How to delete files in recovery mode? My HD is 100% full and the macbook only starts in recovery mode.

OK - here's the promised follow up. I'm guessing if you didn't have a backup, you'd like to be able to keep your files.

Just to narrow things down, which model MacBook? I know some people post questions here on the older models even though this forum is theoretically for the 2015 and later SSD-based MacBook.

There are a couple of things that might work.

1) You'll need another Mac that can connect to yours in target disk mode. From there you can treat it like an external drive and copy over enough files before deleting them. If you can get a Genius Bar appointment at a local Apple Store they might be able to do this for you.

https://support.apple.com/en-us/HT201462

2) You'll need an external drive big enough to install the entire OS. This can be a hard drive even if you've got an internal SSD. You could use Recovery HD, Internet Recovery, or an OS install disc (if you're talking about an older version MacBook) to run Disk Utility to format the external drive, and then install the OS on the external drive volume. You would then boot from the external drive by holding down option at power up and selecting the external drive. Your internal drive would then be visible as another volume where you could use Finder to copy over files and then delete them. Maybe copy over to something like a USB flash drive if you really need to be able to use those files once your internal drive can boot again.

The biggest caveat is that if you've got an SSD that's been reconfigured (it will do it automatically) for the APFS file system, you're going to need High Sierra to access your internal drive. Internet Recovery and Recovery HD will only install the original OS that came with your MacBook. So if it installs Sierra, you'll need to update to High Sierra on the external before you can access High Sierra without some esoteric command line stuff.

There are more specific recommendations for buying the equipment to do this depending on what machine you have.

That is not possible. You will have to erase the drive and install macOS from scratch. There are no other options at this point, I'm sorry to say.

Install El Capitan or Later from Scratch

1. Restart the computer. Immediately after the chime hold down the CommandandRkeys until the Apple logo appears. When the Utility Menu appears:
2. Select Disk Utility from the Utility Menu and click on Continue button.
3. When Disk Utility loads select the volume (indented entry, usually Macintosh HD) from the Device list.
4. Click on the Erase icon in Disk Utility's main window. A panel will drop down.
5. Set the Format type to Mac OS Extended (Journaled.)
6. Click on the Apply button, then wait for the Done button to activate and click on it.
7. Quit Disk Utility and return to the Utility Menu.
8. Select Install OS X and click on the Continue button.

This will install the version of OS X you had installed.

Kappy wrote:

When a drive is 100% filled there is no way to remove files because the directory is now corrupted to the point where it is no longer usable without being reformatted.

I think it's still worth a try to see if the drive isn't corrupted. Even if it is corrupted it might be possible to recover data from it before reformatting, although it might take an expensive professional with professional tools. It's hard to put a price on how valuable data is to any particular user. I've certainly heard of people who only stored their irreplaceable photos on a single computer drive, and were willing to pay a small fortune to recover as much data as possible.

The worst (save time wasted) that could happen with my second suggestion is that it doesn't work, the OP just resets with a clean OS install, and now there's an external drive that can be used for Time Machine/CCC/SD backups once the internal drive is back and working.

When a drive is 100% filled there is no way to remove files because the directory is now corrupted to the point where it is no longer usable without being reformatted.

Juha358 wrote:

How to delete files in recovery mode? My HD is 100% full and the macbook only starts in recovery mode.

I wouldn't erase right away. I think there are ways to copy over and remove files such that there's enough space on your drive to be able to boot. I'll follow up.