How to decrease size of macbook pro (early 2011) boot partition? My macbook pro early 2011 has an SSD with 2 partitions (disk0s1 = 50Gb for time machine backups and disk0s2 =206Gb boot and data). 
I have somehow managed to totally fill up my boot partition to over 205GB and the macbook does not boot. Using the diskutility I cannot decrease the 50GB disk0s1 partition and increase the disk0s2 partition. The repair tool ends with an error also.

What can I do to either copy the data from the partition or decrease the partition so that the mac can boot again?
I think it's impossible (pre-APFS) to delete the first partition. You can expand a partition 'upwards' into free space, but you can't move down a later partition.

If you think that stuff on the boot volume could be deleted until there's sufficient free space, then that might be enough to get you up and running for the time being.
Easiest would be to boot from an external drive and then explore the internal volume from there. (Or using Target Mode from another Mac.) Alternatively, you could mount the boot volume in Recovery's Terminal and delete files from there, if you're comfortable with that.

But most solutions will require you to copy everything off, wipe the disk and then put it all back. A utility like Carbon Copy Cloner or SuperDuper! can make disk images easily.



IMPORTANT WARNING

Before attempting any adjustment to the disk partition, you need to make a backup of the boot volume on a separate device, in case it goes wrong and you wipe the disk.

There is absolutely no value in having a backup partition on the same device as the source data. If the SSD fails or you wipe it; if the laptop gets stolen or catches fire: you've got nothing. 

Backups need to be on a separate physical device.