change name to voidnsrun, add command-line arguments, rewrite readme

gch1p · Nov 29, 2020 · e42df36 · e42df36
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diff --git a/Makefile b/Makefile
@@ -1,13 +1,13 @@
 CC := gcc
 
-PROGRAM = glibcrun
+PROGRAM = voidnsrun
 CFLAGS  = -O2 -std=c99 -Wall -W
 LDFLAGS =
 
 INSTALL = /usr/bin/env install
 PREFIX	= /usr/local
 
-OBJS = glibcrun.o
+OBJS = voidnsrun.o
 
 all: $(PROGRAM)
 

diff --git a/README.md b/README.md
@@ -1,58 +1,117 @@
-# glibcrun
+# voidnsrun
 
-`glibcrun` is utility for launching glibc linked binaries in isolated namespaces
-in musl-libc Void Linux installations.
+`voidnsrun` is utility for launching programs in an isolated namespace with
+alternative `/usr` tree. Its primary goal is to run glibc-linked binaries in
+musl-libc Void Linux environments or vice-versa.
 
-It creates new private mount namespace for the running process, "replacing" `/usr`
-and `/var/db/xbps` with directories from your glibc basedir using bind
-mounts, and launches your glibc program.
+It creates a new private mount namespace, transparently substitutes `/usr` and 
+some other directories with directories from your alternative root using bind
+mounts, and launches your program.
 
-## Creating glibc chroot
+## Installation
 
-I will use `/glibc` directory name for an example, you can use any other path you
-want.
+Just clone the repo, and then:
 
 ```
-# mkdir /glibc
-# XBPS_ARCH=x86_64 xbps-install --repository=http://alpha.de.repo.voidlinux.org/current -r /glibc -S base-voidstrap
+$ make
+$ sudo make install
 ```
 
-When it's done you may want to chroot into it, e.g. to install some dependencies
-for your glibc software.
+Note that installed binary must be owned by root and have suid bit. `make install`
+should handle it.
 
-## Installing glibcrun
+## Usage
 
-Just clone the repo, and then:
+```
+voidnsrun [OPTIONS] [PROGRAM [ARGS]]
+
+Options:
+	-h:        print this help
+	-m <path>: add bind mount
+	-r <path>: altroot path. If this option is not present,
+	           VOIDNSRUN_DIR environment variable is used.
+	-v:        print version
+```
+
+`voidnsrun` needs to know the path to your alternative root directory and it can
+read it from the `VOIDNSRUN_DIR` environment variable or you can use `-r`
+argument to specify it.
+
+You may want to add something like this to your `~/.bashrc` or similar script:
 
 ```
-$ make
-$ sudo make install
+export VOIDNSRUN_DIR=/glibc
 ```
 
-Note that installed binary must be owned as root and have suid bit. `make install`
-should handle it, but  anyway.
+By default, `voidnsrun` binds these paths from alternative root to the new
+namespace:
+- `/usr`
+- `/var/db/xbps`
+- `/etc/xbps.d`
 
-## Usage
+If you want to mount something else, use `-m` argument.
+
+## Example
 
-`glibcrun` needs to know the path to your glibc base directory and it reads it from
-the `GLIBCRUN_DIR` environment variable. You may want to add something like this
-to your `~/.bashrc` or similar script:
+Let's imagine you want to use some proprietary glibc-linked app on your
+musl-libc Void Linux box. Let it be Vivaldi browser for the example. You
+unpacked it to `/opt/vivaldi` and it doesn't work, obviously.
 
+First, you need to perform an alternative glibc base system installation to a
+separate new directory:
 ```
-export GLIBCRUN_DIR=/glibc
+# mkdir /glibc
+# XBPS_ARCH=x86_64 xbps-install --repository=http://alpha.de.repo.voidlinux.org/current -r /glibc -S base-voidstrap
+```
+
+Export path to this installation for `voidnsrun`:
+```
+export VOIDNSRUN_DIR=/glibc
 ```
 
-When `glibcrun` is run without arguments it will attempt to launch a shell from your
-`SHELL` variable, otherwise it will treat the first argument as a path to an executable
-and the rest as a list of arguments.
+Try launching your app:
+```
+voidnsrun /opt/vivaldi/vivaldi
+```
 
-Example:
+It won't work just yet:
+```
+/opt/vivaldi/vivaldi: error while loading shared libraries: libgobject-2.0.so.0: cannot open shared object file: No such file or directory
+```
+
+Now you need to install all its dependencies into your glibc installation. Use
+`xlocate` from `xtools` package to find a package responsible for a file (or
+just guess it):
+```
+$ xlocate libgobject-2.0.so.0
+Signal-Desktop-1.38.1_1	/usr/lib/signal-desktop/resources/app.asar.unpacked/node_modules/sharp/vendor/lib/libgobject-2.0.so -> /usr/lib/signal-desktop/resources/app.asar.unpacked/node_modules/sharp/vendor/lib/libgobject-2.0.so.0.5600.4
+Signal-Desktop-1.38.1_1	/usr/lib/signal-desktop/resources/app.asar.unpacked/node_modules/sharp/vendor/lib/libgobject-2.0.so.0 -> /usr/lib/signal-desktop/resources/app.asar.unpacked/node_modules/sharp/vendor/lib/libgobject-2.0.so.0.5600.4
+Signal-Desktop-1.38.1_1	/usr/lib/signal-desktop/resources/app.asar.unpacked/node_modules/sharp/vendor/lib/libgobject-2.0.so.0.5600.4
+glib-2.66.2_1	/usr/lib/libgobject-2.0.so.0 -> /usr/lib/libgobject-2.0.so.0.6600.2
+glib-2.66.2_1	/usr/lib/libgobject-2.0.so.0.6600.2
+glib-devel-2.66.2_1	/usr/share/gdb/auto-load/usr/lib/libgobject-2.0.so.0.6600.2-gdb.py
+libglib-devel-2.66.2_1	/usr/lib/libgobject-2.0.so -> /usr/lib/libgobject-2.0.so.0
+```
+
+Sync repos and install `glib`. You can use `voidnsrun` for this purpose too.
+Also, I think you should bind `/etc` and `/var` while using `xbps-install` via
+`voidnsrun`, to not mess with your main system files.
+```
+$ sudo voidnsrun -r /glibc -m /etc -m /var xbps-install -Su
+$ sudo voidnsrun -r /glibc -m /etc -m /var xbps-install glib
+```
 
+Try launching vivaldi again:
 ```
-glibcrun /opt/palemoon/palemoon -ProfileManager
+$ voidnsrun /opt/vivaldi/vivaldi
+/opt/vivaldi/vivaldi: error while loading shared libraries: libnss3.so: cannot open shared object file: No such file or directory
 ```
 
-will launch `/opt/palemoon/palemoon -ProfileManager`.
+As you can see, it no longer complains about missing `libgobject-2.0.so.0`, now 
+it's `libnss3.so`. Repeat steps above for all missing dependencies, and in the
+end, it will work. (If it's not, then something's still missing. In particular,
+make sure to install fonts related packages: `xorg-fonts`, `freetype`,
+`fontconfig`, `libXft`.)
 
 ## License
 

diff --git a/glibcrun.c b/glibcrun.c