Using HDD with Raspberry PI

[dimulec]

I tried to use some instructions to move root fs from the SD card to an external USB HDD. But nothing worked for me. So, I had to do id a bit differently. It probably would be better to post this to wiki. Except I have no idea how to do this. So, here are some (detailed) instructions on using USB HDD with RPI.

Warning: I used a very slow class 4 SD card since it is going to be used for only a boot partition
in the end. All operations with it take enormous amount of time. But I don't care as it will
not be used for actual work this RPI is intended for.



First 4 steps I did on my MAC. But any Linux computer could be used as well. Just replace diskutil
command with whatever Linux uses to unmount an fs.

1.

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diskutil unmount /Volumes/<whatever_name_your_SD_card_has>

My antivirus (ESET) sometimes blocks this operation. So, it has to be repeared 2-3 times.

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Volume boot on disk4s1 unmounted

Note: SD card reader on my MAC shows up as /dev/disk4. It could be different on your
computer. Check before overwriting it. "df" or "disk utility" could help with it.
On Linux use "df", "lsblk" or "blkid". I warned you!

2.

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dd if=/tmp/raspbian.img of=/dev/disk4 bs=1m conv=sync
   2144+0 records in
   2144+0 records out
   2248146944 bytes transferred in 917.897363 secs (2449236 bytes/sec)

3.

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touch /Volumes/boot/ssh

4.

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diskutil unmount /Volumes/boot

My antivirus (ESET) sometimes blocks this operation. So, it has to be repeared 2-3 times.

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Volume boot on disk4s1 unmounted

Next steps are performed on Raspberry PI. I used the latest RPI 4 B.



5. Boot RPI using this SD card. Use Ethernet cable, at least for now.

6. Find this RPI's IP and login (ssh) with pi/raspberry. You can find IP in your DHCP server's "current leases" list.

7. Don't forget to change password

8. Attach USB HDD. I use 4 TB external USB-3 HDD. Btw, it came with a regular USB-3 cable. So, I had to
get another one with additional USB power connector off Ebay. I connect it to a 60W power supply, which
also powers RPI. It has 6 USB sockets rtated 2.4 A each. So, I can probably connect another USB HDD
to it.

9. Look for USB HDD. In my case it is /dev/sda

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lsblk

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   NAME        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
   sda           8:0    0  3.7T  0 disk 
   └─sda1        8:1    0  3.7T  0 part 
   mmcblk0     179:0    0  3.7G  0 disk 
   ├─mmcblk0p1 179:1    0  256M  0 part /boot
   └─mmcblk0p2 179:2    0  3.4G  0 part /

9. Clear the HDD (make sure no useful data is there). You might skip this step and the following
one if you already have a partition that satisfies you. Like in the above case, I have an Linux
type partition that occupies the whole drive. But for the sake of this tutorial I will delete
and recreate it.

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dd if=/dev/zero of=/dev/sda bs=1M count=1000

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lsblk

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   NAME        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
   sda           8:0    0  3.7T  0 disk 
   mmcblk0     179:0    0  3.7G  0 disk 
   ├─mmcblk0p1 179:1    0  256M  0 part /boot
   └─mmcblk0p2 179:2    0  3.4G  0 part /

10. Create a big partition

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fdisk /dev/sda

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   Welcome to fdisk (util-linux 2.33.1).
   Changes will remain in memory only, until you decide to write them.
   Be careful before using the write command.

   Device does not contain a recognized partition table.
   The size of this disk is 3.7 TiB (4000787029504 bytes). DOS partition table format cannot be used on drives for volumes larger than 4294966784 bytes for 512-byte sectors. Use GUID partition table format (GPT).

   Created a new DOS disklabel with disk identifier 0x47d1a7f2.

   Command (m for help): g
   Created a new GPT disklabel (GUID: C9252DF5-BBE3-8D41-A6A1-146CB4C56AC0).

   Command (m for help): n
   Partition number (1-128, default 1): 
   First sector (2048-7814037133, default 2048): 
   Last sector, +/-sectors or +/-size{K,M,G,T,P} (2048-7814037133, default 7814037133): 

   Created a new partition 1 of type 'Linux filesystem' and of size 3.7 TiB.

   Command (m for help): w
   The partition table has been altered.
   Calling ioctl() to re-read partition table.
   Syncing disks.

