        URL = "file:///Volumes/OS%20X%20Install%20ESD/Packages/BaseSystemResources.pkg";
        authLevel = 2;
        displayName = macOS;
        identifier = "com.apple.pkg.BaseSystemResources";
        options = 16;
        version = "10.12.6.1.1.1500089887";
    }) missing reference.
Aug 17 21:41:55 MacBook-Air osinstallersetupd[591]: Specifier (<PKPackageSpecifier>:
    {
        URL = "file:///Volumes/OS%20X%20Install%20ESD/Packages/Essentials.pkg";
        authLevel = 2;
        displayName = macOS;
        identifier = "com.apple.pkg.Essentials";
        options = 16;
        version = "10.12.6.1.1.1500089887";
    }) missing reference.
Aug 17 21:41:55 MacBook-Air osinstallersetupd[591]: Specifier (<PKPackageSpecifier>:
    {
        URL = "file:///Volumes/OS%20X%20Install%20ESD/Packages/OSInstall.pkg";
        authLevel = 2;
        displayName = macOS;
        identifier = "com.apple.pkg.OSInstall";
        options = 16;
        version = "10.12.6.1";
    }) missing reference.
Aug 17 21:41:55 MacBook-Air osinstallersetupd[591]: Specifier (<PKPackageSpecifier>:
    {
        URL = "file:///Volumes/OS%20X%20Install%20ESD/Packages/FirmwareUpdate.pkg";
        authLevel = 2;
        displayName = macOS;
        identifier = "com.apple.pkg.FirmwareUpdate";
        options = 16;
        version = "10.12.6.1.1.1500089887";
    }) missing reference.
Aug 17 21:41:55 MacBook-Air osinstallersetupd[591]: Specifier (<PKPackageSpecifier>:
    {
        URL = "file:///Volumes/OS%20X%20Install%20ESD/Packages/EmbeddedOSFirmware.pkg";
        authLevel = 2;
        displayName = macOS;
        identifier = "com.apple.pkg.EmbeddedOSFirmware";
        options = 16;
        version = "10.12.6.1.1.1500089887";
    }) missing reference.
Aug 17 21:41:58 MacBook-Air osinstallersetupd[591]: mountDiskImageWithPath: /Volumes/Image Volume/Install macOS Sierra.app/Contents/SharedSupport/InstallESD.dmg
Aug 17 21:42:00 MacBook-Air osinstallersetupd[591]: Mounting disk image complete, results dict = {
        "system-entities" =     (
                    {
                "content-hint" = "GUID_partition_scheme";
                "dev-entry" = "/dev/disk20";
                "potentially-mountable" = 0;
                "unmapped-content-hint" = "GUID_partition_scheme";
            },
                    {
                "content-hint" = EFI;
                "dev-entry" = "/dev/disk20s1";
                "potentially-mountable" = 1;
                "unmapped-content-hint" = "C12A7328-F81F-11D2-BA4B-00A0C93EC93B";
                "volume-kind" = msdos;
            },
                    {
                "content-hint" = "Apple_HFS";
                "dev-entry" = "/dev/disk20s2";
                "mount-point" = "/Volumes/OS X Install ESD";
                "potentially-mountable" = 1;
                "unmapped-content-hint" = "48465300-0000-11AA-AA11-00306543ECAC";
                "volume-kind" = hfs;
            }
        );
    }
Aug 17 21:42:00 MacBook-Air osinstallersetupd[591]: Mount point /Volumes/OS X Install ESD
Aug 17 21:42:00 MacBook-Air osinstallersetupd[591]: Got and processed license agreement message
Aug 17 21:42:15 MacBook-Air InstallAssistant[590]: Failed to check if a disk is FDE.
Aug 17 21:42:22 MacBook-Air osinstallersetupd[591]: Helper tool loaded
Aug 17 21:42:22 MacBook-Air osinstallersetupd[591]: Specifier (<PKPackageSpecifier>:
    {
        URL = "file:///Volumes/OS%20X%20Install%20ESD/Packages/BaseSystemResources.pkg";
        authLevel = 2;
        displayName = macOS;
        identifier = "com.apple.pkg.BaseSystemResources";
        options = 16;
        version = "10.12.6.1.1.1500089887";
    }) missing reference.
Aug 17 21:42:22 MacBook-Air osinstallersetupd[591]: Specifier (<PKPackageSpecifier>:
    {
        URL = "file:///Volumes/OS%20X%20Install%20ESD/Packages/Essentials.pkg";
        authLevel = 2;
        displayName = macOS;
        identifier = "com.apple.pkg.Essentials";
        options = 16;
        version = "10.12.6.1.1.1500089887";
    }) missing reference.
Aug 17 21:42:22 MacBook-Air osinstallersetupd[591]: Specifier (<PKPackageSpecifier>:
    {
        URL = "file:///Volumes/OS%20X%20Install%20ESD/Packages/OSInstall.pkg";
        authLevel = 2;
        displayName = macOS;
        identifier = "com.apple.pkg.OSInstall";
        options = 16;
        version = "10.12.6.1";
    }) missing reference.
Aug 17 21:42:22 MacBook-Air osinstallersetupd[591]: Specifier (<PKPackageSpecifier>:
    {
        URL = "file:///Volumes/OS%20X%20Install%20ESD/Packages/FirmwareUpdate.pkg";
        authLevel = 2;
        displayName = macOS;
        identifier = "com.apple.pkg.FirmwareUpdate";
        options = 16;
