How to manage linux bonding without ifenslave using sysfs


While working with a vyatta linux system I encountered a situation where bonded network interfaces were configured but the server didn’t have the ifenslave tool installed. As it turns out, linux bonded interfaces are easily managed directly through a simple sysfs interface. Here’s a quick run down of how to manage linux bonding without ifenslave using sysfs.

Create a new bond interface called bond0 using eth0 and eth1

#modprobe bond
 
echo "+bond0" >  /sys/class/net/bonding_masters
 
echo "+eth0" > /sys/class/net/bond0/bonding/slaves
echo "+eth1" > /sys/class/net/bond0/bonding/slaves

Remove a slave interface from bond0

echo "-eth0" > /sys/class/net/bond0/bonding/slaves

Delete a bond interface

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

Additional documentation

If you’re looking for more info here is the complete sysfs interface documentation from the linux kernel bonding driver

3.4 Configuring Bonding Manually via Sysfs
------------------------------------------
 
	Starting with version 3.0.0, Channel Bonding may be configured
via the sysfs interface.  This interface allows dynamic configuration
of all bonds in the system without unloading the module.  It also
allows for adding and removing bonds at runtime.  Ifenslave is no
longer required, though it is still supported.
 
	Use of the sysfs interface allows you to use multiple bonds
with different configurations without having to reload the module.
It also allows you to use multiple, differently configured bonds when
bonding is compiled into the kernel.
 
	You must have the sysfs filesystem mounted to configure
bonding this way.  The examples in this document assume that you
are using the standard mount point for sysfs, e.g. /sys.  If your
sysfs filesystem is mounted elsewhere, you will need to adjust the
example paths accordingly.
 
Creating and Destroying Bonds
-----------------------------
To add a new bond foo:
# echo +foo > /sys/class/net/bonding_masters
 
To remove an existing bond bar:
# echo -bar > /sys/class/net/bonding_masters
 
To show all existing bonds:
# cat /sys/class/net/bonding_masters
 
NOTE: due to 4K size limitation of sysfs files, this list may be
truncated if you have more than a few hundred bonds.  This is unlikely
to occur under normal operating conditions.
 
Adding and Removing Slaves
--------------------------
	Interfaces may be enslaved to a bond using the file
/sys/class/net/<bond>/bonding/slaves.  The semantics for this file
are the same as for the bonding_masters file.
 
To enslave interface eth0 to bond bond0:
# ifconfig bond0 up
# echo +eth0 > /sys/class/net/bond0/bonding/slaves
 
To free slave eth0 from bond bond0:
# echo -eth0 > /sys/class/net/bond0/bonding/slaves
 
	When an interface is enslaved to a bond, symlinks between the
two are created in the sysfs filesystem.  In this case, you would get
/sys/class/net/bond0/slave_eth0 pointing to /sys/class/net/eth0, and
/sys/class/net/eth0/master pointing to /sys/class/net/bond0.
 
	This means that you can tell quickly whether or not an
interface is enslaved by looking for the master symlink.  Thus:
# echo -eth0 > /sys/class/net/eth0/master/bonding/slaves
will free eth0 from whatever bond it is enslaved to, regardless of
the name of the bond interface.
 
Changing a Bond's Configuration
-------------------------------
	Each bond may be configured individually by manipulating the
files located in /sys/class/net/<bond name>/bonding
 
	The names of these files correspond directly with the command-
line parameters described elsewhere in this file, and, with the
exception of arp_ip_target, they accept the same values.  To see the
current setting, simply cat the appropriate file.
 
	A few examples will be given here; for specific usage
guidelines for each parameter, see the appropriate section in this
document.
 
To configure bond0 for balance-alb mode:
# ifconfig bond0 down
# echo 6 > /sys/class/net/bond0/bonding/mode
 - or -
# echo balance-alb > /sys/class/net/bond0/bonding/mode
	NOTE: The bond interface must be down before the mode can be
changed.
 
To enable MII monitoring on bond0 with a 1 second interval:
# echo 1000 > /sys/class/net/bond0/bonding/miimon
	NOTE: If ARP monitoring is enabled, it will disabled when MII
monitoring is enabled, and vice-versa.
 
To add ARP targets:
# echo +192.168.0.100 > /sys/class/net/bond0/bonding/arp_ip_target
# echo +192.168.0.101 > /sys/class/net/bond0/bonding/arp_ip_target
	NOTE:  up to 16 target addresses may be specified.
 
To remove an ARP target:
# echo -192.168.0.100 > /sys/class/net/bond0/bonding/arp_ip_target
 
To configure the interval between learning packet transmits:
# echo 12 > /sys/class/net/bond0/bonding/lp_interval
	NOTE: the lp_inteval is the number of seconds between instances where
the bonding driver sends learning packets to each slaves peer switch.  The
default interval is 1 second.
 
Example Configuration
---------------------
	We begin with the same example that is shown in section 3.3,
executed with sysfs, and without using ifenslave.
 
	To make a simple bond of two e100 devices (presumed to be eth0
and eth1), and have it persist across reboots, edit the appropriate
file (/etc/init.d/boot.local or /etc/rc.d/rc.local), and add the
following:
 
modprobe bonding
modprobe e100
echo balance-alb > /sys/class/net/bond0/bonding/mode
ifconfig bond0 192.168.1.1 netmask 255.255.255.0 up
echo 100 > /sys/class/net/bond0/bonding/miimon
echo +eth0 > /sys/class/net/bond0/bonding/slaves
echo +eth1 > /sys/class/net/bond0/bonding/slaves
 
	To add a second bond, with two e1000 interfaces in
active-backup mode, using ARP monitoring, add the following lines to
your init script:
 
modprobe e1000
echo +bond1 > /sys/class/net/bonding_masters
echo active-backup > /sys/class/net/bond1/bonding/mode
ifconfig bond1 192.168.2.1 netmask 255.255.255.0 up
echo +192.168.2.100 /sys/class/net/bond1/bonding/arp_ip_target
echo 2000 > /sys/class/net/bond1/bonding/arp_interval
echo +eth2 > /sys/class/net/bond1/bonding/slaves
echo +eth3 > /sys/class/net/bond1/bonding/slaves

https://www.kernel.org/doc/Documentation/networking/bonding.txt

One Response to “How to manage linux bonding without ifenslave using sysfs”

  1. Ray Says:

    Great article, thanks!

    cheers Ray

    [Reply]

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