Making install media with El Capitan (with access only to Recovery) Manually installing.pkg files. Making install media out of partial macOS installers (“not a valid OS installer application”) a. From the El Capitan download. Installer from Recovery/App Store (any macOS version) El Capitan installer can’t be verified.
Start up from macOS Recovery
Determine whether you're using a Mac with Apple silicon, then follow the appropriate steps:
Apple silicon
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. Mac OS X El Capitan – Performing Hard Reset (Factory Settings) Step 01. Shut Down your Mac. Press and Hold the Command + R keys at the same time and Turn your Macbook on while holding down the Command + R keys. Release all keys when the Apple logo appears on the screen. Close the Terminal window and click to Reinstall macOS. If you still have the error message then reset PRMA/NVRAM: Power off your Mac. Press your Mac's power button and then hold these four keys at the same time: ⌘ + option + P + R. Continue holding the keys until your Mac.
Turn on your Mac and continue to press and hold the power button until you see the startup options window. Click the gear icon labeled Options, then click Continue.
Intel processor
Make sure that your Mac has a connection to the internet. Then turn on your Mac and immediately press and hold Command (⌘)-R until you see an Apple logo or other image.
If you're asked to select a user you know the password for, select the user, click Next, then enter their administrator password.
Reinstall macOS
Select Reinstall macOS from the utilities window in macOS Recovery, then click Continue and follow the onscreen instructions.
Follow these guidelines during installation:
- If the installer asks to unlock your disk, enter the password you use to log in to your Mac.
- If the installer doesn't see your disk, or it says that it can't install on your computer or volume, you might need to erase your disk first.
- If the installer offers you the choice between installing on Macintosh HD or Macintosh HD - Data, choose Macintosh HD.
- Allow installation to complete without putting your Mac to sleep or closing its lid. Your Mac might restart and show a progress bar several times, and the screen might be empty for minutes at a time.
After installation is complete, your Mac might restart to a setup assistant. If you're selling, trading in, or giving away your Mac, press Command-Q to quit the assistant without completing setup. Then click Shut Down. When the new owner starts up the Mac, they can use their own information to complete setup.
Other macOS installation options
When you install macOS from Recovery, you get the current version of the most recently installed macOS, with some exceptions:
- On an Intel-based Mac: If you use Shift-Option-Command-R during startup, you're offered the macOS that came with your Mac, or the closest version still available. If you use Option-Command-R during startup, in most cases you're offered the latest macOS that is compatible with your Mac. Otherwise you're offered the macOS that came with your Mac, or the closest version still available.
- If the Mac logic board was just replaced, you may be offered only the latest macOS that is compatible with your Mac. If you just erased your entire startup disk, you may be offered only the macOS that came with your Mac, or the closest version still available.
You can also use these methods to install macOS, if the macOS is compatible with your Mac:
- Use the App Store to download and install the latest macOS.
- Use the App Store or a web browser to download and install an earlier macOS.
- Use a USB flash drive or other secondary volume to create a bootable installer.
Recently, I reinstalled macOS on my device. Throughout the process, manyattempts failed miserably. But I now have some experience and assorted hints onwhat to try.
DISCLAIMER: All information in this post is provided as-is, and some of it mayvoid your warranty. Neither Chris Warrick nor Apple will be responsible for anydamage to your devices caused as a result of using information in this post.
Contents
The best, safest, least error-prone way to do an install is with a USB stick.Unfortunately, making a USB stick with the macOS installer on it is a nuisance.The expected way to produce macOS install media is to download the installerfrom App Store/Software Update, and run the createinstallmedia command-lineprogram included with that installer app. All is well, as long as macOS works.If it doesn’t, and Recovery can’t install it for you, that can be difficult tosolve.
Apple does not make macOS images publicly available. That’s probably to makeHackintoshing this little bit harder, but this also affects legitimate users.The only thing you can download from Apple is El Capitan. Apple offersInstallMacOSX.dmg on theirwebsite. If you take a look at the instructions, you will see that this isnot a bootable OS X image. This image has a .pkg package. This package isexpected to install /Applications/Install OS X El Capitan.app. Well, we’rein recovery, we can’t install stuff. So, let’s do this the manual way.
Turns out the .pkg format is just an archives all the way down, with allarchives being different formats (at least three).
The first archive is the .pkg file itself. Those files are in XAR format, which was invented by theOpenDarwin community. You can either extract it with pkgutil --expandfoo.pkg foo_files (the last argument is the destination directory, can beanything, will be created by pkgutil) if you have access to that command (it’savailable in Recovery OS), or you can try the xar utility as xar -xffoo.pkg. The structure produced by both tools is a bit different, but we canwork with both.
The second archive-in-archive is the Payload. It’s a gzipped cpio archivethat contains the files installed by this package. If you have BSD tar(default on macOS, easily installable on Linux), you can just do tar -xvf Payload.Otherwise, you can use gunzip -c Payload | cpio -i (or gzcat). Thatwill extract all the files the package has.
Another nested archive is the Scripts archive, although note thatpkgutil will extract it automatically. If it’s not extracted, it’s actually.cpio.gz again, with the same way to extract it.