        version = "10.12.6.1.1.1500089887";
    }) missing reference.
Aug 17 21:42:22 MacBook-Air osinstallersetupd[591]: Specifier (<PKPackageSpecifier>:
    {
        URL = "file:///Volumes/OS%20X%20Install%20ESD/Packages/EmbeddedOSFirmware.pkg";
        authLevel = 2;
        displayName = macOS;
        identifier = "com.apple.pkg.EmbeddedOSFirmware";
        options = 16;
        version = "10.12.6.1.1.1500089887";
    }) missing reference.
Aug 17 21:42:22 MacBook-Air osinstallersetupd[591]: Using product <OSISSharedSupportProduct: 0x7fca96dadd80> at distance 10
Aug 17 21:42:24 MacBook-Air osinstallersetupd[591]: Using product <OSISInstallMediaProduct> based on media at /Volumes/OS X Install ESD at distance 5
Aug 17 21:42:24 MacBook-Air osinstallersetupd[591]: No available package ref for compatibility update. Ignoring.
Aug 17 21:42:24 MacBook-Air osinstallersetupd[591]: OSISDownloadOperation: totalEstimate=382.000000, significantDownload=1
Aug 17 21:42:24 MacBook-Air osinstallersetupd[591]: Operation queue started
Aug 17 21:42:26 MacBook-Air osishelperd[597]: Privilaged helper tool loaded.
Aug 17 21:42:26 MacBook-Air osishelperd[597]: Will not add removal tool because target is not /.
Aug 17 21:42:27 MacBook-Air osinstallersetupd[591]: Using product PKSecureNetEnabledProduct <file:///Volumes/Macintosh%20SSD/macOS%20Install%20Data/> at distance 5
Aug 17 21:42:27 MacBook-Air osinstallersetupd[591]: Using product <OSISSoftwareUpdateCatalogProduct: 0x7fca96fb3e30> at distance 25
Aug 17 21:42:27 MacBook-Air osinstallersetupd[591]: OSISDownloadOperation: totalEstimate=382.000000, significantDownload=1
Aug 17 21:42:27 MacBook-Air osinstallersetupd[591]: Retrieving 3 packages (5.015 GB)
Aug 17 21:42:27 MacBook-Air osinstallersetupd[591]: Retrieved package com.apple.pkg.CompatibilityUpdate (http://swcdn.apple.com/content/downloads/17/04/031-83163/n8thccuwnoqetn1kyn53bheb4nb7pw3wbv/OSX_10_12_IncompatibleAppList.pkg)
Aug 17 21:42:27 MacBook-Air osinstallersetupd[591]: No native mechanism to verify InstallInfo.plist
Aug 17 21:42:27 MacBook-Air osinstallersetupd[591]: Retrieved package com.apple.installer.info (file:///Volumes/Image%20Volume/Install%20macOS%20Sierra.app/Contents/SharedSupport/InstallInfo.plist)
Aug 17 21:52:20 MacBook-Air powerd[152]: Assertion TimedOut. Type:UserIsActive Name:'com.apple.iohideventsystem.queue.tickle.4294967965.11' Id:0x900008011 Process:hidd [System: PrevIdle DeclUser kDisp]
Aug 17 21:52:44 MacBook-Air powerd[152]: Display is turned off
Aug 17 21:52:44 MacBook-Air powerd[152]: Assertion Summary. Type:NoIdleSleepAssertion Name:'OSInstaller Setup' Id:0x10000801e Process:osinstallersetupd [System: PrevIdle]
Aug 17 21:52:44 MacBook-Air powerd[152]: Assertion Summary. Type:ExternalMedia Name:'com.apple.powermanagement.externalmediamounted' Id:0x800008000 Process:powerd [System: PrevIdle]
Aug 17 21:53:00 MacBook-Air powerd[152]: Display is turned on
Aug 17 21:53:00 MacBook-Air powerd[152]: Assertion Created. Type:UserIsActive Name:'com.apple.iohideventsystem.queue.tickle.4294967965.11' Id:0x900008020 Process:hidd [System: PrevIdle DeclUser kDisp]
Aug 17 22:08:12 MacBook-Air osinstallersetupd[591]: No native mechanism to verify InstallESD.dmg
Aug 17 22:08:12 MacBook-Air osinstallersetupd[591]: Retrieved package com.apple.dmg.InstallESD (file:///Volumes/Image%20Volume/Install%20macOS%20Sierra.app/Contents/SharedSupport/InstallESD.dmg)
Aug 17 22:08:14 MacBook-Air osinstallersetupd[591]: Verifying InstallOS.pkg/InstallESD.dmg
Aug 17 22:09:30 MacBook-Air osinstallersetupd[591]: Skipping preflighting firmware since we're booted into the Recovery OS
Aug 17 22:09:30 MacBook-Air osinstallersetupd[591]: Operation queue succeeded
Aug 17 22:09:30 MacBook-Air powerd[152]: Assertion Released. Type:NoIdleSleepAssertion Name:'OSInstaller Setup' Id:0x10000801e Process:osinstallersetupd [System: DeclUser kDisp]
Aug 17 22:09:30 MacBook-Air InstallAssistant[590]: Finished operation queue
Aug 17 22:09:34 MacBook-Air osishelperd[597]: Wrote prev-lang:kbd=en:15
Aug 17 22:09:34 MacBook-Air osishelperd[597]: Current phase is: Language Chooser
Aug 17 22:09:40 MacBook-Air osishelperd[597]: mountDiskImageWithPath: /Volumes/Macintosh SSD/macOS Install Data/InstallESD.dmg
Aug 17 22:10:13 MacBook-Air osishelperd[597]: Couldn't mount base system dmg! (error code 60)
Aug 17 22:10:13 MacBook-Air osishelperd[597]: IATOOL: Failed to mount outer dmg
Aug 17 22:10:13 MacBook-Air osinstallersetupd[591]: Unable to setup bless on disk.
Aug 17 22:13:04 MacBook-Air Unknown[508]: 2019-08-17 22:13 InstallAssistant[590] (FSEvents.framework) FSEventStreamStart: ERROR: FSEvents_connect() => Unknown service name (1102)

