and tries to create schema directories right in /tmp. Perhaps specifying a different (and empty) tmpdir explicitly in my.cnf is a workaround.
Responsibility to create a dedicated empty directory inside tmpdir may belong with either innobackupex or SST script. Fixing SST is probably the right thing as it is responsible for the rest of the setup.
So it looks like innobackupex is run with /tmp as an argument (default tmpdir?):
perl /usr/bin/ innobackupex --defaults- file=/run/ shm/galera0/ mysql/etc/ my.cnf --user=root --password=rootpass --socket= /dev/shm/ galera0/ mysql/var/ /mysqld. sock --galera-info --stream=tar /tmp
and tries to create schema directories right in /tmp. Perhaps specifying a different (and empty) tmpdir explicitly in my.cnf is a workaround.
Responsibility to create a dedicated empty directory inside tmpdir may belong with either innobackupex or SST script. Fixing SST is probably the right thing as it is responsible for the rest of the setup.