mkfs.vfat: unable to open {partition}: No such file or directory (command succeeds, but throws this error and blocks rest of script)

Question

Update: I got this working but am still not 100% sure why. I've appended the fully and consistently working script to the end for reference.

I'm trying to script a series of disk partition commands using sgdisk and mkfs.vfat. I'm working from a Live USB (NixOS 21pre), have a blank 1TB M.2 SSD, and am creating a 1GB EFI boot partition, and a 999GB ZFS partition.

Everything works up until I try to create a FAT32 filesystem on the EFI partition, using mkfs.vfat, where I get the error in the title.

However, the odd thing is, the mkfs.vfat command succeeds, but throws that error anyway and blocks the rest of the script. Any idea why it's doing this and how to fix it?

Starting with an unformatted 1TB M.2 SSD:

$  sudo parted /dev/disk/by-id/wwn-0x5001b448b94488f8 print
Error: /dev/sda: unrecognised disk label
Model: ATA WDC WDS100T2B0B- (scsi)                                        
Disk /dev/sda: 1000GB
Sector size (logical/physical): 512B/512B
Partition Table: unknown
Disk Flags: 

Script:

$ ls
total 4
drwxr-xr-x  2 nixos users   60 May 18 20:25 .
drwx------ 17 nixos users  360 May 18 15:24 ..
-rwxr-xr-x  1 nixos users 2225 May 18 19:59 partition.sh

$  cat partition.sh
#!/usr/bin/env bash
#make gpt partition table and boot & rpool partitions for ZFS on 1TB M.2 SSD

#error handling on
set -e

#wipe the disk with -Z, then create two partitions, a 1GB (945GiB) EFI boot partition, and a ZFS root partition consisting of the rest of the drive, then print the results
DISK=/dev/disk/by-id/wwn-0x5001b448b94488f8
sgdisk -Z $DISK
sgdisk -n 1:0:+954M -t 1:EF00 -c 1:efi $DISK
sgdisk -n 2:0:0 -t 2:BF01 -c 2:zroot $DISK
sgdisk -p /dev/sda

#make a FAT32 filesystem on the EFI partition, then mount it
#mkfs.vfat -F 32 ${DISK}-part1 (troubleshooting with hardcoded version below)
mkfs.vfat -F 32 /dev/disk/by-id/wwn-0x5001b448b94488f8-part1
mkdir -p /mnt/boot
mount ${DISK}-part1 /mnt/boot

Result (everything fine until mkfs.vfat, which throws error and blocks the rest of the script):

$  sudo sh partition.sh
GPT data structures destroyed! You may now partition the disk using fdisk or
other utilities.
Creating new GPT entries in memory.
Setting name!
partNum is 0
The operation has completed successfully.
Setting name!
partNum is 1
The operation has completed successfully.
Disk /dev/sda: 1953525168 sectors, 931.5 GiB
Model: WDC WDS100T2B0B-
Sector size (logical/physical): 512/512 bytes
Disk identifier (GUID): 77ED6A41-E722-4FFB-92EC-975A37DBCB97
Partition table holds up to 128 entries
Main partition table begins at sector 2 and ends at sector 33
First usable sector is 34, last usable sector is 1953525134
Partitions will be aligned on 2048-sector boundaries
Total free space is 2014 sectors (1007.0 KiB)

Number  Start (sector)    End (sector)  Size       Code  Name
   1            2048         1955839   954.0 MiB   EF00  efi
   2         1955840      1953525134   930.6 GiB   BF01  zroot
mkfs.fat 4.1 (2017-01-24)
mkfs.vfat: unable to open /dev/disk/by-id/wwn-0x5001b448b94488f8-part1: No such file or directory

Verifying the partitioning and FAT32 creation commands worked:

$ sudo parted /dev/disk/by-id/wwn-0x5001b448b94488f8 print
Model: ATA WDC WDS100T2B0B- (scsi)
Disk /dev/sda: 1000GB
Sector size (logical/physical): 512B/512B
Partition Table: gpt
Disk Flags: 

Number  Start   End     Size    File system  Name   Flags
 1      1049kB  1001MB  1000MB  fat32        efi    boot, esp
 2      1001MB  1000GB  999GB                zroot

Fwiw, the same command works on the commandline with no error:

$  sudo mkfs.vfat -F 32 /dev/disk/by-id/wwn-0x5001b448b94488f8-part1
mkfs.fat 4.1 (2017-01-24)

Success. But why no error on the commandline, but an error in the script?

Update: fully and consistently working script:

#!/usr/bin/env bash
#make UEFI (GPT) partition table and two partitions (FAT32 boot and ZFS rpool) on 1TB M.2 SSD

#error handling on
set -e

#vars
DISK=/dev/disk/by-id/wwn-0x5001b448b94488f8
POOL='rpool'

#0. if /mnt/boot is mounted, umount it; if any NixOS filesystems are mounted, unmount them
if mount -l | grep -q '/mnt/boot'; then
  umount -f /mnt/boot
fi
if mount -l | grep -q '/mnt/nix'; then
  umount -fR /mnt
fi

#1. if a zfs pool exists, delete it
if zpool list | grep -q $POOL; then
  zfs unmount -a
  zpool export $POOL
  zpool destroy -f $POOL
fi

#2. wipe the disk
sgdisk -Z $DISK
wipefs -a $DISK

#3. create two partitions, a 1GB (945GiB) EFI boot partition, and a ZFS root partition consisting of the rest of the drive, then print the results
sgdisk -n 1:0:+954M -t 1:EF00 -c 1:efiboot $DISK
sgdisk -n 2:0:0 -t 2:BF01 -c 2:zfsroot $DISK
sgdisk -p /dev/sda

#4. notify the OS of partition updates, and print partition info
partprobe
parted ${DISK} print

#5. make a FAT32 filesystem on the EFI boot partition
mkfs.vfat -F 32 ${DISK}-part1

#6. notify the OS of partition updates, and print new partition info
partprobe
parted ${DISK} print

#mount the partitions in nixos-zfs-pool-dataset-create.sh script. Make sure to first mount the ZFS root dataset on /mnt before mounting and subdirectories of /mnt.

Answer 1

It may take time for kernel to be notified about partition changes. Try calling partprobe before mkfs, to request kernel to re-read the partition tables.