LinuxCNC Documentation

Updating LinuxCNC to a new minor release (ie to a new version in the same stable series, for example from 2.9.7 to 2.9.8) is an automatic process if your PC is connected to the internet. You will see an update prompt after a minor release along with other software updates. If you don’t have an internet connection to your PC see Updating without Network.

1. Upgrade to the new version

This section describes how to upgrade LinuxCNC from version 2.8.x to a 2.9.y version. It assumes that you have an existing 2.8 install that you want to update.

To upgrade LinuxCNC from a version older than 2.8, you have to first upgrade your old install to 2.8, then follow these instructions to upgrade to the new version.

If you do not have an old version of LinuxCNC to upgrade, then you’re best off making a fresh install of the new version as described in the section Getting LinuxCNC.

Furthermore, if you are running Ubuntu Precise, Debian Wheezy or Debian Buster it is well worth considering making a backup of the "linuxcnc" directory on removable media and performing a clean install of a newer OS and LinuxCNC version as these releases were EOL in 2017, 2018 and 2022 respectively. If you are running on Ubuntu Lucid then you will have to do this, as Lucid is no longer supported by LinuxCNC (it was EOL in 2013).

To upgrade major versions like 2.8 to 2.9 when you have a network connection at the machine you need to disable the old linuxcnc.org apt sources in the file /etc/apt/sources.list and add a new linuxcnc.org apt source for 2.9, then upgrade LinuxCNC.

The details will depend on which platform you’re running on. Open a terminal then type lsb_release -ic to find this information out:

lsb_release -ic
Distributor ID: Debian
Codename:       Trixie

You should be running on Debian Bullseye, Bookworm or Trixie or Ubuntu 20.04 "Focal Fossa" or newer. LinuxCNC 2.9.y will not run on older distributions than these.

You will also need to check which realtime kernel is being used:

uname -r
6.1.0-10-rt-amd64

If you see (as above) -rt- in the kernel name then you are running the preempt-rt kernel and should install the "uspace" version of LinuxCNC. You should also install uspace for "sim" configs on non-realtime kernels.

If you see -rtai- in the kernel name then you are running RTAI realtime. See below for the LinuxCNC version to install. RTAI packages are available for Bookworm and Buster but not currently for Bullseye.

1.1. Apt Sources Configuration

  • Open the Software Sources window. The process for doing this differs slightly on the three supported platforms:

    • Debian:

      • Click on Applications Menu, then System, then Synaptic Package Manager.

      • In Synaptic, click on the Settings menu, then click Repositories to open the Software Sources window.

    • Ubuntu Precise:

      • Click on the Dash Home icon in the top left.

      • In the Search field, type "software", then click on the Ubuntu Software Center icon.

      • In the Ubuntu Software Center window, click on the Edit menu, then click on Software Sources... to open the Software Sources window.

    • Ubuntu Lucid:

      • Click the System menu, then Administration, then Synaptic Package Manager.

      • In Synaptic, click on the Settings menu, then click on Repositories to open the Software Sources window.

  • In the Software Sources window, select the Other Software tab.

  • Delete or un-check all the old linuxcnc.org entries (leave all non-linuxcnc.org lines as they are).

  • Click the Add button and add a new apt line. The line will be slightly different on the different platforms:

Table 1. Tabular overview on variants of the Operating System and the corresponding configuration of the repository. The configuration can be performed in the GUI of the package manager or in the file /etc/apt/sources.list.
OS / Realtime Version Repository

Debian Bullseye - preempt

deb https://linuxcnc.org bullseye base 2.9-uspace

Debian Bookworm - preempt

deb https://linuxcnc.org bookworm base 2.9-uspace

Debian Bookworm - RTAI

deb https://linuxcnc.org bookworm base 2.9-rt

Debian Trixie - preempt

deb https://linuxcnc.org trixie base 2.9-uspace

Debian Trixie - RTAI

deb https://linuxcnc.org trixie base 2.9-rt
Setting apt sources
Figure 1. Figure with a screenshot of the repository configuration of the synaptic package manager.

