How to map ataX.0 identifiers in kern.log error messages to actual /dev/sdY devices?

Question

Consider following kern.log snippet:

 ata4.00: failed command: WRITE FPDMA QUEUED
 ata4.00: cmd 61/00:78:40:1e:6c/04:00:f0:00:00/40 tag 15 ncq 524288 out
        res 41/04:00:00:00:00/04:00:00:00:00/00 Emask 0x1 (device error)
 ata4.00: status: { DRDY ERR }
 ata4.00: error: { ABRT }
 ata4: hard resetting link
 ata4: nv: skipping hardreset on occupied port
 ata4: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
 ata4.00: configured for UDMA/133
 ata4: EH complete

How can I identify which hard drive the kernel actually means when it talks about ata4.00?

How can I find the corresponding /dev/sdY device name?

Answer 1

I puzzled a bit around what would be the enumeration scheme on my systems and I've came up with following algorithm:

The /dev/sdY devices are created in the same order as the ataX identifiers are enumerated in the kern.log while ignoring non-disk devices (ATAPI) and not-connected links.

Thus, following command displays the mapping:

$ grep '^May 28 2'  /var/log/kern.log.0  | \
   grep 'ata[0-9]\+.[0-9][0-9]: ATA-' | \
   sed 's/^.*\] ata//' | \
   sort -n | sed 's/:.*//' | \
   awk ' { a="ata" $1; printf("%10s is /dev/sd%c\n", a, 96+NR); }'
ata1.00 is /dev/sda
ata3.00 is /dev/sdb
ata5.00 is /dev/sdc
ata7.00 is /dev/sdd
ata8.00 is /dev/sde
ata10.00 is /dev/sdf

(Note that ata4 is not displayed because the above log messages are from another system.)

I am using /var/log/kern.log.0 and not /var/log/kern.log because the boot messages are already rotated. I grep for May 28 2 because this was the last boot time and I want to ignore previous messages.

To verify the mapping you can do some checks via looking at the output of:

$ grep '^May 28 2'  /var/log/kern.log.0  | \
grep 'ata[0-9]\+.[0-9][0-9]: ATA-'
May 28 20:43:26 hn kernel: [    1.260488] ata1.00: ATA-7: SAMSUNG SV0802N, max UDMA/100
May 28 20:43:26 hn kernel: [    1.676400] ata5.00: ATA-5: ST380021A, 3.19, max UDMA/10
[..]

And you can compare this output with hdparm output, e.g.:

$ hdparm -i /dev/sda

/dev/sda:

Model=SAMSUNG SV0802N [..]

(using Kernel 2.6.32-31)

I am still interested in alternative solutions, e.g. in a solution which does not need to access the kernel log (perhaps using some information from the /sys tree or something like that).

Answer 2

Here's my version, modified from above. Since I don't know the exact date the system was booted (for testing this it was 27 days ago), and I don't know which kern.log contains the data I need (some may be gzipped on my system), I use uptime and date to calculate an approximate system boot date (to the day, anyway), then use zgrep to search through all available kern.log files.

I also slightly modified the second grep statement, since it will now also show an ATAPI CD/DVD drive as well as ATA-* drives.

It could still use refinement (i.e. if system uptime is greater than a year), but should work OK for now.

#!/bin/bash

uptime=$(uptime | awk -F' '  '{ print $3" "$4 }' | sed s/,//)
date=$(date -d "$uptime ago" | awk '{print $2" "$3 }')
zgrep "$date"  /var/log/kern.log*  | \
grep 'ata[0-9]\+.[0-9][0-9]: ATA'  | \
sed 's/^.*\] ata//' | \
sort -n | sed 's/:.*//' | \
awk ' { a="ata" $1; printf("%10s is /dev/sd%c\n", a, 96+NR); }'