Raspberry Pi 4 Archives

NFS Root on Raspberry Pi 4

NFS, Raspberry Pi, Raspberry Pi 4 15 Responses »

Apr 122020

Picture of Raspberry Pi 4 box and Raspberry Pi 4 board below box

If you’re worried about destroying your SD Cards, need some more space, or just want to learn something new, I’m going to show you how to use an NFS root for the Raspberry Pi 4.

When you use an NFS Root with your Raspberry Pi, it stores the entire root filesystem on a remote NFS export (think of it as a network filesystem share). This means you’ll have as much space as the NFS export, and you’ll probably see way faster performance since it’ll be running at 1Gb/sec instead of the speed of the SD Card.

This also protects your SD card, as the majority of the reading and writing is performed on the physical storage of the NFS export, instead of the SD card in the Pi which has limited reads and writes.

What you’ll need

To get started, you’ll need:

Raspberry Pi 4
Ubuntu or Raspbian for Raspberry Pi 4 Image
A small SD card for the Boot Partition (1-2GB)
SD card for the Raspberry Pi Linux image
Access to another Linux system (workstation, or a Raspberry Pi)

There are multiple ways to do this, but I’m providing instructions on the easiest way it was for me to do this with the resources I had immediately available.

Instructions

To boot your Raspberry Pi 4 from an NFS root, multiple steps are involved. Below you’ll find the summary, and further down you’ll find the full instructions. You can click on an item below to go directly to the section.

The process:

Write the Linux image to an SD Card
Create boot SD Card for NFS Root
Prep the Linux install for NFS Root
Create the NFS Export
Copy the Linux install to the NFS Export
Copy and Modify the boot SD Card to use NFS Root
Boot using SD Card and test NFS Root

See below for the individual instructions for each step.

Write the Linux image to an SD Card

First, we need to write the SD Card Linux image to your SD card. You’ll need to know which device your SD card will appear to your computer. In my case it was /dev/sdb, make sure you verify the right device or you could damage your current Linux install.

Download Ubuntu or Raspbian for Raspberry Pi.
unzip or unxz depending on distribution to uncompress the image file.
Write the SD card image to SD card.
```
dd if=imagename.img of=/dev/sdb bs=4M
```

You now have an SD Card Linux install for your Raspberry Pi. We will later modify and then copy this to the NFS root and boot SD card.

Create boot SD Card for NFS Root

In this step, we’re going to create a bootable SD card that contains the Linux kernel and other needed files for the Raspberry Pi to boot.

This card will be installed in the Pi, load the kernel, and then kick off the boot process to load the NFS root.

I previously created a post to create a boot partition layout for a Raspberry Pi. Please follow those instructions to complete this step.

Later on in this guide, you’ll be copying the boot partition from the SD Card Linux image, on to this newly created boot SD Card for the NFS Root.

Prep the Linux install for NFS Root

There’s a few things we have to do to prep the Ubuntu or Raspbian Linux install to be usable as an NFS Root.

Boot the Raspbian or Ubuntu SD Card you create in the first step on your Raspberry Pi.
Complete the first boot procedures. Create your account, and complete the setup.
Enable and confirm SSH is working so you can troubleshoot.
Install the NFS client files using the following command:
```
apt install nfs-common
```
Open the /etc/network/interfaces file, and add the following line so that the Pi only get’s an IP once during boot:
```
iface eth0 inet manual
```
Modify your /etc/fstab entries to reflect the NFS root and the new boot SD card as per below.

For step 6, we need to modify the /etc/fstab entry for the root fs. It is different depending on whether you’re using Ubuntu or Raspbian.

For Raspbian, your /etc/fstab should look like this:

proc /proc proc defaults 0 0
LABEL=boot /boot vfat defaults 0 2
NFS-SERVER-IP:/nfs-export/PI-Raspbian / nfs defaults 0 0

For Ubuntu, your /etc/fstab should look like this:

LABEL=system-boot /boot/firmware vfat defaults 0 2
/dev/nfs / nfs defaults 0 0

After you do this, the Linux SD image may not boot again if directly installed in the Raspberry Pi, so make sure you’ve made the proper modifications before powering it down.