(PS. If you have 7z around (on Windows/Linux as well), you can just pointit at all the compressed files mentioned in this paragraph.)
Let’s expand the El Capitan package.
We’ve got the installer app, which is what we need to create an install image.Great, let’s try it!
Oh, we’ve got a problem. Turns out there’s one more thing we need to take careof, and it’s the scripts. MacOS packages have scripts, typically shell scripts,that are run at various stages in the install process. We can look at thePackageInfo file, or just look in the Scripts folder, to see thatthere’s an link_package script we need to run. This script creates aContents/SharedSupport directory inside the installer app, andcopies/hardlinks the InstallESD.dmg file (which is the install formerly-DVDimage) to that directory. Let’s try doing this on our own:
And it works! createinstallmedia will now produce valid install media.
If you are in Recovery, you can find an Install app on the filesystem. If youtry to run it, you will get the same error as in the previous paragraph:
This also happens with some older macOS versions, where you get a small.app from the App Store, and that app does the actual download.
Whatever the issue was, we need to download the install files with theinstaller. Open the installer and let it run until the download finishes. Ifthe app asks you to reboot, quit it at this point. If it never asks, you canstill find a way to get files out (after a failed install, they should not beremoved).
The install files can be found in /macOS Install Data on the destinationvolume. For older versions, you will just have InstallESD.dmg, newerversions add more and more files, some of which are hardware-specific (andCatalina has InstallESDDmg.pkg, because Apple loves nesting archives for noreason!). However many files you find, you can just:
Copy
Install macOS Catalina.appto a read-write volume.Copy the contents of
/Volumes/TARGET/macOS Install DatatoInstallmacOS Catalina.app/Content/SharedSupport. Make sure you account for hiddenfiles, if any (copy the entire directory). If you did this correctly,InstallESDDmg.pkg(orInstallESD.dmgon older verisons) is in theSharedSupportdirectory (not in a subdirectory).Run
createinstallmedia. It should now consider the installer valid. Theavailable options differ slightly depending on the OS version.
If you get this error, it might be because Apple’s signing keys expired, orbecause of other date/time weirdness. Regardless, you can force an install ifyou are sure the installer is not damaged with this command (source):
While messing with all the installer stuff, I found out a fewinteresting/worrying things about the download process.
The first one is that the macOS installer uses plain HTTP without encryption todownload files. That opens you to all the standard issues — an attacker canreplace files you download, and the protocol doesn’t do anything to detecterrors (the installer will verify files, but where do the checksums comefrom?).
The second one is how the download happens. You might have noticed it to be abit slower than usual traffic. The download happens in 10 MB chunks, using theRange HTTP header. The installer asks for 10 MB, gets it, saves, asks foranother chunk. Repeat that over 800 times, and the overhead of the entire HTTPdance becomes noticeable. (I haven’t checked, but I hope the installer at leastuses Keep-Alive. I wouldn’t be particularly surprised if it didn’t, though.)
But this raises another question. The servers clearly support partial downloads.And yet, if your network disconnects during the download, your downloadprogress for that file is reset, and in Catalina, you can go from 8 GB back to500 MB if you’re particularly unlucky. The question is, why? Thisinfrastructure should make it trivial to continue the download, perhapsdiscarding the most recent chunk if you’re concerned about that download of itbeing unsuccessful.
The first time you boot a Mac after a clean install, it starts the SetupAssistant. This app asks for basic OS settings (locale, date/time, useraccounts), and also lets you restore user data from backups.
Sometimes, you might want to access the Terminal or Console from that screen.You can do that with Ctrl + Opt + Cmd + T and Ctrl + Opt + Cmd + C respectively (source).
How could that come in handy? For example, if you want to check if the backupdrive still worked and if the process isn’t stuck (I wrote a test file and alsochecked top).
A few months later, in December, I upgraded to Big Sur and then installed Windows 10alongside it in Boot Camp. I then did some more hacks, which led totwo unbootable OSes.
As part of the upgrade, I had prepared install media and used it to install (soit wouldn’t fail, as it did last time), and made a .dmg of it with DiskUtility. (Also, Apple won’t tell you this, but you need to give Disk UtilityFull Disk Access for disk imaging to work. Otherwise, you get a crypticerror.) I erased the USB drive after installing, but hey, I could get it back.I booted into Internet Recovery and restored my image. Big Sur failed to bootand showed a 🚫 sign. I triedrestoring my Catalina image from the previous reinstall, and that didn’t workdue to a size mismatch. I used a different USB drive than these months ago (Ididn’t have that one with me at the moment), and apparently the one I used hada different size (both are marketed as 16 GB). The images could be mountedfine, and createinstallmedia should have worked, likely producing abootable drive.
Time Machine is Apple’s magical backup solution. Time Machine saves snapshotsof your entire disk. It’s supposed to help restore files that were deleted orchanged in an unwanted way, or help you restore a full macOS install.
