If you ever encounter a Linux dir in which you cannot write even when you're sure you have write permissions on it, check the ACLs. You may find someone doesn't particularly like you. 😞
Learned by kevin-perez on Mar 11, 2022
-> getfacl /tmp # file: tmp # owner: root # group: root # flags: --t user::rwx group::rwx other::rwx user:my_user:--- # this means "screw u and only u"