Can anyone shed some light on this? How do I proceed?

Answer 1

In my opinion the error message is misleading. Probably it's the same broken certification chain (as in this question & answer: El Capitan bootable installer on Mac Mini - “A required download is missing”) resulting in a slightly different message.

So download Sierra, open the dmg and the included pkg and install the Sierra installer.app to /Applications.

From there create a new installer thumb drive with:

sudo /Applications/Install\ macOS\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ macOS\ Sierra.app

Replace MyVolume with the name of your freshly erased thumb drive volume (probably "Untitled").

Boot to the thumb drive and install Sierra.

Answer 2

This sucks when it happens I know. I've had this happen when creating a USB installer from a Mac OS DMG that was downloaded with Safari. Before we start you need to MAKE SURE you are creating an installer USB from a Mac OS Sierra installer that is around 5.2GB. If you are trying to do it from one downloaded from the App store that is smaller than that then you are downloading an incomplete installer meant to be used only for upgrading within the Operating system (i.e. clicking on it in the Applications folder to install)

Here is a link on how to download the actual "Full" installer:

https://mycyberuniverse.com/macos/how-download-complete-macos-high-sierra-installer-app.html

So to continue. For some reason safari treats certain files differently especially iPhone firmware but also in some cases Mac OS dmg's. Don't ask me why because I can't remember the info since it was so long ago when I read it. Download the DMG with Firefox or Chrome and then Recreate the Installer USB. Stuff happens and DMG's get corrupted so my "go to" when creating a USB installer and things go wrong is to redownload the DMG and don't use Safari. Once you've rooted out that the DMG is good then you can move on to all the other helpful suggestions. Good luck! Oh and once you get that installer working HIDE IT FOR NEXT TIME SO THAT YOU DON'T ERASE IT HA HA!

