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I typed apt-get update and then I saw a long list of

EDAC i7Core: Lost 127 memory errors

Please help me understand what has happened.

I am using ubuntu server edition 12.04 LTS

UPDATE:

I followed Gilles answer. I got the following when I do a dmesg

[113893.215234] EDAC MC0: CE error on CPU#0Channel#1_DIMM#0 (channel:1 slot:0 page:0x0 offset:0x0 grain:8 syndrome:0x0)
[113893.215237] EDAC MC0: CE error on CPU#0Channel#1_DIMM#0 (channel:1 slot:0 page:0x0 offset:0x0 grain:8 syndrome:0x0)
[113893.215240] EDAC MC0: CE error on CPU#0Channel#1_DIMM#0 (channel:1 slot:0 page:0x0 offset:0x0 grain:8 syndrome:0x0)
[113893.215243] EDAC MC0: CE error on CPU#0Channel#1_DIMM#0 (channel:1 slot:0 page:0x0 offset:0x0 grain:8 syndrome:0x0)
[113893.215246] EDAC MC0: CE error on CPU#0Channel#1_DIMM#0 (channel:1 slot:0 page:0x0 offset:0x0 grain:8 syndrome:0x0)
[113893.215248] EDAC MC0: CE error on CPU#0Channel#1_DIMM#0 (channel:1 slot:0 page:0x0 offset:0x0 grain:8 syndrome:0x0)
[113893.215251] EDAC MC0: CE error on CPU#0Channel#1_DIMM#0 (channel:1 slot:0 page:0x0 offset:0x0 grain:8 syndrome:0x0)
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1 Answer 1

up vote 4 down vote accepted

EDAC is the kernel component that watches for memory errors. You get a message about lost memory errors when so many errors occurred in a short interval that the kernel was unable to log them all.

A memory error is a bad thing. Check your kernel logs (/var/log/kern.log) for messages like this:

EDAC MC0: CE page 0x283, offset 0xce0, grain 8, syndrome 0x6ec3, row 0, channel 1 "DIMM_B1": amd76x_edac

CE indicates an error that was corrected. If your RAM has error correction, it's ok to have a corrected error now and then. But when you get to the point where memory errors get lost due to their number, it's high time to replace your RAM. The message indicates which RAM module (DIMM) is faulty.

If you see UE instead of CE, it means that an error was detected but not corrected. You may have corrupt data.

If your RAM and CPU don't support error correction, then the first sign you'll get that your RAM is defective is when you realize that your data is corrupted.

This is completely unrelated to apt-get update, that's just the command you happened to be executing when the errors happened.

Replace your RAM yesterday.

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Thanks Gilles nice Explanation. –  AgentCool Aug 19 '13 at 1:44
    
the kern.log is now 500Mb large. It is slow to open. From the first few lines, it appears to be CE errors. I was advised by people in the #ubuntu-server channel to do a memtest. What is the easiest way to do memtest? Googling shows I need a CD-rom or flash drive. I have never done it before. Advice? –  Kim Stacks Aug 19 '13 at 5:22
    
@kimsia You don't need a CD, Ubuntu installs memtest on your system. Make sure that your Grub menu can appear, then press and hold Shift while booting. When the Grub menu appears, select memtest. –  Gilles Aug 19 '13 at 7:32
    
I have never done this before, so I was hoping for a simple screen walkthrough. I googled youtube but most of them seem to be for windows. Does it apply to ubuntu server? youtube.com/results?search_query=memtest86+ubuntu –  Kim Stacks Aug 19 '13 at 13:16
2  
@kimsia Most CPUs aren't able to report memory corruption to the OS, hence usually you need to run memtest to diagnose potential memory corruption. Since your CPU has been able to report the errors to Linux, you don't need to run memtest. CE are corrected errors, but when you have that many corrected errors, there's a probability that some errors are going uncorrected. Replace the RAM module on channel 1 slot 0. –  Gilles Aug 20 '13 at 10:24
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