Where is the memtest option on the Ubuntu 64-bit live CD?
Memtest86+
If you boot your computer in BIOS mode (alias CSM alias legacy mode), memtest86+ works.
But if you boot your computer in UEFI mode, memtest86+ will not work, because it is a 16-bit program.
www.memtest.org
Memtest86
The original branch, memtest86 (without plus), works in UEFI mode. There is a free version (but I don't think it is open source, and for this reason not available to include in linux distros).
www.memtest86.com
Memtest via Ubuntu's boot menu
Memtest86+ is included in most Ubuntu iso files, for example
ubuntu-16.04.1-desktop-amd64.iso
There is an option 'Test memory', when you boot your computer in BIOS mode (alias CSM alias legacy mode) from a DVD disk or USB pendrive with a cloned copy from the iso file.
In Ubuntu 16.04.x LTS systems installed in BIOS mode, there are also options 'Test memory', when you boot your computer (via the grub menu).
But when you boot your computer in UEFI mode, there is no option to use Memtest86+ (because it would not work).
Standalone Memtest86+ image file
If you have an old version of Memtest86+, you can test 4 GiB of RAM. If you have more than 4 GiB RAM in your computer, you need version 5.01 or newer.
Enhancements in v5.01 :
- Added support for up to 2 TB of RAM on X64 CPUs
(In September 2020 there is also a beta version, 5.31b.)
You may want a small standalone Memtest86+ iso file or other image file in order to create a live USB drive.
I did not find any file at www.memtest.org/#downiso, that is easy to install to USB in linux. The iso file 'memtest86+-5.01.iso' is not a hybrid iso file and cannot be made into one.
$ isohybrid memtest86+-5.01.iso
isohybrid: memtest86+-5.01.iso: unexpected boot catalogue parameters
It is a very barebone iso file. I tested in VirtualBox, and it works as a CD.
But there is an 'Auto-installer for USB Key (Win 9x/2k/xp/7)' at
www.memtest.org/download/5.01/memtest86+-5.01.usb.installer.zip
I extracted it to a USB pendrive in Windows and cloned this system to a compressed image file and uploaded it to
dd_memtest-plus-5.01_33M.img.xz
$ md5sum dd_memtest-plus-5.01_33M.img.xz
7f91882ab90df13a938749176a0ff4c4 dd_memtest-plus-5.01_33M.img.xz
which can be extracted directly in linux by mkusb, dus and Disks alias gnome-disks (and in two steps, extracting and cloning, with other cloning tools, that accept the extracted file as an input file).
After installing mkusb and/or dus, you can do it via Dash or the menu entry or with the following command line
dus dd_memtest-plus-5.01_33M.img.xz
According to this bug report comment 2 and 3 state:
- The EFI version of grub does not support loading real mode binaries.
- Don't present the GRUB menu option on EFI systems, since it won't work (see LP #883017).
So from the live cd it will not work at the moment. According to this topic you can add it afterwards: How can I add the Memtest86+ options back to the Grub menu? but I doubt it will work: deleted comments state you still get the Error unknown command Linux16 error.
I also found this:
The issue is not 16 or 32 bits boot protocol, the main issue is the numerous BIOS calls required to do the memory initialization. EFI is a nice idea, but the first time I heard "EFI will replace BIOS in the upcoming months !!!" was in 2002 at an Intel Developer's forum. 10 years after, UEFI replaced EFI but BIOS is still present in 99% of PC Motherboard. It's an hard task to build an EFI-readyMemtest86+, with massive code rewrite, and that version will not be compatible with legacy BIOS. I will not consider supporting two forks at the same time, so when Memtest86+ will switch to EFI, the BIOS version will be discontinued. When BIOS will be not be available in standard PC components, I'll start working on en EFI revision.
A beta version of the proprietary PassMark MemTest86 5.0 for EFI is now available:
http://www.memtest86.com/download.htm
This should be launchable from GRUB, rEFInd, gummiboot, etc., although you may need to explicitly add a menu entry to do so. (This obviously hasn't yet been built into shipping distributions as I write.)