  • Click Add Source, then Close in the Software Sources window. If it pops up a window informing you that the information about available software is out-of-date, click the Reload button.

1.2. Upgrading to the new version

Now your computer knows where to get the new version of the software, next we need to install it.

The process again differs depending on your platform.

1.2.1. Debian Bullseye, Bookworm and Trixie

Debian uses the Synaptic Package Manager.

  • Open Synaptic using the instructions in Setting apt sources above.

  • Click the Reload button.

  • Use the Search function to search for linuxcnc.

  • The package is called "linuxcnc" for RTAI kernels and "linuxcnc-uspace" for preempt-rt.

  • Click the check box to mark the new linuxcnc and linuxcnc-doc-* packages for upgrade. The package manager may select a number of additional packages to be installed, to satisfy dependencies that the new linuxcnc package has.

  • Click the Apply button, and let your computer install the new package. The old linuxcnc package will be automatically upgraded to the new one.

1.3. Ubuntu

  • Click on the Dash Home icon in the top left.

  • In the Search field, type "update", then click on the Update Manager icon.

  • Click the Check button to fetch the list of packages available.

  • Click the Install Updates button to install the new versions of all packages.

2. Updating without Network

To update without a network connection you need to download the .deb then install it with dpkg. The .debs can be found in https://linuxcnc.org/dists/ .

You have to drill down from the above link to find the correct deb for your installation. Open a terminal and type in lsb_release -ic to find the release name of your OS.

> lsb_release -ic
Distributor ID: Debian
Codename:       trixie

Pick the OS from the list then pick the major version you want like 2.9-rt for RTAI or 2.9-uspace for preempt-rt.

Next pick the type of computer you have: binary-amd64 for 64-bit PC or binary-arm64 (64bit) for Raspberry Pi.

Next pick the version you want from the bottom of the list like linuxcnc-uspace_2.9.8_amd64.deb (choose the latest by date). Download the deb and copy it to your home directory. You can rename the file to something a bit shorter with the file manager like linuxcnc_2.9.8.deb then open a terminal and install it with the package manager with this command:

sudo dpkg -i linuxcnc_2.9.8.deb

3. Updating Configuration Files for 2.9

3.1. Stricter handling of pluggable interpreters

If you just run regular G-code and you don’t know what a pluggable interpreter is, then this section does not affect you.

A seldom-used feature of LinuxCNC is support for pluggable interpreters, controlled by the undocumented [TASK]INTERPRETER INI setting.

Versions of LinuxCNC before 2.9.0 used to handle an incorrect [TASK]INTERPRETER setting by automatically falling back to using the default G-code interpreter.

Since 2.9.0, an incorrect [TASK]INTERPRETER value will cause LinuxCNC to refuse to start up. Fix this condition by deleting the [TASK]INTERPRETER setting from your INI file, so that LinuxCNC will use the default G-code interpreter.

3.2. Canterp

If you just run regular G-code and you don’t use the canterp pluggable interpreter, then this section does not affect you.

In the extremely unlikely event that you are using canterp, know that the module has moved from /usr/lib/libcanterp.so to /usr/lib/linuxcnc/canterp.so, and the [TASK]INTERPRETER setting correspondingly needs to change from libcanterp.so to canterp.so.

3.3. Spindle limits in the INI

It is now possible to add settings to the [SPINDLE] section of the INI file

MAX_FORWARD_VELOCITY = 20000 The maximum spindle speed (in rpm)

MIN_FORWARD_VELOCITY = 3000 The minimum spindle speed (in rpm)

MAX_REVERSE_VELOCITY = 20000 This setting will default to MAX_FORWARD_VELOCITY if omitted.

MIN_REVERSE_VELOCITY = 3000` This setting is equivalent to MIN_FORWARD_VELOCITY but for reverse spindle rotation. It will default to the MIN_FORWARD_VELOCITY if omitted.