Create the NFS Export

In my case I used a Synology DS1813+ as an NFS server to host my Raspberry Pi NFS root images. But you can use any Linux server to host it.

If you’re using a synology disk station, create a shared folder, disable the recycling bin, leave everything else default. Head over to the “NFS Permissions” tab and create an ACL entry for your PI and workstations. You can also add a network segment for your entire network (ex. 192.168.0.0/24″) instead of specifying individual IPs.

Screenshot of Synology Create NFS rule for ACL — Create an NFS ACL Rule for Synology NFS Access

Once you create an entry, it’ll look like this. Note the “Mount path” in the lower part of the window.

Screenshot of NFS Shared Folder Permissions and Mount Point on Synology NAS — NFS Permissions and Mount Path for NFS Export

Now, if you’re using a standard Linux server the steps are different.

Install the require NFS packages:
```
apt install nfs-kernel-server
```
Create a directory, we’ll call it “nfs-export” on your root fs on the server:
```
mkdir /nfs-export/
```
Then create a directory for the Raspberry Pi NFS Root:
```
mkdir /nfs-export/PI-ImageName
```
Now edit your /etc/exports file and add this line to the file to export the path:
```
/nfs-export/PI-ImageName     IPorNetworkRange(rw,no_root_squash,async,insecure)
```
Reload the NFS exports to take affect:
```
exportfs -ra
```

Take note of the mount point and/or NFS export path, as this is the directory your Raspberry Pi will need to mount to access it’s NFS root. This is also the directory you will be copying your SD Card Linux install root FS to.

Copy the Linux install to the NFS Export

When you’re ready to copy your SD Card Linux install to your NFS Export, you’ll need to do the following. In my case I’ll be using an Ubuntu desktop computer to perform these steps.

When I insert the SD Card containing the Raspberry Pi Linux image, it appeared as /dev/sdb on my system. Please make sure you are using your proper device names to avoid using the wrong one to avoid writing or using the wrong disk.

Instructions to copy the root fs from the SD card to the NFS root export:

Mount the root partition of the SD Card Linux install to a directory. In my case I used directory called “old”.
```
mount /dev/sdb2 old/
```
Mount the NFS Export for the NFS Root to a directory. In my case I used a directory called “nfs”.
```
mount IPADDRESS:/nfs-export/PI-ImageName nfs/
```
Use the rsync command to transfer the SD card Linux install to the NFS Root Export.
```
rsync -avxHAXS --numeric-ids --info=progress2 --progress old/ nfs/
```
Unmount the directories.
```
umount old/
umount nfs/
```

Once this is complete, your OS root is now copied to the NFS root.

Copy and Modify the boot SD Card to use NFS Root

First we have to copy the boot partition from the SD Card Linux install to the boot SD card, then we need to modify the contents of the new boot SD card.

Top copy the boot files, follow these instructions.

Mount the boot partition of the SD Card Linux install to a directory. In my case I used directory called “old”.
```
mount /dev/sdb1 old/
```
Mount the new boot partition of the boot SD card to a new directory. In my case I used the directory called “new”.
```
mount /dev/sdc1 new/
```
Use the rsync command to transfer the SD card Linux install boot partition to the new boot SD card.
```
rsync -avxHAXS --numeric-ids --info=progress2 --progress old/ new/
```
Unmount the directories.
```
umount old/
umount new/
```

Now there are few steps we have to take to make to the boot SD card boot to an NFS Root.

We have to make a modification to the PI boot command. It is different depending on which Linux image (Ubuntu or Raspbian) you’re using.

