nc-indicators is a tray applet for X11 based GNU/Linux systems that shows the current CPU and memory consumption of the system. Since it's a tray applet you can use it with any panel (e.g. gnome-panel, i3bar, lxpanel) and you don't have to depend on the panel's own solution.
As it's a graphical GTK app and the implementation language is
Haskell, we use the ghc-musl Docker image to create an executable which
though dynamically linked, has the dependent .so files under the
same directory as the executable, and thus the whole package can be
distrubuted as a tar.gz.
brooks:/tmp $ docker run -v /tmp/x:/tmp/x -it --rm nilcons/ghc-musl
/ # cd /tmp
/tmp # git clone https://github.com/nilcons/nc-indicators
Cloning into 'nc-indicators'...
remote: Counting objects: 52, done.
remote: Total 52 (delta 0), reused 0 (delta 0), pack-reused 52
Unpacking objects: 100% (52/52), done.
Checking connectivity... done.
/tmp # cd nc-indicators/
/tmp/nc-indicators # cabal install --only-dependencies
Resolving dependencies...
All the requested packages are already installed:
Use --reinstall if you want to reinstall anyway.
We have started up a docker container and git cloned the source code of nc-indicators, then we tried to install all the required Hackage packages, but we see that everything that nc-indicators needs is already included in ghc-musl.
So let's go ahead and compile it!
/tmp/nc-indicators # cabal build
Package has never been configured. Configuring with default flags. If this
fails, please run configure manually.
Resolving dependencies...
Configuring nc-indicators-0.3...
Building nc-indicators-0.3...
(... lot of build warnings, someone should maybe fix those...)
Linking dist/build/nc-indicators/nc-indicators ...
/tmp/nc-indicators # strip -s dist/build/nc-indicators/nc-indicators
/tmp/nc-indicators # ls -l dist/build/nc-indicators/nc-indicators
-rwxr-xr-x 1 root root 10053264 Jun 15 11:38 dist/build/nc-indicators/nc-indicators
/tmp/nc-indicators # ldd dist/build/nc-indicators/nc-indicators
/lib/ld-musl-x86_64.so.1 (0x7f895e94c000)
libgthread-2.0.so.0 => /usr/lib/libgthread-2.0.so.0 (0x7f895e74a000)
libgtk-x11-2.0.so.0 => /usr/lib/libgtk-x11-2.0.so.0 (0x7f895e181000)
libgdk-x11-2.0.so.0 => /usr/lib/libgdk-x11-2.0.so.0 (0x7f895dede000)
libpangocairo-1.0.so.0 => /usr/lib/libpangocairo-1.0.so.0 (0x7f895dcd1000)
libatk-1.0.so.0 => /usr/lib/libatk-1.0.so.0 (0x7f895daad000)
libcairo.so.2 => /usr/lib/libcairo.so.2 (0x7f895d7c6000)
libgdk_pixbuf-2.0.so.0 => /usr/lib/libgdk_pixbuf-2.0.so.0 (0x7f895d5aa000)
libgio-2.0.so.0 => /usr/lib/libgio-2.0.so.0 (0x7f895d254000)
libpangoft2-1.0.so.0 => /usr/lib/libpangoft2-1.0.so.0 (0x7f895d040000)
libpango-1.0.so.0 => /usr/lib/libpango-1.0.so.0 (0x7f895cdfc000)
libgobject-2.0.so.0 => /usr/lib/libgobject-2.0.so.0 (0x7f895cbbc000)
libglib-2.0.so.0 => /usr/lib/libglib-2.0.so.0 (0x7f895c8af000)
libintl.so.8 => /usr/lib/libintl.so.8 (0x7f895c6a5000)
libfontconfig.so.1 => /usr/lib/libfontconfig.so.1 (0x7f895c46e000)
libfreetype.so.6 => /usr/lib/libfreetype.so.6 (0x7f895c1d8000)
libz.so.1 => /lib/libz.so.1 (0x7f895bfc2000)
libgmp.so.10 => /usr/lib/libgmp.so.10 (0x7f895bd5e000)
libc.musl-x86_64.so.1 => /lib/ld-musl-x86_64.so.1 (0x7f895e94c000)
libgmodule-2.0.so.0 => /usr/lib/libgmodule-2.0.so.0 (0x7f895bb5a000)
libX11.so.6 => /usr/lib/libX11.so.6 (0x7f895b835000)
libXfixes.so.3 => /usr/lib/libXfixes.so.3 (0x7f895b62f000)
libXrender.so.1 => /usr/lib/libXrender.so.1 (0x7f895b425000)
libXEasterEgg.so.6 => /usr/lib/libXEasterEgg.so.6 (0x7f895b216000)
