Permission Denied When Trying to Append a File to a Root Owned File with Sudo

Permission denied when trying to append a file to a root owned file with sudo

Run bash as sudo:

$ sudo bash -c "cat add_file >> /etc/file"

$ whoami;sudo bash -c "whoami";whoami
iiSeymour
root
iiSeymour

Why sudo cat gives a Permission denied but sudo vim works fine?

The problem is that the redirection is being processed by your original shell, not by sudo. Shells are not capable of reading minds and do not know that that particular >> is meant for the sudo and not for it.

You need to:

quote the redirection ( so it is passed on to sudo)
and use sudo -s (so that sudo uses a shell to process the quoted redirection.)

How do I use sudo to redirect output to a location I don't have permission to write to?

Your command does not work because the redirection is performed by your shell which does not have the permission to write to /root/test.out. The redirection of the output is not performed by sudo.

There are multiple solutions:

Run a shell with sudo and give the command to it by using the -c option:
```
sudo sh -c 'ls -hal /root/ > /root/test.out'
```
Create a script with your commands and run that script with sudo:
```
#!/bin/sh
ls -hal /root/ > /root/test.out
```
Run sudo ls.sh. See Steve Bennett's answer if you don't want to create a temporary file.

Launch a shell with sudo -s then run your commands:

[nobody@so]$ sudo -s
[root@so]# ls -hal /root/ > /root/test.out
[root@so]# ^D
[nobody@so]$

Use sudo tee (if you have to escape a lot when using the -c option):
```
sudo ls -hal /root/ | sudo tee /root/test.out > /dev/null
```
The redirect to /dev/null is needed to stop tee from outputting to the screen. To append instead of overwriting the output file
(>>), use tee -a or tee --append (the last one is specific to GNU coreutils).

Thanks go to Jd, Adam J. Forster and Johnathan for the second, third and fourth solutions.

Append content to a ROOT file with bash?

From sh man page:

Enclosing characters in single quotes preserves the literal value of
each character within the quotes. A single quote may not occur
between single quotes, even when preceded by a backslash.

Try:

sudo sh -c "echo -e \"foo\nbar\" >> toto"

Use sudo to change file in root directory

The sudo command executes the command you give it under the root account. In its simplest form, the syntax is:

sudo command args...

For example:

sudo whoami

prints root.

If you type, as you did in your question:

sudo "nameserver 8.8.8.8" >> /etc/resolv.conf

then it's not going to work; it will try to execute a command named "nameserver 8.8.8.8", which doesn't exist. The problem there is that you're missing the echo command.

This:

sudo "echo nameserver 8.8.8.8" >> /etc/resolv.conf

still won't work because there's no command called "echo nameserver 8.8.8.8". That entire string is passed to sudo as a single argument. It needs to see the command and each of its arguments as a separate argument.

So this:

sudo echo nameserver 8.8.8.8 >> /etc/resolv.conf

is getting closer -- but it still won't work. It executes the echo command as root -- but echo requires no special privileges, so there's no point in executing it as root. The >> /etc/resolv.conf redirection is executed by your shell, which is running as you, not as root. Since you don't have permission to write to /etc/resolv.conf, the command fails. The sudo command never sees the redirection.

You need the redirection to be executed under the root account, which means that you need a shell process running as root. So the solution is:

sudo sh -c 'echo nameserver 8.8.8.8 >> /etc/resolv.conf'

This launches a shell as a root process. That shell executes the command line echo nameserver 8.8.8.8 >> /etc/resolv.conf. Since you have a root shell executing both the echo and the output redirection, it should work.

(I suggest grabbing a copy of your /etc/resolv.conf file before doing this, just to make sure you can recover if you accidentally clobber it.)

Bash / Linux Permissions denied as SUDO

The second line of your "working" example is executed in a new shell that already runs with root privileges, since sudo -s starts a new shell.

But the :> in your shell script will be executed by the shell and not by sudo, so it will run with the original (presumably lower) privileges.

The workaround is to pipe the output of something like echo to a command using sudo: echo | sudo tee "$DOCKER_LOG_PATH".

An even simpler and more explicit solution is to use a command that's explicitly built to truncate files: sudo truncate -s0 "$DOCKER_LOG_PATH".

`sudo` to append to file with root permissions (inside `system(3)` from C)

Structured as you have it, the redirection is evaluated outside the sudo operation, and therefore does not have root privileges and cannot open /etc/network/interfaces for writing. You need to do it like this instead:

system("sudo /bin/sh -c \"echo 'iface wlan0 inet dhcp' >> /etc/network/interfaces\"");

so that the redirection is evaluated by the shell inside the sudo.

(Also, you can't nest single quotes inside single quotes.)

How to write a file with sudo privileges in Python?

Following solution worked for me finally. I created a new file called etcedit.py which will write to the file.

os.system("echo %s| sudo -S python etcedit.py %s"  % ('rootpassword', 'host_name'))

My etcedit.py file

import os, subprocess
import sys
from sys import argv

def etc_update(host_name, *args):
    path = "/etc/hosts"
    host_name = host_name[0]
    fw = open(path,'w')
    fw.write(host_name)

etc_update(sys.argv[1:])

This works!

Permission Denied When Trying to Append a File to a Root Owned File with Sudo