First, insert the boot SD card, and mount it to a temporary directory.

mount /dev/sdc1 new/

If you’re running Ubuntu, your existing nobtcmd.txt should look like this:

dwc_otg.lpm_enable=0 console=tty1 root=/dev/mmcblk0p2 rootfstype=ext4 elevator=deadline rootwait

We’ll modify and replace some text to make it look like this. Don’t forget to change the command to reflect your IP and directory:

dwc_otg.lpm_enable=0 console=tty1 root=/dev/nfs nfsroot=IPADDRESS:/nfs-export/PI-Ubuntu,tcp,rw ip=dhcp rootfstype=nfs elevator=deadline rootwait

For Raspbian, your existing cmdline.txt should look like this:

console=serial0,115200 console=tty1 root=PARTUUID=97709164-02 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait

We’ll modify and replace some text to make it look like this. Don’t forget to change the command to reflect your IP and directory:

console=serial0,115200 console=tty1 root=/dev/nfs nfsroot=IPADDRESS:/nfs-export/PI-Raspbian,tcp rw vers=3 ip=dhcp rootfstype=nfs elevator=deadline rootwait

Once you make the modifications, save the file and unmount the SD card.

Your SD card is now ready to boot.

Boot using SD Card and test NFS Root

At this point, insert the boot SD Card in your Raspberry Pi and attempt to boot. All should be working now and it should boot and use the NFS root!

If you’re having issues, if the boot process stalls, or something doesn’t work right, look back and confirm you followed all the steps above properly.

You’re done!

You’re now complete and have a fully working NFS root for your Raspberry Pi. You’ll no longer worry about storage, have high speed access to it, and you’ll have some new skills!

And don’t forget to check out these Handy Tips, Tricks, and Commands for the Raspberry Pi 4!

Create Boot Partition Layout for a Raspberry Pi

Raspberry Pi, Raspberry Pi 4 2 Responses »

Mar 212020

During a previous project I needed to create a fresh and clean boot partition for a Raspberry Pi. I needed to create the partition layout required for the Raspberry Pi to see and boot a Linux kernel from.

There are many guides on the internet on how to write a Raspberry Pi image (which includes the system-boot partition), but I wanted a clean and fresh partition layout, without the additional partitions containing the Linux operating system.

I was creating a new Micro SD card with the purpose of using an NFS Root for the Raspberry Pi. For those of you that don’t know, you can boot a Raspberry Pi (or Linux computer) from local media, whether it’s a CD, USB Stick, Micro SD, or hard drive, and then have the actual operating system root file system be loaded via NFS. You can also use PXE to boot the kernel requiring no local storage, but that’s beyond the scope of this article.

Raspberry Pi default Partition layout

Below, we’ll look at the default partition layout you’d see on a Raspberry Pi using a prebuild linux image.

Disk /dev/sda: 59.6 GiB, 64021856256 bytes, 125042688 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x97709164
Device     Boot  Start       End   Sectors  Size Id Type
/dev/sda1         8192    532479    524288  256M  c W95 FAT32 (LBA)
/dev/sda2       532480 125042687 124510208 59.4G 83 Linux

I’m using a USB to Micro SD adapter to view the partitions on this card, so it’s being presented to the system as “/dev/sda”. On a normal computer “/dev/sda” is the first hard drive (usually the OS) so be careful when using these commands.

You’ll notice that “/dev/sda1” is the Raspberry Pi boot partition, with an Id of 3, and has the type of “W95 FAT32 (LBA)”.

The second partition which is the filesystem root (which I moved to NFS), is “/dev/sda2”, with an Id of 83, and has a type of “Linux”.

Creating a fresh partition layout with only the boot partition

In this guide we’re going to setup a Micro SD card with a fresh boot partition for the Raspberry Pi from scratch. We are not using an image and we are not using the expansion feature.

We’re going to assume that your destination SD card is empty. If it isn’t, you’ll need to delete all the partitions using “fdisk /dev/device”, and then deleted them with “d”.