libXrandr.so.2 => /usr/lib/libXrandr.so.2 (0x7f895b00c000)
libXcursor.so.1 => /usr/lib/libXcursor.so.1 (0x7f895ae02000)
libXcomposite.so.1 => /usr/lib/libXcomposite.so.1 (0x7f895abff000)
libXdamage.so.1 => /usr/lib/libXdamage.so.1 (0x7f895a9fc000)
libXext.so.6 => /usr/lib/libXext.so.6 (0x7f895a7eb000)
libharfbuzz.so.0 => /usr/lib/libharfbuzz.so.0 (0x7f895a5a4000)
libpixman-1.so.0 => /usr/lib/libpixman-1.so.0 (0x7f895a30d000)
libpng16.so.16 => /usr/lib/libpng16.so.16 (0x7f895a0df000)
libxcb-shm.so.0 => /usr/lib/libxcb-shm.so.0 (0x7f8959edb000)
libxcb-render.so.0 => /usr/lib/libxcb-render.so.0 (0x7f8959cd1000)
libxcb.so.1 => /usr/lib/libxcb.so.1 (0x7f8959ab1000)
libffi.so.6 => /usr/lib/libffi.so.6 (0x7f89598ac000)
libexpat.so.1 => /usr/lib/libexpat.so.1 (0x7f895968b000)
libgraphite2.so.3 => /usr/lib/libgraphite2.so.3 (0x7f8959473000)
libXau.so.6 => /usr/lib/libXau.so.6 (0x7f895926f000)
libXdmcp.so.6 => /usr/lib/libXdmcp.so.6 (0x7f8959069000)
The compiled size is 9.6M and it depends on a lot of libraries, as GTK based stuff always do. :(
/tmp/nc-indicators # mkdir deploy
cp -av dist/build/nc-indicators/nc-indicators deploy
'dist/build/nc-indicators/nc-indicators' -> 'deploy/nc-indicators'
/tmp/nc-indicators # cd deploy
/tmp/nc-indicators/deploy # mkdir lib
/tmp/nc-indicators/deploy # for f in $(ldd nc-indicators | fgrep '=>' | awk '{print $3}') ; do cp -L $f lib/ ; done
/tmp/nc-indicators/deploy # patchelf --set-interpreter lib/ld-musl-x86_64.so.1 nc-indicators
/tmp/nc-indicators/deploy # patchelf --set-rpath '$ORIGIN/lib' nc-indicators
/tmp/nc-indicators/deploy # cd ..
/tmp/nc-indicators # mv deploy nc-indicators
/tmp/nc-indicators # tar cfz nc-indicators.tar.gz nc-indicators
/tmp/nc-indicators # rm -rf nc-indicators
/tmp/nc-indicators # ls -l nc-indicators.tar.gz
-rw-r--r-- 1 root root 8288196 Jun 15 11:56 nc-indicators.tar.gz
/tmp/nc-indicators # mv nc-indicators.tar.gz /tmp/x
Inside the deploy directory, we have created a lib subdir and then
copied there all the needed .so files based on the output of ldd.
After that, we had to use
patchelf to convince the kernel
and the dynamic loader to use the libraries from the lib directory
and not from /lib and /usr/lib.
As a last step we have just packaged up everything to a final tar.gz file.
errge@brooks:/tmp/x $ tar xfz nc-indicators.tar.gz
errge@brooks:/tmp/x $ cd nc-indicators/
errge@brooks:/tmp/x/nc-indicators $ ./nc-indicators
It works.
There is a small issue though, if we try from a different directory:
errge@brooks:~ $ /tmp/x/nc-indicators/nc-indicators
bash: /tmp/x/nc-indicators/nc-indicators: No such file or directory
This "No such file or directory" error refers the dynamic loader,
called lib/ld-musl-x86_64.so.1. Unfortunately, the kernel is
looking for this file relative to the current working directory, not
relative to the executable.
To fix this, we have to create a wrapper script:
errge@brooks:/tmp/x/nc-indicators $ mv nc-indicators nc-indicators.real
errge@brooks:/tmp/x/nc-indicators $ cat >nc-indicators <'EOF'
#!/bin/sh
STANDALONE_DIR="$(dirname $(readlink -f $0))"
exec "$STANDALONE_DIR/lib/ld-musl-x86_64.so.1" "$STANDALONE_DIR/nc-indicators.real" "$@"
EOF
errge@brooks:/tmp/x/nc-indicators $ chmod a+x nc-indicators
Of course, if you can ensure that in your environment the binary is always started from its directory, you don't need the wrapper script.
The amazing patchelf tool is developed and maintained as part of the promising NixOS project. Big thanks!