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As far as installing or upgrading OSes goes, Apple’s installer app is straight-forward and simple to use. Just launch the app, click through a few windows in the wizard, and the scripts built into the installer take over and perform the rest of the work. When performing a clean install, you only need to boot the installer first, then the rest of the steps apply like clockwork.
Only, what happens when it encounters an error and refuses to continue the install or upgrade process? More to the point, what can resolve the dreaded “corrupt installer” message, which commonly occurs during the pre-install phase and halts the task altogether with this ambiguous error code?
The good news is that barring any major issue with your system’s hardware, the corrupt installer message does not have to spell certain doom for your installation task. As a matter of fact, most of the time the issue causing the error in the first place has nothing to do with data corruption.
SEE: Software quality control policy (Tech Pro Research)
Below we’ll discuss three solutions that could be used to rid yourself of this error once and for all.
1. Verify the integrity of the file
While it is unlikely that the installer app is corrupt, it’s not out of the realm of possibility that it could be a bad download. Before proceeding, run the command below in Terminal against your installer to determine its hash, or checksum value.
shasum /Applications/macOS Mojave Installer.app
The hash value refers to the integrity of the file, or put another way, determines if the file has been modified in any way by calculating the value based on the hashing algorithm and comparing them to those posted by the developer. If the values match, the file is deemed unmodified or intact. However, if the values do not match, then there is a reason to believe that the data could have been modified, either maliciously or unintentionally, likely due to an incomplete download.
2. Set the correct time/date
With the file’s integrity verified, next look at the time/date and make sure it is set correctly on the device. While this typically isn’t an issue when performing an in-place upgrade from the GUI, it can occur frequently when performing a clean install as the time being off could cause the install to fail without further warning.
By selecting Utilities | Terminal from the toolbar in the Recovery Partition, you can enter the command below to set the current date/time. After the command is executed, quit Terminal and retry the macOS installation.
3. Connect to the internet
The file’s integrity is verified and the time/date is set properly, but you’re still getting the corrupt data error. The final item to check is the internet connection. Believe it or not, the installer app has been known to phone home to Apple’s servers to verify that it can be installed on the device. If there’s no internet connection, the process will fail, as will the task itself.
However, by connecting the device to a wired connection (or configuring the wireless connection)—directly from the Recovery Partition —the app will be able to complete its call back to Apple’s servers and be given the green light to continue the installation unhindered.