Alternatively, to delete existing partition information you can wipe the MBR and partition table with the following command. Replace “/dev/device” with the actual device label for the card. Note that this will render existing data useless and unrecoverable.

dd if=/dev/zero of=/dev/DEVICE bs=512 count=1

Please Note: Make sure you are running this command on the right device. Afterwards, unplug and re-insert the SD card.

Creating the layout

On an empty Micro SD card:

Open fdisk on your card.
```
fdisk /dev/sda
```
Press “n” to create a partition.
Press “p” to make it a primary partition.
Press “1” to make it the first partition in the table.
Press <enter> to accept the default on start sector.
Type +size to choose the size. In my case I want 1GB, so I’ll type “+1G”.
After it’s created, press “a” to make it bootable.

Now we press “p” to print and view the partition table, as shown below.

Command (m for help): p
 Disk /dev/sda: 3.7 GiB, 3965190144 bytes, 7744512 sectors
 Geometry: 122 heads, 62 sectors/track, 1023 cylinders
 Units: sectors of 1 * 512 = 512 bytes
 Sector size (logical/physical): 512 bytes / 512 bytes
 I/O size (minimum/optimal): 512 bytes / 512 bytes
 Disklabel type: dos
 Disk identifier: 0x4eb27b84
 Device     Boot Start     End Sectors Size Id Type
 /dev/sda1  *     2048 2099199 2097152   1G 83 Linux

Now we need to set the partition type. Press “t” to set a partition type, choose the partition, and type “c” for “W95 FAT32 (LBA)”.
We’re now left with this partition table.
Press “w” to write and save, and exit fdisk.
We now need to format the partition. Run the following command on your device.
```
mkfs.vfat /dev/sda1
```

Finally, you can now set a label to the partition. Ubuntu uses the label “system-boot” whereas Raspbian uses “boot”. You can set it with the following command:

fatlabel /dev/device NEW_LABEL

You now have a clean partition layout that can be used to boot a Raspberry Pi. Remember that this is just the partition layout and the files are still needed from an image or your current running instance. These can simply be copied over.

In my case, I just mounted an old and the new partitions to directories and copied the data over. This allowed me to modify the new boot partition and ultimately make it boot in to an NFS root.

If you need just a simple boot partition, you don’t need to purchase large Micro SD cards.

Raspberry Pi 4 – Handy Tips, Tricks, and Commands

Linux, Raspberry Pi, Raspberry Pi 4 1 Response »

Mar 212020

CanaKit Raspberry Pi 4 case open with Fan Kit and running

In this post you’ll find a list of handy tips, tricks, and commands for your new Raspberry Pi 4.

I’ve been maintaining a document to record these so I can search and re-use them, and figured I’d share them on the blog for others to use as well.

I’m hoping to target both Raspbian and Ubuntu Server for the Raspberry Pi 4. If you have any feedback or input, please leave a comment!

Enable 64-Bit Kernel on Raspbian

Enables 64-bit kernel on Raspbian, however remember that the userspace is still 32-bit.

Run “rpi-update” to make sure you’re running latest firmware and kernel.
```
rpi-update
```
Add “arm_64bit=1” to “/boot/config.txt”
```
sudo echo arm_64bit=1 >> /boot/config.txt
```
Restart

Remove, comment out, or set the value to 0 to go back to a 32-bit kernel.

Get CPU Temperature on Raspbian

Run the command “sudo vcgencmd measure_temp” to get the CPU temperature on Raspbian.

pi@raspberrypi:~ $ sudo vcgencmd measure_temp
temp=38.0'C

Get CPU Temperature on Ubuntu Server

Run the command “paste <(cat /sys/class/thermal/thermal_zone/type) <(cat /sys/class/thermal/thermal_zone/temp) | column -s $’\t’ -t | sed ‘s/(.)..$/.\1°C/'” as root to get the CPU temperature on Ubuntu Server.

