Can't write to file owned by root

[O2Blevel]

I'm trying to edit a file owned by root using this:


sudo -i
echo powersave > /sys/module/pcie_aspm/parameters/policy
exit

I think that gets around the redirecting sudo problem but I still can't edit the file.

I'd appreciate any help.

[timswait]

Use sudo to open whatever notepad editor you use (for example I use kate in kubuntu, it might be gedit in ubuntu). So from terminal just type "sudo kate", "sudo gedit", etc and it'll open your notepad editor with root access. You can then open the file you want to edit, edit and save it.

[drmrgd]

If you're going to run graphically, you should use gksudo (or kdesudo for Kubuntu), and not sudo. See this (scroll down to the "Graphical sudo" section):

https://help.ubuntu.com/community/RootSudo

[O2Blevel]

Thanks for the quick replies, but when I tried gksu gedit, it would not let me save the changes. It says I don't have the permissions necessary to save the file.

[steeldriver]

I don't see why 'sudo -i' wouldn't work (unless the file mode is readonly for root? by default it should be rw I think)


$ ls -l /sys/module/pcie_aspm/parameters/policy
-rw-r--r-- 1 root root 4096 Jun 25 09:04 /sys/module/pcie_aspm/parameters/policy


However I've worked around the redirect issue in the past using 'sudo tee'


echo powersave | sudo tee /sys/module/pcie_aspm/parameters/policyIf you don't want to see the echoed output you can redirect *that* to /dev/null


echo powersave | sudo tee /sys/module/pcie_aspm/parameters/policy 1>/dev/nullBTW those sys files are kind of funny - you don't really edit them literally - when you write a new powersave policy (e.g. 'powersave' or 'default') they kind of rearrange themselves i.e.:



$ cat /sys/module/pcie_aspm/parameters/policy
[default] performance powersave
$
$ echo powersave | sudo tee /sys/module/pcie_aspm/parameters/policy 1>/dev/null
$
$ cat /sys/module/pcie_aspm/parameters/policy
default performance [powersave]
$
$ echo default | sudo tee /sys/module/pcie_aspm/parameters/policy 1>/dev/null
$
$ cat /sys/module/pcie_aspm/parameters/policy
[default] performance powersave
$

[O2Blevel]

When I do this command:


echo powersave | sudo tee /sys/module/pcie_aspm/parameters/policy 1>/dev/null

I get this result:


tee: /sys/module/pcie_aspm/parameters/policy: Operation not permitted

[steeldriver]

... and did you check the permissions?


ls -l /sys/module/pcie_aspm/parameters/policy

[O2Blevel]

Yes, the permissions are the same as yours.

I just tried running the command from the recovery console and got the same response, tee operation not permitted.

[steeldriver]

EDIT: OK I think I can confirm what's happening - notice your error is now "operation not permitted" rather than "permission denied"?

That's likely because ASPM is disabled at the BIOS level - in fact I tested it on a different machine and got the same behavior as you - until I updated grub with 'pcie_aspm=force' and now it *does* work

I don't know if forcing pcie_aspm is bad for other reasons though - ymmv

[philinux]

In the past I've edited this file.

/etc/init.d/ondemand

But it's easier to use indicator-cpufreq to change on the fly. (Unity 12.04)

[steeldriver]

nevermind - edited my earlier post instead

[VanillaMozilla]

You misused the sudo command.

The command is something like this:
sudo [switches] <command>

not
sudo [switches]
<command>

If you were using gedit (or another gui program), the command would be something like
gksudo gedit [filename]
or
gksudo gedit [filename] &

I would not recommend using su or gksu.

[CharlesA]

gksu is a link to gksudo. su is not a link to sudo, however.

[O2Blevel]

EDIT: OK I think I can confirm what's happening - notice your error is now "operation not permitted" rather than "permission denied"?

That's likely because ASPM is disabled at the BIOS level - in fact I tested it on a different machine and got the same behavior as you - until I updated grub with 'pcie_aspm=force' and now it *does* work

I don't know if forcing pcie_aspm is bad for other reasons though - ymmv

Looks like I'm going to have to edit grub. I wanted to edit the policy file to see how it worked and whether it caused any problems before I made it permanent, but I don't see any other way.

Thanks for your help.

[steeldriver]

you can always add it one-time (press 'shift' to get the grub boot screen if you usually boot straight in - then 'e' to edit the boot line) rather than editing/updating the grub config - that way if it fails you can just reboot as before

[VanillaMozilla]

You misused the sudo command.
Oops, probably not, due to fancy use of the -i switch. And gksu didn't work either, so I guess the problem is not the sudo command. My mistake.

[CharlesA]

gksu is a link to gksudo. su is not a link to sudo, however.

It's the other way around for gksudo:


charles@Precise:~$ ls -l $(which gksu)
-rwxr-xr-x 1 root root 28128 Nov 9 2011 /usr/bin/gksu
charles@Precise:~$ ls -l $(which gksudo)
lrwxrwxrwx 1 root root 4 May 24 11:50 /usr/bin/gksudo -> gksu

[Rebelli0us]

Isn't that an awful lot of work just for editing your file on your computer?

[CharlesA]

Isn't that an awful lot of work just for editing your file on your computer?
I suppose so.

It would be easier just to open the file in gedit or nano or something and add powersave at the bottom instead of messing with redirects:


gksu gedit /sys/module/pcie_aspm/parameters/policy

[O2Blevel]

Isn't that an awful lot of work just for editing your file on your computer?

That's what my problem is, I can't edit the file. Don't know why.

[CharlesA]

That's what my problem is, I can't edit the file. Don't know why.

Not even with nano?


sudo nano /sys/module/pcie_aspm/parameters/policy

I just tested it on my 12.04 box and I was able to change read it, but not change it.

Have you run a fsck lately?


sudo touch /forcefsck

Reboot.

[sandyd]

Probably
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=663202

[steeldriver]

That's what my problem is, I can't edit the file. Don't know why.

um... didn't we figure out that the problem is not that you can't edit the file, it's that the operation implied by changing the file (i.e. changing the pcie power management policy) is not permitted by BIOS?

[sandyd]

um... didn't we figure out that the problem is not that you can't edit the file, it's that the operation implied by changing the file (i.e. changing the pcie power management policy) is not permitted by BIOS?
Check the bug above.
"And indeed the parameter is no longer setable with kernel 3.2.9:"

The other bug that references this is burried somewhere.

[O2Blevel]

um... didn't we figure out that the problem is not that you can't edit the file, it's that the operation implied by changing the file (i.e. changing the pcie power management policy) is not permitted by BIOS?

I've checked my BIOS a couple of times and I don't see anything there that would be a problem. Everything is set to the default values. It's a Dell laptop, E1505.

[sandyd]

Bug reported.
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1017746

[sandyd]

I've checked my BIOS a couple of times and I don't see anything there that would be a problem. Everything is set to the default values. It's a Dell laptop, E1505.
Please run

apport-cli -f -p linux-image-`uname -r`--save bug.apport
and attach the bug.apport file in your home folder.

[philinux]

Please run


apport-collect 1017746
You will need a launchpad account to send the information to the bug.

Only the original bug reporter can run that I think. I've had this error in the past even though I'm subscribed to a bug.

Worth a shot though as the system might have changed.

[sandyd]

Only the original bug reporter can run that I think. I've had this error in the past even though I'm subscribed to a bug.

Worth a shot though as the system might have changed.
fixed.

[philinux]

fixed.

Ah nice. Shame the other won't play ball.

[sandyd]

you know that this can't be fixed without the op :(