After switched to use Linux, I use vim-latex to extand vim for LaTeX editing. However, sometimes I would encounter errors like package not found. I thought that is because vim-latex supports limited packages (under ~/.vim/ftplugin/latex-suite/packages/), but actually vim-latex is just the plugin to turn vim into a LaTeX editor, while the complier behind it is something else, for example TeX Live.
TeX Live has its own package manager called tlmgr. This post documents some issues I had to install absent package for TeX Live.

Issue 1

When I first tried to execute tlmgr to install a package, it terminated with

(running on Debian, switching to user mode!)
cannot setup TLPDB in /home/bambo/texmf at /usr/bin/tlmgr line 5308

It turns out that I have never use tlmgr with my user account before, so I have to initialize it with the following command:

tlmgr init-usertree

Issue 2

After fixed issue 1, I am able to run tlmgr to download the package, but it dismatched at checksum. So it reported

Unknown directive ...

That is because the package repository version dismatch. By default my package repository is the latest, while I need to use the 2015 archive for compatibility. To show and configure the repository, use commands:

tlmgr repository
tlmgr option repository ftp://tug.org/historic/systems/texlive/2015/tlnet-final

After that, I am able to install new packages, ulem.sty for instance:

tlmgr install ulem

Credits

• tlmgr cannot setup TLPDB - Thank ppr, your answer helps me make the first step.
• How do I install an individual package on a Linux system? - Thank to the discussion in this thread, because I do not like to install a lot of packages unconsciously.
• How to install a package from an older version of TeXLive? - Thank mpg and Fab for your answers.