Re: [lubuntu-users] Support

2017-11-12 Thread Ian Bruntlett 
Hi Ralf,

On 12 November 2017 at 16:54, Ralf Mardorf 
wrote:

> Smartctl is not perfect, but another link in the chain, even unplugging
> SATA cables and connecting them again is important and so on and so
> forth...
>
On a system I refurbished recently, memtest86+ passed and dban failed. I
booted into a live CD, queried smartctl and was told everything was OK.
After some research I was told that modern hard drives tend to fail
suddenly.

I removed the hard drive, put a replacement in, installed lubuntu on it and
then used it on and off for a while as my final testing. It has now been
given to its new home.

Just running one test, especially the free as in beer Memtest release
> gains absolutely nothing, at least taking a look at /var/log,
> journalctl and Co in combination with software testing hardware and
> remounting, cleaning, etc. should be done. More experienced users could
> use coolant spray etc. ...
>

I agree - to a point - I have found memtest86+ to be useful - as the first
part of a testing process.

When I answered the previous question with info to run memtest86+, I was
not advocating _only_ running memtest86+, just that I believed it would be
helpful to run the test and that the questioner would be able to get back
to this list with the results and then people (such as yourself) could
offer further advice.

BW,


Ian

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Re: [lubuntu-users] Privacy and security - Was: Lubuntu's repository

2017-11-12 Thread Walter Lapchynski 


On November 11, 2017 10:35:58 PM PST, Ralf Mardorf  
wrote:
>to grant privacy and security it's important to check the ISO against a
>signed checksum by a trusted key.

Agreed. Nice solution. I'd put it under source control somewhere and/or add it 
to the Ubuntu wiki's documentation on the subject. 

However, you can't ensure security with the current script, as it uses the key 
short ID. Since it's based on an SHA1 hash, collisions are rather trivially 
created for the short ID and, to a lesser degree, the long ID. There are 
examples out there in the wild. That said, I'd ensure you use the full 40 
character fingerprint to get the key. 

Also, while you can't fix it, the unavailability of encrypted connections in 
the Ubuntu infrastructure (cdimage, keyserver) means that you can't totally 
guarantee privacy. 

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Re: [lubuntu-users] Support

2017-11-12 Thread Ralf Mardorf 
PS:

If RAM bars mounted to computer A should fail Memtest, do the same RAM
bars fail Memtest when mounted to computer B?

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Re: [lubuntu-users] Support

2017-11-12 Thread Ralf Mardorf 
On Sun, 12 Nov 2017 15:37:50 +, Ian Bruntlett wrote:
>Given personal experience of refurbishing computers for the Contact
>Computer Wombling/Refurbishing Project, I have found that when a
>computer I'm working on fails to run memtest86+ , that computer is not
>reliable enough for normal use. After a memtest86+ test has been
>passed, I wipe the hard drive using dban. If that fails, it is a
>strong indication that I'm going to have to change the hard drive.

I'm using Memtest myself as a point of reference to keep in mind, but
de facto RAM could be 100% ok after it failed and it could be borked
after it passed Memtest, let alone that one of the computers I tested
always failed when using Memtest from Ubuntu repositories and
always passed Memtest of the same version, when using a Memtest live
CD, both after shut down and disconnecting the PC from the mains.

There are tons of other possibilities that could cause issues, even
clearing CMOS _without_ replacing the battery could solve a lot of
issues.

Just running Memtest gains absolutely nothing. Running Memtest in
combination with other tests and actions is very helpful.

Smartctl is not perfect, but another link in the chain, even unplugging
SATA cables and connecting them again is important and so on and so
forth...

Just running one test, especially the free as in beer Memtest release
gains absolutely nothing, at least taking a look at /var/log,
journalctl and Co in combination with software testing hardware and
remounting, cleaning, etc. should be done. More experienced users could
use coolant spray etc. ...

Always keep in mind that measuring a faulty system by software running
on this system is fishy. A repair shop always tests equipment with
other equipment galvanically isolated from the mains.

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Re: [lubuntu-users] Support

2017-11-12 Thread Ian Bruntlett 
Hi Ralf et al,

On 12 November 2017 at 14:45, Ralf Mardorf 
wrote:

> Apart from this, it might have been a BIOS issue and maybe the RAM
> wasn't bad. Memtest is _not_ reliable. Using Memtest makes sense, but
> you shouldn't trust it.
>
> If RAM shouldn't pass Memtest you need to rule out other issues, at
> least you should replug the RAM bars.
>

Given personal experience of refurbishing computers for the Contact
Computer Wombling/Refurbishing Project, I have found that when a computer
I'm working on fails to run memtest86+ , that computer is not reliable
enough for normal use. After a memtest86+ test has been passed, I wipe the
hard drive using dban. If that fails, it is a strong indication that I'm
going to have to change the hard drive.

HTH,


Ian

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Re: [lubuntu-users] Support

2017-11-12 Thread Ralf Mardorf 
On Sun, 12 Nov 2017 07:27:39 -0700, Mark F wrote:
>It was so strange. I used Windows 95% of the time. It didn't freeze
>(even when installing it). But, for some reason Linux touched that bad
>memory in a way that caused my computer to hang.

Linux does use all available RAM, not only regarding Physical Address
Extension (PAE). 1. Windows might not have provided Physical Address
Extension (PAE). 2. Even if Windows should have had access to all
available RAM, it not necessarily does use all available RAM to cache
or as tmpfs or ... as Linux does.

Apart from this, it might have been a BIOS issue and maybe the RAM
wasn't bad. Memtest is _not_ reliable. Using Memtest makes sense, but
you shouldn't trust it.

If RAM shouldn't pass Memtest you need to rule out other issues, at
least you should replug the RAM bars.

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Re: [lubuntu-users] Support

2017-11-12 Thread Mark F 
On Sat, Nov 11, 2017 at 7:05 AM, Ian Bruntlett 
wrote:

>
> One thing to do is check for memory problems.
> ,,,
> * Use the down arrow key to select "Memory test (memtest86+)
>
...


That's *excellent* advice. About 20 years ago I would occasionally install
Linux. For a couple years I couldn't get it to install. It would freeze. I
thought it was a bad hard drive, or something about Linux had changed.
Someone mentioned "memtest" and sure enough, I had a bad memory stick.

It was so strange. I used Windows 95% of the time. It didn't freeze (even
when installing it). But, for some reason Linux touched that bad memory in
a way that caused my computer to hang. I would have never thought of memory
if someone hadn't mentioned it. (Even after experiencing it, I don't think
testing memory would come to mind very quickly.).

Mark
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