INCREMENT = 200 Sets the step size for spindle speed increment / decrement commands. This can have a different value for each spindle. This setting is effective with AXIS and Touchy but note that some control screens may handle things differently.

HOME_SEARCH_VELOCITY = 100 - Accepted but currently does nothing

HOME_SEQUENCE = 0 - Accepted but currently does nothing

4. Updating Configuration Files for 2.10.y

Touchy: the Touchy MACRO entries should now be placed in a [MACROS] section of the INI rather than in the [TOUCHY] section. This is part of a process of commonising the INI setting between GUIs.

5. Preview renderer now requires OpenGL 3.3 core

The G-code preview shared by AXIS, the GTK screens (Gremlin / gmoccapy / gscreen / GladeVCP hal_gremlin / QtPlasmaC), and QtVCP was rewritten to use a single modern OpenGL 3.3 core-profile renderer (shaders, VBOs, an offscreen framebuffer for click selection, a glyph-atlas for overlay text). The legacy fixed-function path (display lists, immediate mode, GL_SELECT picking, glBitmap text, line stipple, GL_LIGHTING) has been removed. There is no runtime switch and no in-process fallback.

Hardware requirement. OpenGL 3.3 core is needed. On the supported platform (Linux with Mesa) this is available on Intel Sandy Bridge (2011) and newer, AMD r600 and newer, and nouveau. Machines without a capable GPU can use Mesa’s software renderer (llvmpipe), which handles the line-dominated preview acceptably:

LIBGL_ALWAYS_SOFTWARE=1 linuxcnc myconfig.ini

If a core context cannot be created the GUI exits at start-up with a diagnostic naming the OpenGL 3.3 requirement and suggesting LIBGL_ALWAYS_SOFTWARE=1, rather than starting with a blank or corrupt preview.

Warning
BREAKING: out-of-tree screens that inject raw legacy OpenGL

Custom screens that subclass the in-tree preview classes and override a drawing internal to emit raw fixed-function OpenGL (immediate mode, display lists, glBitmap, etc.) will fail against a core context. Compatibility is preserved only at the calling surface: the public methods and attributes of rs274.glcanon.GlCanonDraw / glnav.GlNavBase used by the in-tree GUIs keep their names, signatures, and behaviour (realize, redraw, redraw_perspective, redraw_ortho, select, set_highlight_line, set_canon, posstrs, the stale_dlist(...) cache-invalidation entry points, and the get_*/is_* callback contract). Move any custom drawing onto those supported entry points, or draw with your own modern-OpenGL code.

The immediate-mode drawing helpers used by the old renderer remain available for compatibility (linuxcnc.draw_lines, linuxcnc.line9, linuxcnc.draw_dwells, linuxcnc.positionlogger.call()); they are unused by the in-tree GUIs, which bake geometry to VBOs and upload the backplot from positionlogger.points(), but still work for out-of-tree tools under a legacy/compatibility context.

5.1. Notes for integrators and driver authors

  • AXIS / Togl. The vendored Togl widget (src/emc/usr_intf/axis/extensions/togl.c) gained a boolean -coreprofile option (default false). When true it creates the context with glXChooseFBConfig + glXGetVisualFromFBConfig
    glXCreateContextAttribsARB (OpenGL 3.3 core), raising a descriptive Tcl error on failure. AXIS always enables it. The default (false) path is unchanged, so vismach and any out-of-tree Togl users keep their legacy contexts.

  • Gremlin (GTK). GTK3 only hands out core contexts through GtkGLArea, so the gremlin widget still builds its context by hand via GLX, now requesting 3.3 core with glXCreateContextAttribsARB. PyOpenGL cannot resolve that extension entry point (it comes back as a null function), so gremlin loads libGL directly with ctypes and creates and binds the context (choose-fbconfig / make-current / swap) through that one handle to avoid mixing context pointers.

