unable to edit /proc/sys/net/ipv4/ip_forward in Xubuntu

Question

I try to change ip_forward from 0 to 1 but fail, even with root permission in Xubuntu 11.10. I don't have such similar problem while using Ubuntu 11.10

chiaki@chiaki:~$ sudo echo 1 > /proc/sys/net/ipv4/ip_forward 
bash: /proc/sys/net/ipv4/ip_forward: Permission denied

any idea?

Answer 1

You can not re-direct so easily with sudo. There are several potential solutions, including tee.

You can re-direct to files you own as the user calling sudo, such as files in your home directory, but not system files.

Example

# it works when re-direction to a location / file the user has permission to access
ubuntu@ubuntu:~$sudo echo "it works" > ~/file
ubuntu@ubuntu:~$cat file
it works

# But NOT if you do not have permission to access the target
ubuntu@ubuntu:~$sudo echo "it works" > /root/file
-bash: /root/file: Permission denied

Option one

use sudo bash -c and quote the entire command

sudo bash -c 'echo 1 > /proc/sys/net/ipv4/ip_forward'

Option two

Use tee

echo "1" | sudo tee /proc/sys/net/ipv4/ip_forward

Answer 2

If you want to change parameters in /proc/sys, the best thing to do is edit /etc/sysctl.conf and then run sysctl -p. That way your changes will persist across reboots.