Hello,
i'm using OMV for quite a while, but now I need some help with an upgrade problem.
I'm using my OMV 4.0 with Debian Stretch 9.1.
After upgrading to OMV 4.0 with omv-release-upgrade I get a serious error with my bonding device bond0.
The device was generated unter OMV3 with two slaves eth1 and eth2 and worked fine before upgrade.
After upgrading I decided to reorganize my network settings an tried to delete bond0.
Therefore I activated an other network card eth0 with the IP-Address of OMV, deleted bond0 and wrote the config.
I got the following error message:
ERROR: Failed to execute command 'export PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin; export LANG=C; echo '-bond0' > /sys/class/net/bonding_masters 2>&1' with exit code '2'
I wasn't able to write the configuration.
After that OMV is always trying to write this config. I tried several things to repair this error. There was no possibility within the WebUI.
At terminal I tried omv-firstaid to rewrite the network settings. The same error occured.
The file /sys/class/net/bonding_masters doesn't exist.
Recreating with
# modprobe -r bonding
# modprobe bonding
# echo '+bond0' > /sys/class/net/bonding_masters 2>&1
was successfull. Under /sys/class/net/ I can see
lrwxrwxrwx 1 root root 0 Nov 10 17:30 bond0 -> ../../devices/virtual/net/bond0
-rw-r--r-- 1 root root 4096 Nov 10 17:30 bonding_masters
lrwxrwxrwx 1 root root 0 Nov 9 18:29 eth0 -> ../../devices/pci0000:00/0000:00:15.3/0000:05:00.0/net/eth0
lrwxrwxrwx 1 root root 0 Nov 9 18:29 eth1 -> ../../devices/pci0000:00/0000:00:02.0/0000:01:00.0/net/eth1
lrwxrwxrwx 1 root root 0 Nov 9 18:29 eth2 -> ../../devices/pci0000:00/0000:00:02.0/0000:01:00.1/net/eth2
lrwxrwxrwx 1 root root 0 Nov 10 17:14 lo -> ../../devices/virtual/net/lo
Deactivating the device with root privileges and the upper shown command
# export PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin; export LANG=C; echo '-bond0' > /sys/class/net/bonding_masters 2>&1
is working.
bond0 is leaving
-rw-r--r-- 1 root root 4096 Nov 10 17:35 bonding_masters
lrwxrwxrwx 1 root root 0 Nov 10 17:30 eth0 -> ../../devices/pci0000:00/0000:00:15.3/0000:05:00.0/net/eth0
lrwxrwxrwx 1 root root 0 Nov 10 17:30 eth1 -> ../../devices/pci0000:00/0000:00:02.0/0000:01:00.0/net/eth1
lrwxrwxrwx 1 root root 0 Nov 10 17:30 eth2 -> ../../devices/pci0000:00/0000:00:02.0/0000:01:00.1/net/eth2
lrwxrwxrwx 1 root root 0 Nov 10 17:30 lo -> ../../devices/virtual/net/lo
So i reactivated the bond0 device and tried to write the config within the WebUI of OMV4.
I got the same error. 
ERROR: Failed to execute command 'export PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin; export LANG=C; echo '-bond0' > /sys/class/net/bonding_masters 2>&1' with exit code '2'
I tried the same again with chmodding the file bonding_masters
# chmod 777 /sys/class/net/bonding_masters
The same error as above.
So it seams that the configuration could not be written by Webui.
My last try was removing the bonding interface manually from
/etc/openmediavault/config.xml
I deleted the interface section for bond0 and restartet the Server.
After restart the bond0 was gone, but WebUI tried to execute the removing command again, with the same error
ERROR: Failed to execute command 'export PATH=/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin; export LANG=C; echo '-bond0' > /sys/class/net/bonding_masters 2>&1' with exit code '2' 
Any help for removing this error would be great.
Thanks for reading 