root@ubuntu:~# paste <(cat /sys/class/thermal/thermal_zone/type) <(cat /sys/class/thermal/thermal_zone/temp) | column -s $'\t' -t | sed 's/(.)..$/.\1°C/'
cpu-thermal  45.2°C

Add root CA (Certification Authority) certificates to the trust on Raspbian and Ubuntu Server

To add a root CA to your CA trust on your Linux instance, perform the following:

Save your certificate as a friendly-filename.crt (CRT extension is important) and copy to “/usr/local/share/ca-certificates/”.
Run the “update-ca-certificates” command as root or sudo.
```
update-ca-certificates
```

Install Cockpit Remote Web Administration

To install cockpit on your Raspberry Pi, run the following command as root or sudo:

apt install cockpit

After this, login to Cockpit on your Pi by pointring your browser to https://PI-IP-ADDRESS:9090

To install the Target CLI to configure the iSCSI Target

In order to configure the Linux kernel iSCSI target, you need the “targetcli” application/binary.

To install on Raspbian, run the command as root or sudo:

apt install targetcli

To install on Ubuntu Server, run the command as root or sudo:

apt install targetcli-fb

How to: Raspberry Pi 4 as an iSCSI SAN (iSCSI Target)

iSCSI, Raspberry Pi, Raspberry Pi 4 45 Responses »

Mar 182020

Raspberry Pi iSCSI Target with external USB drive attached

The Raspberry Pi 4 is a super neat little device that has a whole bunch of uses, and if there isn’t for something you’re looking for you can make one! As they come out with newer and newer generations of the Raspberry Pi, the hardware gets better, faster, and the capabilities greatly improve.

I decided it was time with the newer and powerful Raspberry Pi 4, to try and turn it in to an iSCSI SAN! Yes, you heard that right!

With the powerful quad core processor, mighty 4GB of RAM, and USB 3.0 ports, there’s no reason why this device couldn’t act as a SAN (in the literal sense). You could even use mdadm and configure it as a SAN that performs RAID across multiple drives.

Picture of a Raspberry Pi 4 with External USB 3 HD setup as an iSCSI Target and SAN — Raspberry Pi 4 with External USB 3 HD

In this article, I’m going to explain what, why, and how to (with full instructions) configure your Raspberry Pi 4 as an iSCSI SAN, an iSCSI Target.

Please Note: these instructions also apply to standard Linux PCs and Servers as well, but I’m putting emphasis that you can do this on SBCs like the Raspberry Pi.

A little history…

Over the years on the blog, I’ve written numerous posts pertaining to virtualization, iSCSI, storage, and other topics because of my work in IT. On the side as a hobby I’ve also done a lot of work with SBC (Single Board Computers) and storage.

Some of the most popular posts, while extremely old are:

Raspberry Pi as iSCSI Target (iSCSI Server) Proof of Concept – Overview – This was a proof of concept that discussed the idea, but didn’t provide instructions.
Fedora 17 ARM for Raspberry Pi – Compile your own kernel – This post was originally to compile a kernel to be used with the Lio-Target iSCSI target.
Lio-Target running on Soekris Net4801 – Proof of concept, instructions, and information on setting up the Soekris Net4801 as an iSCSI Target.

You’ll notice I put a lot of effort specifically in to “Lio-Target”…

When deploying or using Virtualization workloads and using shared iSCSI storage, the iSCSI Target must support something called SPC-3/SPC-4 Reservations.

SPC-3 and SPC-4 reservations allow a host to set a “SCSI reservation” and reserve the blocks on the storage it’s working with. By reserving the storage blocks, this allows numerous hosts to share the storage. Ultimately this is what allows you to have multiple hosts accessing the same volume. Please keep in mind both the iSCSI Target and the filesystem must support clustered filesystems and multiple hosts.

Originally, most of the open source iSCSI targets including the one that was built in to the Linux kernel did not support SCSI reservations. This resulted in volume and disk corruption when someone deployed a target and connected with multiple hosts.

