Monthly Archives: March 2020

CLI, Virtualization

JQ select specific value from array

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I had some AWS ec2 JSON output that I needed to parse. I wanted to grab a specific value from an array and it proved to be tricky for a JSON noob like me. I finally found this site which was very helpful: https://garthkerr.com/search-json-array-jq/. In my case I wanted the value of a specific AWS EC2 tag.

The trick is to grab down to the Tags[] array, and then pipe that to a select command. If your tags have dots in them (as mine did) then make sure to quote the tag name. Then add the .Value to the end of the select statement. This is my query:

jq -r '.Reservations[].Instances[].Tags[] | select (.Key == "EC2.Tag.Name").Value' jsonfile.json

The above query grabs all the tags (an array of Key,Value lines), then searches the result for a specific key “EC2.Tag.Name” and returns the Value line associated with it.

CLI, Hardware

WD*EZRZ NAS array spindown fix

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I recently acquired some 5TB Western Digital Blue drives (WD50EZRZ.) These particular drives were shucked from external USB enclosures. When I tried to add them into my ZFS raid array, though, I ran into constant problems. I would continually get errors like this from the kernel:

[155069.298001] sd 0:0:10:0: attempting task abort! scmd(ffff8f0678887100)
[155069.298005] sd 0:0:10:0: [sdk] tag#5 CDB: Write(16) 8a 00 00 00 00 01 a8 1e 77 10 00 00 00 58 00 00
[155069.298008] scsi target0:0:10: handle(0x0014), sas_address(0x5001438023a93296), phy(22)
[155069.298010] scsi target0:0:10: enclosure logical id(0x5001438023a932a5), slot(53) 
[155069.298012] sd 0:0:10:0: task abort: SUCCESS scmd(ffff8f0678887100)
[155069.298016] sd 0:0:10:0: [sdk] tag#5 FAILED Result: hostbyte=DID_TIME_OUT driverbyte=DRIVER_OK
[155069.298018] sd 0:0:10:0: [sdk] tag#5 CDB: Write(16) 8a 00 00 00 00 01 a8 1e 77 10 00 00 00 58 00 00
[155069.298020] blk_update_request: I/O error, dev sdk, sector 7115536144
[155069.298023] zio pool=storage vdev=/dev/disk/by-id/ata-WDC_WD50EZRZ-32RWYB1_WD-WX31XXXXXVA-part1 error=5 type=2 offset=3643153457152 size=45056 flags=180880

After a couple of said errors, the drive would be marked as bad and taken out of the array. A battery of tests on a different system revealed the drives to be fine. It did not matter where I inserted these drives on my NAS, they did the same thing, even on ports I knew had working drives. It wasn’t a cabling or other hardware issue.

The drives would resilver back into the array just fine, and then pop out again at random intervals – sometimes minutes later, other times hours later. After a lot of research I came across this post that got me thinking – this sounds like a drive spindown issue! The random nature of it could simply be the drives not being used and then powering themselves down.

I tried using hdparm to set the spindown timer but was greeted with this lovely error:

sudo hdparm -B /dev/sdk
/dev/sdk:
 APM_level	= not supported

I eventually found this post complaining about their Western Digital drives spinning down aggressively.

idle3 to the rescue

The above post mentions apmtimer which did not help me, however more searches reveled this godsend: idle3-tools

idle3-tools is an open source utility to handle spindown on Western Digital drives themselves (not the OS level.)

Download & compile idle3:

wget https://sourceforge.net/projects/idle3-tools/files/latest/download
cd idle3-tools-0.9.1/
make
sudo make install

Use idle3 to query current spindown status (update drive letters to suit your needs)

for drive in {a..p}; do echo /dev/sd$drive; sudo idle3ctl -g /dev/sd$drive; done

For anything that doesn’t say Idle3 timer is disabled run the following:

sudo idle3ctl -s 0 /dev/sd(DRIVE_LETTER)

No more drive spindown!

CLI, Networking, OS

proxmox openvswitch bond

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Recently I had to switch my Proxmox server which was using Linux bonds to using openvswitch. These are my notes:

Install openvswitch:

apt install openvswitch-switch

Configure openvswitch to bond interfaces and use VLANs using https://pve.proxmox.com/wiki/Open_vSwitch as an example:

allow-vmbr0 bond0
iface bond0 inet manual
	ovs_bonds enp4s0f0 eno1
	ovs_type OVSBond
	ovs_bridge vmbr0
	ovs_options bond_mode=active-backup

auto lo
iface lo inet loopback

iface eno1 inet manual

iface enp4s0f0 inet manual

allow-ovs vmbr0
iface vmbr0 inet manual
	ovs_type OVSBridge
	ovs_ports bond0 vlan50 vlan10

#Proxmox communication
allow-vmbr0 vlan50
iface vlan50 inet static
  ovs_type OVSIntPort
  ovs_bridge vmbr0
  ovs_options tag=50
  ovs_extra set interface ${IFACE} external-ids:iface-id=$(hostname -s)-${IFACE}-vif
  address 10.0.50.2
  netmask 255.255.255.0
  gateway 10.0.50.1

#Storage network
allow-vmbr0 vlan10
iface vlan10 inet static
  ovs_type OVSIntPort
  ovs_bridge vmbr0
  ovs_options tag=10
  ovs_extra set interface ${IFACE} external-ids:iface-id=$(hostname -s)-${IFACE}-vif
  address 192.168.10.2
  netmask 255.255.255.0

List active interface:

OPENVSWITCH – Playing with Bonding on Openvswitch

ovs-appctl bond/show bond0

Update 3/14/2020

I realized that openvswitch won’t fail back over to the original slave once it comes back online. I couldn’t for the life of me find the equivalent of bond-primary syntax for openvswitch; however I did find this command:

ovs-appctl list-commands

which reveals this command:

bond/set-active-slave port slave

So you can manually fallback using this command:

ovs-appctl bond/set-active-slave bond0 enp4s0f1

CLI, OS

chroot into encrypted drive

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I foolishly went browsing in my EFI partition on my Ubuntu (Elementary OS) laptop and decided to delete the Ubuntu folder. This made my laptop unbootable. This was my procedure to bring it back to life:

Boot into Ubuntu Live CD / USB environment

Decrypt LUKS encrypted drive (https://blog.sleeplessbeastie.eu/2015/11/16/how-to-mount-encrypted-lvm-logical-volume/)

sudo fdisk -l
#Determine encrypted partition is /dev/nvme0n1p3 because it's the largest
sudo cryptsetup luksOpen /dev/nvme0n1p3 encrypted_device
sudo vgchange -ay

Mount encrypted drive & chroot (https://askubuntu.com/questions/831216/how-can-i-reinstall-grub-to-the-efi-partition)

sudo mount /dev/elementary-vg/root /mnt
sudo mount /dev/nvme0n1p2 /mnt/boot/
sudo mount /dev/nvme0n1p1 /mnt/boot/efi
for i in /dev /dev/pts /proc /sys /run; do sudo mount -B $i /mnt$i; done
sudo chroot /mnt
sudo grub-install
update-grub  

#end chroot & unmount
exit
cd
for i in /mnt/dev/pts /mnt/dev  /mnt/proc /mnt/sys /mnt/run /mnt/boot/efi /mnt/boot /mnt; do sudo umount $i;  done