Lubuntu v. 26.4 Laptop ACER Aspire One 725 4GB RAM.
Installed and everything worked great until I tried to install updates then the system stalled. I waited 30 mins plus and it stayed locked. Had to force a shut down.
Welcome to Ubuntu Discourse 
Please open a terminal and run this command:
sudo apt update
Post any error messages, usually at the end, between preformatted text (highlight output and click on the </> icon in the composer or use Ctlr+E on the keyboard.
How much of that RAM was already in use when trying to install the updates? Even though Lubuntu has the smallest memory footprint of all the flavors, you still need to be frugal in your application usage; no tab orgies in Firefox, for instance.
You can get a rough estimate of memory usage with this command:
free -htv
Iāve had Ubuntu live sessions lockup the way you describe ā just frozen solid ā and the cause was running out of RAM. Such a condition in the wrong phase of apt upgrade can have dire consequences as a friend of mine found out when the release upgrader crashed mid flight ā that was a fun weekend. 
No other programs were running.
free -htv gives
grainne@grainne-ao725:\~$ free -htv
total used free shared buff/cache available
Mem: 3.5Gi 868Mi 1.9Gi 10Mi 1.0Gi 2.7Gi
Swap: 511Mi 0B 511Mi
Total: 4.0Gi 868Mi 2.4Gi
Comm: 2.3Gi 2.3Gi -37Mi
grainne@grainne-ao725:\~$
Please put all log and other console/terminal output in pre-formatted code blocks (click the </> icon in the editor first and paste into the new element). That output is virtually illegible; alignment is off.
See items 4 and 5 in the Posting Guide.
Optional helper script
If you are so inclined, I took it upon myself to provide a little helper script for that. 
1 Like
Thanks for editing your post; much better!
That should be enough, I think. I know the chance is slim and the the error should not manifest as hard lockup, but is there enough storage space available for all the package upgrades?
Assuming there is, letās see if at least some log messages made it to the storage device before the crash. You should start by looking in /var/log/apt/term.log. That file usually contains the terminal output of the last APT actions; if nothing else it should help narrow down the time window for a more thorough log search:
journalctl -p err --no-pager --since=<apt log start> --until=<rough power-off time>
You should be able to just reuse the date string from the last āLog started:ā line in term.log.
(Itās probably easier to just pipe the output directly to the system clipboard: journalctl <args> | wl-copy; might need sudo apt install wl-clipboard)
I almost forgot, I have very old memories of inexplicable hard lockups when I still had NVIDIA GPUās with their dreadful proprietary drivers. I never could 
NVIDIA for that, but I havenāt had one of those ever since I stopped using their hardware. Not saying it is your NVIDIA GPU ā you havenāt shared anything much about your hardware, after all ā but if we donāt find something in the logs, Iāll be more inclined to. 
BTW, hardware specs, please, preferably in some of those nice code blocks. 
inxi -b
That should do for a start.
Thanks Peter,
After trying a couple more distros, whose updates worked ok, I installed a newly downloaded Lubuntu. Updates now working ok. Firefox is a bit slow even though I have fibre. Is my machine too old?
Anyway here is a copy on inxi -b
grainne@grainne-ao725:~$ inxi -b System: Host: grainne-ao725 Kernel: 7.0.0-22-generic arch: x86_64 bits: 64 Desktop: LXQt v: 2.3.2 Distro: Lubuntu 26.04 LTS (Resolute Raccoon) Machine: Type: Laptop System: Acer product: AO725 v: V2.04 serial: Mobo: Acer model: ZA10_BZ v: Type2 - A01 Board Version serial: Firmware: UEFI-[Legacy] vendor: Insyde v: 2.04 date: 09/06/2012 Battery: ID-1: BAT1 charge: 17.3 Wh (60.6%) condition: 28.6/37 Wh (77.2%) CPU: Info: dual core AMD C-70 APU with Radeon HD Graphics [MCP] speed (MHz): avg: 998 min/max: 800/1000 Graphics: Device-1: Advanced Micro Devices [AMD/ATI] Wrestler [Radeon HD 7290] driver: radeon v: kernel Device-2: Chicony HD WebCam driver: uvcvideo type: USB Display: x11 server: X.Org v: 21.1.22 driver: X: loaded: radeon unloaded: fbdev,modesetting,vesa dri: r600 gpu: radeon resolution: 1366x768~60Hz API: OpenGL v: 4.6 compat-v: 4.5 vendor: mesa v: 26.0.3-1ubuntu1 renderer: AMD PALM (DRM 2.51.0 / 7.0.0-22-generic) Info: Tools: api: eglinfo,glxinfo de: kscreen-doctor x11: xdriinfo, xdpyinfo, xprop, xrandr Network: Device-1: Realtek RTL810xE PCI Express Fast Ethernet driver: r8169 Device-2: Broadcom BCM4313 802.11bgn Wireless Network Adapter driver: bcma-pci-bridge Drives: Local Storage: total: 223.57 GiB used: 22.06 GiB (9.9%) Info: Memory: total: 4 GiB note: est. available: 3.52 GiB used: 1.5 GiB (42.6%) Processes: 173 Uptime: 18m Shell: Bash inxi: 3.3.40 grainne@grainne-ao725:~$
I have used the </> for the above but not sure it worked.
Another problem has just arisen when I load the software manager (Discover). I get error
Denis spaarks@gmail.com 12:04 (1 minute ago) to me W: Repositories should provide a clear-signed InRelease file, but none found at file:/cdrom/dists/resolute/InRelease. E: The repository āfile:/cdrom resolute Releaseā no longer has a Release file. W: Updating from such a repository canāt be done securely, and is therefore disabled by default. W: See apt-secure(8) manpage for repository creation and user configuration details. E: file:/cdrom resolute Release is not (yet) available (File not found - /cdrom/dists/resolute/Release (2: No such file or directory))