, LinuxThreads may still be seen on production systems, particularly those using version 2.4 or lower of the Linux kernel, as NPTL requires facilities which were specifically added into the 2.6 version of the kernel for its use.
LinuxThreads can be found on production systems, especially those using older Linux kernel versions like 2.4 or lower, primarily because NPTL needs capabilities that were added in the 2.6 kernel version.