Unit file to load the `g_mass_storage` module after `iscsi.service`

g-mass-storage.service

# Adapted from: https://unix.stackexchange.com/a/260022/18065
[Unit]
Description=Loads kernel module for USB OTG
After=iscsi.service
DefaultDependencies=false

[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/sbin/modprobe g_mass_storage file=/dev/xyx
ExecStop=/sbin/rmmod g_mass_storage

[Install]
WantedBy=sysinit.target

sample-dmesg-output.txt

[   16.570113] Loading iSCSI transport class v2.0-870.
[   16.644803] iscsi: registered transport (tcp)
[   16.648670] scsi host0: iSCSI Initiator over TCP/IP
[   16.666917] scsi 0:0:0:0: Direct-Access       iSCSI Disk       0123 PQ: 0 ANSI: 7
[   16.668074] sd 0:0:0:0: Attached scsi generic sg0 type 0
[   16.668457] sd 0:0:0:0: Power-on or device reset occurred
[   16.680206] sd 0:0:0:0: [sda] 536870920 4096-byte logical blocks: (2.20 TB/2.00 TiB)
[   16.680242] sd 0:0:0:0: [sda] 32768-byte physical blocks
[   16.680594] sd 0:0:0:0: [sda] Write Protect is off
[   16.680618] sd 0:0:0:0: [sda] Mode Sense: 7f 00 10 08
[   16.681096] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, supports DPO and FUA
[   16.681974] sd 0:0:0:0: [sda] Optimal transfer size 1048576 bytes
[   16.721611]  sda: sda1
[   16.743345] sd 0:0:0:0: [sda] Attached SCSI disk
[   16.848690] Mass Storage Function, version: 2009/09/11
[   16.848727] LUN: removable file: (no medium)
[   16.849139] LUN: file: /dev/sda
[   16.849162] Number of LUNs=1
[   16.850087] g_mass_storage gadget: Mass Storage Gadget, version: 2009/09/11
[   16.850117] g_mass_storage gadget: userspace failed to provide iSerialNumber
[   16.850124] g_mass_storage gadget: g_mass_storage ready