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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?

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possible duplicate of How to save power saving suggestions made by powertop –  enzotib Dec 26 '11 at 11:08
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2 Answers

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
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This completely worked for me! Just a couple of extra questions though: i) can I make those changes somehow persist through reboots and ii) why do those two commands even work?! and iii) why can't I even change the permission or the owner of that file, even when logged in as root? –  George Apr 15 at 21:11
    
@George - see askubuntu.com/questions/311053/… . As to your other questions, best ask a question rather then ask in the comments. Good luck to you. –  bodhi.zazen Apr 15 at 22:59
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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.

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