If you have a working Mac and you aren't Terminal Savvy then just use DiskMaker X to create the bootable USB installer.

Answer 3

When reinstalling macOS Sierra from internet recovery we get the following error:

osishelperd[547]: mountDiskImageWithPath: /Volumes/Untitled/macOS Install Data/InstallESD.dmg
osishelperd[547]: Couldn't mount base system dmg! (error code 110)
osishelperd[547]: IATOOL: Failed to mount outer dmg

The issue with Sierra as with most of the old installers re-downloaded from the App Store (apparently from the recovery too) is that the downloaded InstallESD.dmg is not in a UDZO format, but a XAR archive or rather a XAR wrapper and within it is the real InstallESD.dmg in UDZO format. the XAR wrapper needs to be removed to access the inner package. You can use pkgutil or XAR command. The XAR tool is a product of the defunct OpenDarwin project. It is a command-line tool, like pkgutil. But while pkgutil works on flat packages and the new receipts database, XAR works exclusively on flat packages.More info about different Apple archives you can find here and here. The commands for the conversion are:

pkgutil --expand /Volumes/Untitled/macOS\ Install\ Data/InstallESD.dmg  /Volumes/Untitled/Sierra && mv /Volumes/Untitled/Sierra/InstallOS.pkg/InstallESD.dmg /Volumes/Untitled/macOS\ Install\ Data/InstallESD.dmg && rm -r /Volumes/Untitled/Sierra

From this point one can create a USB installer from the InstallESD.dmg or Install Sierra onto a disk. To install Sierra execute the following providing the drive where the macOS Install Data folder is downloaded to a drive labeled 'Untitled':

cd /Volumes/Untitled/macOS\ Install\ Data/
/usr/bin/hdiutil attach InstallESD.dmg -nobrowse
cd /Volumes/OS\ X\ Install\ ESD/Packages/
installer -pkg OSInstall.mpkg -target /Volumes/Sierra/ -verboseR

To create a USB Install disk follow this:

• Attach InstallESD.dmg (if not already attached):

/usr/bin/hdiutil attach /Volumes/Untitled/macOS\ Install\ Data/InstallESD.dmg -nobrowse

• Attach BaseSystem.dmg

/usr/bin/hdiutil attach /Volumes/OS\ X\ Install\ ESD/BaseSystem.dmg -nobrowse

• Get the disk name of the BaseSystem.dmg:

diskutil list virtual | grep "OS X Base System"
  1:                  Apple_HFS OS X Base System        2.0 GB     disk9s1

• Find the USB number with diskutil list
• Format the USB:

diskutil partitionDisk disk7 HFS+ USBSTICK 100%

• Get the details of the USBSTICK:

diskutil list
/dev/disk7 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:      GUID_partition_scheme                        *15.7 GB    disk7
   1:                        EFI EFI                     209.7 MB   disk7s1
   2:                  Apple_HFS USBSTICK                15.4 GB    disk7s2

• Restore "OS X Base System" onto Apple_HFS USBSTICK

asr restore --source /dev/disk9s1 --target /dev/rdisk7s2 --erase --noprompt --noverify

• Remove the symlink for Packages folder:

rm -r /Volumes/OS\ X\ Base\ System/System/Installation/Packages

• Copy the Packages folder to "OS X Base System" Volume inside /System/Installation/ subfolder:

cp -rpv /Volumes/OS\ X\ Install\ ESD/Packages /Volumes/OS\ X\ Base\ System/System/Installation/Packages

• Copy BaseSystem.chunklist and BaseSystem.dmg to the root of the USB installer:

cp /Volumes/OS\ X\ Install\ ESD/BaseSystem.chunklist "/Volumes/OS X Base System"
cp /Volumes/OS\ X\ Install\ ESD/BaseSystem.dmg "/Volumes/OS X Base System"

• Detach the mounted images:

/usr/bin/hdiutil detach /Volumes/OS\ X\ Install\ ESD
/usr/bin/hdiutil detach /Volumes/OS\ X\ Base\ System