Lio-Target specifically supported these reservations and this is why it had my focus. Deploying a Lio-target iSCSI target fully worked when using with VMware vSphere and VMware ESXi.

Ultimately, on January 15th, 2011 the iSCSI target in the Linux kernel 2.6.38 was replaced with Lio-target. All new Linux kernels use the Lio-Target as it’s iSCSI target.

What is an iSCSI Target?

An iSCSI target is a target that contains LUNs that you connect to with an iSCSI initiator.

The Target is the server, and the client is the initiator. Once connected to a target, you can directly access volumes and LUNs using iSCSI (SCSI over Internet).

What is it used for?

iSCSI is mostly used as shared storage for virtual environments like VMware vSphere (and VMware ESXi), as well as Hyper-V, and other hypervisors.

It can also be used for containers, file storage, remote access to drives, etc…

Why would I use or need this on the Raspberry Pi 4?

Some users are turning their Raspberry Pi’s in to NAS devices, whynot turn it in to a SAN?

With the powerful processor, 4GB of RAM, and USB 3.0 ports (for external storage), this is a perfect platform to act as a testbed or homelab for shared storage.

For virtual environments, if you wanted to learn about shared storage you could deploy the Raspberry Pi iSCSI target and connect to it with one or more ESXi hosts.

Or you could use this to remotely connect to a disk on a direct block level, although I’d highly recommend doing this over a VPN.

How do you connect to an iSCSI Target?

As mentioned above, you normally connect to an iSCSI Target and volume or LUN using an iSCSI initiator.

Using VMware ESXi, you’d most likely use the “iSCSI Software Adapter” under storage adapters. To use this you must first enable and configure it under the Host -> Configure -> Storage Adapters.

Image of the iSCSI Initiator software adapter configuration on VMware vSphere of an ESXi host. — VMware vSphere Host iSCSI Initiator Software Adapter

Using Windows 10, you could use the iSCSI initiator app. To use this simply search for “iSCSI Initiator” in your search bar, or open it from “Administrative Tools” under the “Control Panel”.

The Windows 10 iSCSI Initiator (iSCSI Properties) window. — Windows 10 iSCSI Initiator (iSCSI Properties)

There is also a Linux iSCSI initiator that you can use if you want to connect from a Linux host.

What’s needed to get started?

To get started using this guide, you’ll need the following:

Raspberry Pi 4
Ubuntu Server for Raspberry Pi or Raspbian
USB Storage (External HD, USB Stick, preferably USB 3.0 for speed)
A client device to connect (ESXi, Windows, or Linux)
Networking gear between the Raspberry Pi target and the device acting as the initiator

Using this guide, we’re assuming that you have already installed, are using, and have configured linux on the Raspberry Pi (setup accounts, and configured networking).

The Ubuntu Server image for Raspberry Pi comes ready to go out of the box as the kernel includes modules for the iSCSI Target pre-built. This is the easier way to set it up.

These instructions can also apply to Raspbian Linux for Raspberry Pi, however Raspbian doesn’t include the kernel modules pre-built for the iSCSI target and there are minor name differences in the apps. This is more complex and requires additional steps (including a custom kernel to be built).

Let’s get started, here’s the instructions…

If you’re running Raspbian, you need to compile a custom kernel and build the iSCSI Target Core Modules. Please follow my instructions (click here) to compile a custom kernel on Raspbian or Raspberry Pi. When you’re following my custom kernel build guide, in addition after running “make menuconfig”:

Navigate to “Device Drivers”.
Select (using space bar) “Generic Target Core Mod (TCM) and ConfigFS Infrastructure” so that it has an <M> (for module) next to it. Then press enter to open it. Example below.
```
<M> Generic Target Core Mod (TCM) and ConfigFS Infrastructure
```

Select all the options as <M> so that they compile as a kernel module, as shown below.

