Where do I get the latest libc?

There are two primary versions of libc.so in use today. (If you have an older installation, you may have an even older version of libc, but that's obvious, right?)

The one used in most of the current distributions is libc-2.x.x.so, also informally known as libc6; this is the GNU libc, which is multithread-safe, among other things. It can be downloaded from the Free Software Foundation's main FTP repository.

The other libc, primarily used by sites running older versions of Linux for various reasons, is libc5. The canonical place to get the latest libc5 is on Metalab, formally known as "Sunsite", although many other repositories exist.

Note that there are issues with upgrading from libc5 (the older C library) and libc6 (also known as "glibc".) Don't upgrade from libc5 to libc6 without full awareness of what the issues are; check the documentation for your distribution. In general, it is a lot safer and a lot faster to upgrade your distribution of linux. But, if given that warning you are still determined to upgrade your system manually, read this howto very carefully.

In particular, do not attempt to upgrade slackware systems. If you did not know content of this page, then you probably do not know enough to upgrade a slackware system. This is why slackware is generally considered to have relatively major disadvantages when compared to other distributions of linux.