tlmgr is the name of the package and configuration manager included in TeX Live. It operates completely separately from any package manager the operating system may provide. The full documentation for tlmgr is available (updated nightly), or you can run tlmgr --help.
If you installed MacTeX, precede the commands below with sudo, since MacTeX installs as root.
Occasionally new versions of tlmgr are released. Your installed tlmgr will notice and ask you to update it before updating anything else. The command to do this is:
tlmgr update --self
After any updates of tlmgr, you can then run, for instance, tlmgr update --all, which will update (including additions and removals) all other packages in your installation that have been changed on the server. Authors frequently release new versions of their work to CTAN, which is propagated into TeX Live.
We maintain a separate history of tlmgr changes.
You may end up in a situation where tlmgr itself does not run due to Perl errors, failed updates, tlpdb changes (Unknown directive...), or some other reason. If this happens, the simplest way forward is to download and run update-tlmgr-latest.sh (Unix) or update-tlmgr-latest.exe (Windows). These are self-extracting archives which include all the infrastructure files. Running them should restore tlmgr to a coherent state.
Before running them, be sure your PATH is set to use the current TeX Live bin directory; the recovery archives use kpsewhich from PATH to figure out where to unpack themselves.
You can get the bleeding-edge tlmgr (e.g., because testing was requested and you'd like to try it), from a separate repository named ‘tlcritical’. This directory is updated nightly from the development sources.
The TeX Live Utility on MacOSX provides a convenient way to try this. You can also try tlcritical on any platform using tlmgr: the following command will show you what will be updated, along with commentary that updates to tlmgr itself are present (ignore the urls in that commentary).
tlmgr --repository=ftp://tug.org/texlive/tlcritical update --list
To actually do the update, use --self instead of --list; don't forget to keep the explicit --repository option, as given.
If you have trouble connecting to tug.org via ftp, you can also get tlcritical via rsync. First copy it into its own separate directory on your machine, and then tell tlmgr to use that directory:
rsync rsync://tug.org/tlcritical/ /new/local/dir tlmgr --repository=/new/local/dir update --list
You can switch back to the standard repository by downloading and running update-tlmgr-latest, as described in disaster recovery section just above.
Another welcome form of testing is trying the pretest which is available for a time before each official release.
Please email bug reports or other comments to the tex-live mailing list.