Delete a bond interface created from /etc/network/interfaces (ifupdown)?

Question

I made an attempt bonding two interfaces into one, created bond0, and found it unsatisfactory. I then reverted all changes made to /etc/network/interfaces and ran systemctl restart networking.service, but the bond interface still existed (shows up in ifconfig and ip link commands) and I had to run ip link set bond0 down or ifconfig bond0 down to force kick it out. How do I completely remove this interface without rebooting the server?

I'm on Debian Buster. The file was originally like this:

auto eno1
iface eno1 inet static
    # regular network settings like address, netmask, gateway etc.
auto eno2
iface eno2 inet static
    # regular network settings like address, netmask, gateway etc.

I turned both interfaces into one bond by changing it into this:

auto eno1
iface eno1 inet manual
    bond-master bond0
auto eno2
iface eno2 inet manual
    bond-master bond0

auto bond0
iface bond0 inet static
    # regular network settings like address, netmask, gateway etc.

score 3 · Accepted Answer · answered Dec 05 '19 at 17:32

The modern command to manage bond interfaces is, like for most other interfaces, ip link, here along with sysfs for the possible few things not handled directly through (rt)netlink. In this case:

ip link delete dev bond0

Any interface still enslaved when removing the bond will be detached, so there's no need to detach it first (using ip link set DEVICE nomaster).

An alternate sysfs method to do the same is:

echo -bond0 > /sys/class/net/bonding_masters

Ah, yes. This `iproute2` is what I'm using from day to day. – iBug Dec 05 '19 at 18:53 — iBug, Dec 05 '19 at 18:53

score 2 · Answer 2 · answered Dec 05 '19 at 16:38

bonding interfaces are managed by ifenslave(8) command line utility.

Below is an extract of the manpage:

NAME
     ifenslave -- Attach and detach slave network devices to a bonding device.

SYNOPSIS
     ifenslave [-acdfhuvV] [--all-interfaces] [--change-active] [--detach] [--force] [--help] [--usage] [--verbose] [--version] master slave ...

DESCRIPTION
     ifenslave is a tool to attach and detach slave network devices to a bonding device.  A bonding device will act like a normal Ethernet network device to the kernel,
     but will send out the packets via the slave devices using a simple round-robin scheduler.  This allows for simple load-balancing, identical to "channel bonding" or
     "trunking" techniques used in switches.

     The kernel must have support for bonding devices for ifenslave to be useful.

OPTIONS
     -a, --all-interfaces
             Show information about all interfaces.

     -c, --change-active
             Change active slave.

     -d, --detach
             Removes slave interfaces from the bonding device.

DISCLAIMER: i didn't tested the following

To totally remove bond0, i would:

ifconfig bond0 down
ifenslave -d bond0 eno1
ifenslave -d bond0 eno2
̀ rmmod bonding`

It should be enought.

Delete a bond interface created from /etc/network/interfaces (ifupdown)?

2 Answers2