11. Doublechecking

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lsblk

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   NAME        MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
   sda           8:0    0  3.7T  0 disk 
   └─sda1        8:1    0  3.7T  0 part 
   mmcblk0     179:0    0  3.7G  0 disk 
   ├─mmcblk0p1 179:1    0  256M  0 part /boot
   └─mmcblk0p2 179:2    0  3.4G  0 part /

12. Copy root fs to USB drive

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dd if=/dev/mmcblk0p2 of=/dev/sda1 bs=1M

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   3521+1 records in
   3521+1 records out
   3692560384 bytes (3.7 GB, 3.4 GiB) copied, 80.5194 s, 45.9 MB/s

13. Since we copied a live partition it needs to be cleaned.

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e2fsck -f /dev/sda1

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   e2fsck 1.44.5 (15-Dec-2018)
   rootfs: recovering journal
   Pass 1: Checking inodes, blocks, and sizes
   Pass 2: Checking directory structure
   Pass 3: Checking directory connectivity
   Pass 4: Checking reference counts
   Pass 5: Checking group summary information
   Free blocks count wrong (602687, counted=560037).
   Fix<y>? yes
   Free inodes count wrong (180977, counted=180594).
   Fix<y>? yes

   rootfs: ***** FILE SYSTEM WAS MODIFIED *****
   rootfs: 44750/225344 files (0.3% non-contiguous), 341467/901504 blocks

14. And expanded. It took 1 hour and 12 min to expand partition to full 4 TB.

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resize2fs /dev/sda1

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   resize2fs 1.44.5 (15-Dec-2018)
   Resizing the filesystem on /dev/sda1 to 976754385 (4k) blocks.
   The filesystem on /dev/sda1 is now 976754385 (4k) blocks long.

15. Mount new partition.

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mount /dev/sda1 /mnt

16. Get the PARTUUIDs for partitions.

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blkid

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   /dev/mmcblk0p1: LABEL_FATBOOT="boot" LABEL="boot" UUID="5203-DB74" TYPE="vfat" PARTUUID="6c586e13-01"
   /dev/mmcblk0p2: LABEL="rootfs" UUID="2ab3f8e1-7dc6-43f5-b0db-dd5759d51d4e" TYPE="ext4" PARTUUID="6c586e13-02"
   /dev/sda1: LABEL="rootfs" UUID="2ab3f8e1-7dc6-43f5-b0db-dd5759d51d4e" TYPE="ext4" PARTUUID="6debc4c1-0e9f-864e-ba94-ec95db099690"
   /dev/mmcblk0: PTUUID="6c586e13" PTTYPE="dos"

PARTUUID for the boot partition is 6c586e13-01
PARTUUID for the new root partition is 6debc4c1-0e9f-864e-ba94-ec95db099690

17. Edit /boot/cmdline.txt: replace PARTUUID, add a delay for USB HDD to become ready.

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nano /boot/cmdline.txt

New content:

console=serial0,115200 console=tty1 root=PARTUUID=6debc4c1-0e9f-864e-ba94-ec95db099690 rootdelay=5 rootfstype=ext4 elevator=deadline fsck.repair=yes rootwait

18. Edit /etc/fstab on the USB drive (/mnt/etc/fstab actually).

To make boot filesystem readonly add ",ro". Warning, after this you won't be able to install some updates
Replace PARTUUID for the root system too.

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   PARTUUID=6c586e13-01  /boot           vfat    defaults,ro       0       2
   PARTUUID=6debc4c1-0e9f-864e-ba94-ec95db099690  /               ext4    defaults,noatime  0       1

19. Reboot

After the reboot:

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df

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   Filesystem      1K-blocks    Used  Available Use% Mounted on
   [b]/dev/root      3846750000 1272876 3669881928   1% /[/b]
   devtmpfs           860916       0     860916   0% /dev
   tmpfs              993012       0     993012   0% /dev/shm
   tmpfs              993012   16804     976208   2% /run
   tmpfs                5120       4       5116   1% /run/lock
   tmpfs              993012       0     993012   0% /sys/fs/cgroup
   /dev/mmcblk0p1     258095   53933     204162  21% /boot
   tmpfs              198600       0     198600   0% /run/user/1000

20. Delete root partition from the SD card and backup the boot partition

20.1.

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fdisk /dev/mmcblk0

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   Welcome to fdisk (util-linux 2.33.1).
   Changes will remain in memory only, until you decide to write them.
   Be careful before using the write command.

   Command (m for help): d
   Partition number (1,2, default 2): 2

   Partition 2 has been deleted.

   Command (m for help): p
   Disk /dev/mmcblk0: 3.7 GiB, 3965190144 bytes, 7744512 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: 0x6c586e13

   Device         Boot Start    End Sectors  Size Id Type
   /dev/mmcblk0p1       8192 532479  524288  256M  c W95 FAT32 (LBA)

   Command (m for help): w
   The partition table has been altered.
   Syncing disks.

20.2. Not sure if this is the right way. But works for restoring the SD card.

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dd if=/dev/mmcblk0 of=/var/backups/boot_backup bs=1M count=260

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   260+0 records in
   260+0 records out
   272629760 bytes (273 MB, 260 MiB) copied, 5.96281 s, 45.7 MB/s

21. Install zoneminder or whatever you need that huge drive for.