 --- Generic Target Core Mod (TCM) and ConfigFS Infrastructure
<M>   TCM/IBLOCK Subsystem Plugin for Linux/BLOCK
<M>   TCM/FILEIO Subsystem Plugin for Linux/VFS
<M>   TCM/pSCSI Subsystem Plugin for Linux/SCSI
<M>   TCM/USER Subsystem Plugin for Linux
<M>   TCM Virtual SAS target and Linux/SCSI LDD Fabcric loopback module
<M>   Linux-iSCSI.org iSCSI Target Mode Stack

Save the kernel config and continue following the “compile a custom raspberry pi kernel” guide steps.

If you’re running Ubuntu Server, the Linux kernel was already built with these modules so the action above is not needed.

We’re going to assume that the USB drive or USB stick you’ve installed is available on the system as “/dev/sda” for the purposes of this guide. Also please note that when using the create commands in the entries below, it will create it’s own unique identifiers on your system different from mine, please adjust your commands accordingly.

Let’s start configuring the Raspberry Pi iSCSI Target!

First we need to install the targetcli interface to configure the target.
As root (or use sudo) run the following command if you’re running Ubuntu Server.
```
apt install targetcli-fb
```
As root (or use sudo) run the following command if you’re running Raspbian.
```
apt install targetcli
```
As root (or using sudo) run “targetcli”.
```
targetcli
```
Create an iSCSI Target and Target Port Group (TPG).
```
cd iscsi/
create
```
Create a backstore (the physical storage attached to the Raspberry Pi).
```
cd /backstores/block
create block0 /dev/sda
```

Create an Access Control List (ACL) for security and access to the Target.

cd /iscsi/iqn.2003-01.org.linux-iscsi.ubuntu.aarch64:sn.eadcca96319d/tpg1/acls
create iqn.1991-05.com.microsoft:your.iscsi.initiator.iqn.com

Creating an ACL inside of targetcli for the iSCSI Target

Add, map, and assign the backstore (block storage) to the iSCSI Target LUN and ACL.

cd /iscsi/iqn.2003-01.org.linux-iscsi.ubuntu.aarch64:sn.eadcca96319d/tpg1/luns
create /backstores/block/block0

Mapping a backstore to LUN and ACL in TargetCLI

Review your configuration.
```
cd /
ls
```
Save your configuration and exit.
```
saveconfig
exit
```

That’s it, you can now connect to the iSCSI target via an iSCSI initiator on another machine.

For a quick example of how to connect, please see below.

Connect the ESXi Initiator

To connect to the new iSCSI Target on your Raspberry Pi, open up the configuration for your iSCSI Software Initiator on ESXi, go to the targets tab, and add a new iSCSI Target Server to your Dynamic Discovery list.

Add iSCSI Server to the Dynamic Discovery list on the iSCSI Software Initiator on ESXi — ESXi adding iSCSI Target Server (SAN) to iSCSI Software Initiator Dynamic Discovery

Once you do this, rescan your HBAs and the disk will now be available to your ESXi instance.

Connect the Windows iSCSI Initiator

To connect to the new iSCSI Target on Windows, open the iSCSI Initiator app, go to the “Discovery” tab, and click on the “Discover Portal” button.

Adding an iSCSI Target Server to the Windows iSCSI Software Initiator — Add iSCSI Target Server to Windows iSCSI Initiator

In the new window, add the IP address of the iSCSI Target (your Raspberry Pi), and hit ok, then apply.

Now on the “Targets” tab, you’ll see an entry for the discovered target. Select it, and hit “Connect”.

The targets list on Windows iSCSI Software Initiator — Windows iSCSI Initiator Targets List

You’re now connected! The disk will show up in “Disk Management” and you can now format it and use it!

Here’s what an active connection looks like.

The Microsoft iSCSI Initiator window open, showing an active connection to an iSCSI target, and iSCSI disk — Windows 10 iSCSI Initiator connect to iSCSI Target presenting a disk

That’s all folks!

Conslusion

There you have it, you now have a beautiful little Raspberry Pi 4 acting as a SAN and iSCSI Target providing LUNs and volumes to your network!

