Skip to content

Instantly share code, notes, and snippets.

@cpsubrian
Last active December 6, 2023 11:03
Show Gist options
  • Save cpsubrian/3aa40f6f3d6ce2c707b9d8e34c652dcf to your computer and use it in GitHub Desktop.
Save cpsubrian/3aa40f6f3d6ce2c707b9d8e34c652dcf to your computer and use it in GitHub Desktop.
Compile Xvfb for AWS Lamba

Compile Xvfb for lambda.

Referenes

Based on the following guide: https://ericdraken.com/running-xvfb-on-a-shared-host-without-x/

Using the following docker image: https://hub.docker.com/r/lambci/lambda/

Start up and attach to docker container to do the build on

It's an Amazon Linux image that matches the environment of Lambda tasks.

# On my Mac, from the directory where I'll be working on my lambda function.
$ docker run -v "$PWD":/var/task -it lambci/lambda:build bash
# bash-4.2#

Install Xvfb and some other dependencies

We'll need some utils that it comes with.

$ yum install xorg-x11-server-Xvfb.x86_64 wget

Download xorg-server source code and unpack

$ cd /tmp
$ wget https://www.x.org/releases/X11R7.7/src/xserver/xorg-server-1.12.2.tar.gz
$ tar -xvf xorg-server-1.12.2.tar.gz
$ cd xorg-server-1.12.2

Modify some files for keymap compiling.

Edit xkb/xkbInit.c at line 754 in XkbProcessArguments()

        return 2;
    }

    // ADDED - Change xkbcomp bin directory with an environment variable
    char *xkbBinDir = getenv("XKB_BINDIR");
    if (xkbBinDir) {
        XkbBinDirectory = Xstrdup(xkbBinDir);
    }

    // ADDED - Change base xkb directory with an environment variable
    char *xkbBaseDir = getenv("XKBDIR");
    if (xkbBaseDir) {
        XkbBaseDirectory = Xstrdup(xkbBaseDir);
    }

    return 0;
}

Edit xkb/ddxLoad.c at line 188 in XkbDDXCompileKeymapByNames()

    const char *emptystring = "";
    char *xkbbasedirflag = NULL;
    const char *xkbbindir = emptystring;
    const char *xkbbindirsep = emptystring;

#ifdef WIN32
    char tmpname[PATH_MAX];
    const char *xkmfile = tmpname;
#else
    // MODIFICATION - Now using 'default.xkm' file to satisfy xkbcomp
    // const char *xkmfile = "-";
    const char *xkmfile = "default.xkm";
#endif

Create default.xkb

Contents for default.xkb:

xkb_keymap "default" {
    xkb_keycodes             { include "evdev+aliases(qwerty)" };
    xkb_types                { include "complete" };
    xkb_compatibility        { include "complete" };
    xkb_symbols              { include "pc+us+inet(evdev)" };
    xkb_geometry             { include "pc(pc105)" };
};

Create and compile it:

$ cd /tmp
$ vim default.xkb
# Insert contents above and save
$ xkbcomp -xkm default.xkb

Copy it into your lambda function /lib

$ mkdir /var/task/lib
$ cp default.xkm /var/task/lib

Install devel dependencies

$ yum install pixman-devel.x86_64 \
    libdrm-devel.x86_64 \
    libX11-devel.x86_64 \
    mesa-libGL-devel.x86_64 \
    openssl-devel.x86_64 \
    xorg-x11-xtrans-devel.noarch \
    libxkbfile-devel.x86_64 \
    libXfont-devel.x86_64 \
    libpciaccess-devel.x86_64 \
    xcb-util-keysyms-devel.x86_64

Configure and Make

$ ./configure
$ make

Copy Xvfb to lambda lib

$ cp hw/vfb/Xvfb /var/task/lib

In a new terminal, boot up another docker mounted to our task dir

# cd (your task directory)
$ docker run -v "$PWD":/var/task -it lambci/lambda:build bash

Check that we have any linked libs

Looks ok?

$ ls -la /var/task/lib
total 10812
drwxr-xr-x 5 root root      170 Dec  2 23:55 .
drwxr-xr-x 4 root root      136 Dec  2 23:28 ..
-rw-r--r-- 1 root root      314 Dec  2 23:43 default.xkb
-rw-r--r-- 1 root root    11248 Dec  2 23:43 default.xkm
-rwxr-xr-x 1 root root 11054660 Dec  2 23:55 Xvfb

$ cd /var/task/lib

$ ldd ./Xvfb
  linux-vdso.so.1 =>  (0x00007ffdc6f1a000)
  libcrypto.so.10 => /lib64/libcrypto.so.10 (0x00007f10f11ca000)
  libdl.so.2 => /lib64/libdl.so.2 (0x00007f10f0fc5000)
  libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f10f0da9000)
  libpixman-1.so.0 => /usr/lib64/libpixman-1.so.0 (0x00007f10f0afe000)
  libXfont.so.1 => /usr/lib64/libXfont.so.1 (0x00007f10f08c9000)
  libXau.so.6 => /usr/lib64/libXau.so.6 (0x00007f10f06c6000)
  libm.so.6 => /lib64/libm.so.6 (0x00007f10f03c4000)
  libc.so.6 => /lib64/libc.so.6 (0x00007f10f0001000)
  libz.so.1 => /lib64/libz.so.1 (0x00007f10efdeb000)
  /lib64/ld-linux-x86-64.so.2 (0x000056118b113000)
  libfreetype.so.6 => /usr/lib64/libfreetype.so.6 (0x00007f10efb4f000)
  libfontenc.so.1 => /usr/lib64/libfontenc.so.1 (0x00007f10ef947000)

Try to start Xvfb

First, set the environment variables for keymap:

$ export XKB_BINDIR=/usr/bin
$ export XKBDIR=/var/task/lib

Fails with keymap error.

$ ./Xvfb :99
[dix] Could not init font path element /usr/share/fonts/X11/misc/, removing from list!
[dix] Could not init font path element /usr/share/fonts/X11/TTF/, removing from list!
[dix] Could not init font path element /usr/share/fonts/X11/OTF/, removing from list!
[dix] Could not init font path element /usr/share/fonts/X11/Type1/, removing from list!
[dix] Could not init font path element /usr/share/fonts/X11/100dpi/, removing from list!
[dix] Could not init font path element /usr/share/fonts/X11/75dpi/, removing from list!
XKB: Failed to compile keymap
Keyboard initialization failed. This could be a missing or incorrect setup of xkeyboard-config.

Things I'm not sure about

  1. I assume the target machine needs XKBDIR and XKB_BINDIR, but since the machine in question doesn't have X11, it doesn't have xkbcomp, so does that mean I need to compile that from source also?
  2. Font errors above, not sure about that.
@princefishthrower
Copy link

princefishthrower commented Dec 10, 2022

@san-kumar - While Xfvb indeed starts running on a lambda environment, I'm finding that windows are never produced (i.e. running xwininfo -root -tree lists no child windows). However, an identical docker image ran anywhere else works fine, I see all the different windows of the applications I open as expected. Very strange and frustrating, I guess it has something to do with the restrictions of the lambda environment. Have you found the same or does your Ubuntu 16 image there work fine?

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment