lhsw is terrible for detecting disks

[Rob Thomas]

Various bugs report that lshw isn't reporting disks, or disk sizes correctly. This is because lshw, while venerable, is somewhat out of date with modern hardware.

I suggest avoiding that totally, and replacing 100% of the disk detection code with this one liner:

 parted -lms | awk 'found{ if(!/dev\/mapper/){print};found=0} /^BYT;$/{found=1}'

This will reliably and repeatably output a single line per available disk, with a valid size:

root@t0:~/maas# parted -lms | awk 'found{ if(!/dev\/mapper/){print};found=0} /^BYT;$/{found=1}'
/dev/cciss/c0d0:147GB:cpqarray:512:512:msdos:Compaq Smart Array:;
root@t0:~/maas#

root@bay6:/var/log# parted -lms | awk 'found{ if(!/dev\/mapper/){print};found=0} /^BYT;$/{found=1}'
/dev/cciss/c0d0:147GB:cpqarray:512:512:msdos:Compaq Smart Array;
/dev/cciss/c0d1:147GB:cpqarray:512:512:gpt:Compaq Smart Array;
root@bay6:/var/log#

root@gw:~# parted -lms | awk 'found{ if(!/dev\/mapper/){print};found=0} /^BYT;$/{found=1}'
/dev/sda:42.9GB:scsi:512:512:msdos:VMware Virtual disk;
root@gw:~#

It also explicitly excludes LVM (the /dev/mapper negation) volumes.

This provides output in an easy to parse format, and will never be out of date, unlike lshw.

[Blake Rouse (blake-rouse)]

I have to agree with you that lshw is not the best source. As I am currently trying to detect that disks are SSD, and lshw does not provide that information.

I am looking into replacing lshw with another method of detecting disks, for the new storage work for MAAS. I will take into account your suggestion here.

Thanks,
Blake

[Rob Thomas (xrobau)]

Well, that's slightly harder to do in an awk one liner.

Still doable, but not readable.

cat /sys/block/cciss\!c0d0/queue/rotational
1

root@t0:~# cat /sys/block/cciss\!c0d0/queue/rotational
1
root@t0:~# echo /dev/sda | sed 's/\//!/g; s/!dev!//'
sda
root@t0:~# echo /dev/cciss/c0d0 | sed 's/\//!/g; s/!dev!//'
cciss!c0d0
root@t0:~#

If it's 1 it's spinning, if it's zero it's not.

[Rob Thomas (xrobau)]

As that was a bit of an interesting puzzle:

#!/bin/bash

# Basic HDD detection script.
# Written by Rob Thomas, <email address hidden>
# Code available under the licence of your choice.

ALLDISKS=$(parted -lms | awk 'found{ if(!/dev\/mapper/){print};found=0} /^BYT;$/{found=1}')

while read -r l; do
        RAWDISK=`echo "$l" | cut -d: -f1 | sed -r 's/\//!/g; s/!dev!//'`
        SSD="?"
        if [ -e "/sys/block/$RAWDISK/queue/rotational" ]; then
                SSD=`cat /sys/block/$RAWDISK/queue/rotational`
        fi
        echo $l$SSD
done <<< "$ALLDISKS"

That will append ? (if there's an error), 0 or 1 to the end of the string