Picture of Raspberry Pi 4 iSCSI Target running Ubuntu Server with External USB 3 HD — Raspberry Pi 4 iSCSI Target with External USB 3 HD

Leave a comment and let me know how you made out or if you have any questions!

How to compile a Linux kernel for the Raspberry Pi 4 on Raspbian

Raspberry Pi, Raspberry Pi 4 23 Responses »

Mar 172020

So you’ve got a shiny new Raspberry Pi 4 and you need to compile a fresh and custom Linux kernel on Raspbian. You might need some features, some kernel modules, or you just want to compile the latest version from source.

I’m doing various projects (and blog posts) and with one of the projects, I found I needed to compile and enable a kernel module that wasn’t built in to the latest Raspbian image for the Pi 4.

This guide is also great if you just want to learn how to compile the kernel yourself!

Instructions

You may find that this guide is slightly different that the guide on the Raspberry Pi website and other sites. I like to append a unique name to the kernel version so I don’t have to touch the existing kernels. This allows me to revert or run multiple different custom kernels and switch back and forth.

Please note: You must be using a 32-bit kernel (or the default Raspbian kernel) to compile a new 32-bit kernel. You will not be able to compile a new kernel (32-bit or 64-bit) if you have booted in to the 64-bit kernel using the “arm_64bit=1” switch in “config.txt”. I’ve tried to compile a 64-bit kernel on Raspbian, but have not yet been able to do so. I’ll update with a new post once I figure it out.

And don’t forget, this can take some time and is CPU intensive. I installed a fan to help cool the temperatures while compilling!

This guide will compile a 32-bit kernel.

Install some packages required to building and compiling.

apt install raspberrypi-kernel-headers build-essential bc git wget bison flex libssl-dev make libncurses-dev

Create a directory for us to work in.
```
mkdir kernel
cd kernel
```

Clone the latest kernel sources using GIT.

git clone --depth=1 https://github.com/raspberrypi/linux

Setup the kernel configuration for compiling.

cd linux
KERNEL=kernel7l
make bcm2711_defconfig

Make any changes you want to the kernel configuration and append a friendly local version name by using make menuconfig.
```
make menuconfig
```
To change the friendly name, navigate to “General Setup” and select/modify “Local Version – append to kernel release”.
```
(-v7lstephen) Local version - append to kernel release
```
Compile the kernel, modules, and device tree blobs.
```
make -j4 zImage modules dtbs
```
Install compiled modules.
```
make modules_install
```

Copy the kernel, modules, and other files to the boot filesystem.

cp arch/arm/boot/dts/*.dtb /boot/
cp arch/arm/boot/dts/overlays/*.dtb* /boot/overlays/
cp arch/arm/boot/dts/overlays/README /boot/overlays/
cp arch/arm/boot/zImage /boot/kernel-stephen.img

Configure the PI to boot using the new kernel by modifying and adding the below line to “/boot/config.txt”.
```
kernel=kernel-stephen.img
```
Reboot!

Bam! You’re now using your shiny new Linux kernel on the Raspberry Pi 4!

To rescue a failed build or if the Pi won’t boot

If for some reason the Pi won’t boot, you can recover the previous kernel since we used a new name with the new kernel.

To rescue the image you’ll need another Linux computer that can read the Micro-SD card.

Insert the Micro-SD Card in the computer.
Mount the /boot/ filesystem on the Micro SD card to a local directory.
Edit the “config.txt” file and remove the “kernel=kernel-name.img” line we made above, or alternatively comment it out by inserting a “#” before the line.
```
#kernel=kernel-stephen.img
```
Save the file.
Unmount the partition.
Insert in the Raspberry Pi and boot!

You should now be back up and running and should be able to try again!

Leave some feedback and let me know if it worked for you. In the future I’ll be doing another post on compiling a 64-bit kernel for the Raspberry Pi 4 on Raspbian.

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