So a few weeks ago, I was playing around with building LLVM/Clang from source on my Azure hosted Ubuntu VM (a story for another time). The process would take a few hours, so I’d start it running in the evening, log out. But when I came back to check up on it in the morning, I kept getting these errors:

Linking CXX executable ../../../../bin/clang
collect2: error: ld terminated with signal 9 [Killed]
make[2]: *** [bin/clang-3.5] Error 1
make[1]: *** [tools/clang/tools/driver/CMakeFiles/clang.dir/all] Error 2
make: *** [all] Error 2

Obviously, something bad was happening, so I Googled around and it seems that the error often occurs when linking and not having enough memory. But wait, I’m sure I have plenty of memory in my Azure VM, 3.5 GB of RAM and some extra Swap space to boot.

$ free -h
             total       used       free     shared    buffers     cached
Mem:          3.4G       871M       2.5G       416K        78M       600M
-/+ buffers/cache:       192M       3.2G
Swap:           0B         0B         0B

OH…

.. and then I found this blog post.

Really, Microsoft? No Swap space? Not even a little?

Let’s go ahead and use the good ‘ol estimate of ~2x my physical RAM for the Swap space.

$ sudo fallocate -l 7g /mnt/swap7gb
$ sudo chmod 600 /mnt/swap7gb
$ sudo mkswap /mnt/swap7gb
$ sudo swapon /mnt/swap7gb

And now I have Swap space!

$ free -h
             total       used       free     shared    buffers     cached
Mem:          3.4G       871M       2.5G       416K        78M       600M
-/+ buffers/cache:       192M       3.2G
Swap:         7.0G         0B       7.0G

That’s much better.

EDIT: … or I guess I could have just snuck into Microsoft’s server farm and connected a light timer to the rack that was hosting my VM.