  • Line width in core profiles. A forward-compatible core context (Qt requests one) rejects glLineWidth(> 1) with GL_INVALID_VALUE even though GL_ALIASED_LINE_WIDTH_RANGE reports a larger maximum. The renderer probes the accepted width once and caches it, so thick lines (the selection highlight, dwell markers) degrade to 1 px on such drivers instead of raising; a non-forward-compatible core context (AXIS’s Togl, Gremlin’s GLX) keeps the wider lines. Thick lines via quad expansion are a possible future improvement.

  • vismach is unaffected: it keeps its legacy Togl context and immediate-mode drawing; only its camera consumes the (now GL-free) explicit matrices from glnav.

5.2. How the preview is put together

The drawing itself lives in lib/python/rs274/glcanon_scene.py, in four tiers. Nothing here changes what the preview looks like; it is where to start reading if you need to fix or extend one part of it.

  • Parts. One class per drawing concern - grid, program geometry, extents, bounding box, offsets, small origin, axes, machine-limits box, tool, live backplot, DRO overlay, the user_plot() hook. A part draws that one thing and nothing else. Adding a preview element means adding a part and placing it in the scene’s order, not editing an existing part.

  • The scene. PreviewScene holds the parts in draw order and runs them. Visibility is decided by the scene, not the part: it evaluates each part’s visible(ctx) and simply does not call a part whose gate is false, so draw() may assume it is visible and must not open with an if not shown: return. Gates that couple parts belong to the scene too - the extents-versus-bounding-box either/or, and the translucent compositing program_alpha wraps the program in.

  • Primitives. Services several parts share - a line array, a wireframe box, Hershey vector text, the tool-cone mesh - reached as ctx.prim. Letters are a primitive that axes, extents and offsets all use, not a sibling of "axes".

  • Passes. The preview is three sets of depth/blend state, not an arbitrary order: world geometry, translucent geometry drawn over it at equal depth, and the screen-space overlay. Each part declares its pass_; the scene sets the state when the pass changes. A part that needs something else for its own drawing (the tool’s constant-alpha blend) restores it afterwards.

Transforms go through a scoped model-view stack: with ctx.mv.push(): restores the previous transform on exit, including when an exception unwinds through it, so a part cannot leak a transform onto a later one. Offsets, small origin and axes share one such scope (RelativeCoordGroup), because the axes are drawn in the offset frame the offsets progressively build.

Parts read a FrameContext - an explicit, enumerated list of machine, view and renderer state, built once per frame by GlCanonDraw - rather than the widget itself. That is what lets them be tested without a window: build a context by hand, call part.draw(ctx), and assert on the vertices it emitted. See tests/glcanon-scene/.

Click-to-select is not a part - it draws nothing to the screen. Picker renders the same program geometry into an offscreen framebuffer with line numbers encoded as colour and resolves the nearest hit; GlCanonDraw.select(x, y) delegates to it. It shares one ProgramGeometry with the drawing part, so the pickable geometry and the drawn geometry cannot drift apart.

Setting GLCANON_SCENE_DEBUG=1 logs which parts the scene drew and which it skipped whenever that split changes, and reports depth/blend state a part left behind.

6. New HAL components

6.1. Non-Realtime

mdro mqtt-publisher pi500_vfd pmx485-test qtplasmac-cfg2prefs qtplasmac-materials qtplasmac-plasmac2qt qtplasmac-setup sim-torch svd-ps_vfd

6.2. Realtime

anglejog div2 enum filter_kalman flipflop homecomp limit_axis mesa_uart millturn scaled_s32_sums tof ton

7. New Drivers

A framework for controlling ModBus devices using the serial ports on many Mesa cards has been introduced. http://linuxcnc.org/docs/2.9/html/drivers/mesa_modbus.html

A new GPIO driver for any GPIO which is supported by the gpiod library is now included: http://linuxcnc.org/docs/2.9/html/drivers/hal_gpio.html