Time Machine is great at file recovery, but none of my 3 system restoreattempts were successful. Attempt #1 was a full Time Machine System Restore,from Recovery, back in June. It failed partway through, it couldn’t readeverything from the disk. There might have been underlying hardware issues withthat failure, so I had another attempt.
Attempt #2 was a Migration Assistant restore, as part of the initial setup.This one succeeded, and things worked… except for one fairly important app.This app requires online activation with the vendor, and it wouldn’t reactivateafter the install. Whatever the third-party vendor is doing didn’t like thereinstall. I tried to nuke all the things in ~/Library related to theirsoftware, and ran their nuke-everything uninstaller, but that didn’t work.I reinstalled from scratch and copied over my files, settings and apps from theTime Machine drive.
Attempt #3 involved the System Restore again, this time for the Decemberreinstall. The hardware issues were all fixed in the meantime, so I went for aTime Machine System Restore.
Issue #1: Internet Recovery booted into Catalina. There was an issue on Apple’sside, Big Sur was unavailable in Internet Recovery in December. TMRecovery will not restore a backup created with a newer version of macOS thanyou’re booted into, so I was forced to restore a slightly older Catalinabackup. (I spent most of my time in Windows during that weekend, so other thanthe need to upgrade macOS to Big Sur again, I didn’t really lose any data dueto this.)
Issue #2: It wasted time computing an inaccurate size estimate. Beforerestoring a backup, macOS first checks if it will fit on your drive. When itdoes that, an indeterminate progress bar is shown. macOS won’t tell you theresult of that computation, but you can read the final value from the fullInstaller Log (Cmd + L). On my Mac, the value was 96.2 GB. I was at the Macwhen it was getting close to that value. 94, 95, 96, 96.1, 96.2, 96.3… hold ona second, 96.3 GB? Hopefully that’s just a bunch of extra things that areinstalled from the system image directly, or something like that, right? Ofcourse, since the progress bar is based on the pre-computed size, it becameindeterminate and I couldn’t tell when it would end. 98, 100, 110, 120, 121.2GB is where it ultimately ended. So, not only did it waste 20+ minutescomputing a size, it was off by 25 GB.
Issue #3: The restore didn’t work. The System Restore finished and claimed tohave succeeded, but macOS wouldn’t boot. It showed an Unrecoverable error,SecurityAgent was unable to create requested mechanism. Most people who had asimilar error had it caused by a botched TeamViewer uninstall; I didn’t havethat installed, and it was referring to a different component. So, wipe andfresh reinstall it is.
I copied my stuff from the TM drive, and it was acting weird. Some apps failedto load their settings copied into Library, others started with a “Move to/Applications?” prompt (even though they were in that directory). For somereason, those files had some hidden attribute set on it. I worked around it byputting files in a .zip archive with Keka, and then unzipping them;xattr might also help. (The attribute was likely com.apple.quarantine.)
After I got the Mac to work, I reinstalled Windows and set up rEFInd, and itnow works fine. (I only use rEFInd because I want virtualization in Windows,and that doesn’t work unless you’re warm-rebooting from macOS. I don’t needanything more advanced than the Option key boot menu, but Apple made me use athird-party bootloader.)
We now go back to the original post from June.
Dear Progress Bar Designers: can you please make your progress barsfunctional? The macOS progress bar might look sleek at just 7 px (non-Retina)/6pt = 12 px (Retina) high, but at the same time, you’re looking at individualpixels if you need to know if it works or if it’s stuck. I have had to point mymouse cursor at the end of the filled-in part just to know if it’s working ornot. Or sometimes, put a piece of paper in front of my screen, because there isno mouse cursor when macOS installs on the black screen. How to makethat progress bar easier to use and more informative? Just add numbers on top ofit. For long-running processes, I wouldn’t mind progress bars that said“12.34%”. That specific Setup/Migration Assistant window should be changed (itonly has a remaining time estimate and transfer speed, it should also showmoved data/total size), but wouldn’t more things benefit from a clearindication of the progress? Yes, perhaps it looks less sleek, perhaps itrequires more space for the bar.
Just compare: which is easier to parse? Which is more informative?
Reinstall Mac Os El Capitan
Installing Mac Os El Capitan
I’d honestly be happy enough with option 2, at least it can be read easily andyou can remember the number instead of a vague position.
Reinstall Mac Os El Capitan Error
After all this, I managed to get macOS Catalina installed. After variousfailures in built-in El Capitan recovery and Catalina Internet Recovery, I firstinstalled El Capitan with this hack, then jumped to Mojave because I thoughtthe new Software Update would help (it didn’t, same installer, samefailed-to-extract-package issue), then made a Catalina USB stick, and itfinally clean-installed, but I was worried about the backup disk’s operation,and I used a proxy on my local network to try and speed up Catalina downloadswithout much improvement… but hey, at least it works. Apple should really makeit easier to install their OS and to make boot media even when stuff doesn’twork, even from Windows. The Hackintosh folks can just find someone with aworking Mac and ask them to download from App Store and make install media, orfind less legitimate sources, they probably don’t care as much. But if my ownsystem crashes, I’d probably want to get working install media immediately,myself, and from Apple. Without all this mess.