Fixing the El Capitan Keychain error 100001

Here is a fix for a pernicious error that prevents users from accessing a Debian server that offers TimeMachine disk space.

The very helpful ( /s) error message:

Keychain error 100001 occurred while creating a System Keychain entry
for the username “user name” and URL “afp://user
name@my_Airport._afpovertcp._tcp.local./backup”.  |

At this point, check - in the terminal - if your access to the keychain is restricted:

ls -l @Oaen /L*/Keyc*

If so, this might help:

Fix

• Boot the Mac into ‘Recovery Mode’.

  Shutdown, and restart-while-holding the ‘command’ and ‘r’ keys. So, not command R, just r. You hold until the Apple logo appears. If this is the first time you boot into Recovery Mode, you’ll have to accept some licence terms. TLDR;

• open terminal, which you can find in the Utilities menu.

The bash shell in Recovery Mode uses the USen keyboard layout.

enter:

chflags norestricted /V*/*/L*/Keyc*/*

and reboot.

• login as you would usually, and again, open terminal

enter:

sudo -s
xattr -c /L*/Keyc*/*

After this, you can use your TimeMachine.

Update thanks to Linc Davis, detailing this on Apple’s discussion forum.