How to get root permission?


#1

when i try to set a led.
morning2050@localhost:/sys/class/leds/fantem:led3_red:status$ sudo echo 1>brightness
-bash: brightness: Permission denied
morning2050@localhost:/sys/class/leds/fantem:led3_red:status$ Permission denied^C
morning2050@localhost:/sys/class/leds/fantem:led3_red:status$ ls
brightness device max_brightness power subsystem trigger uevent
morning2050@localhost:/sys/class/leds/fantem:led3_red:status$ su root
Password:
su: Authentication failure
morning2050@localhost:/sys/class/leds/fantem:led3_red:status$ su root
Password:
su: Authentication failure

i can not get root permission.


#2

this is ubuntu … use sudo -s


#3

thankyou for fast reply,it works


#4

i assume this is on Ubuntu Core so I’ll move this post to the right category (feel free to change it again if I’m wrong)


#5

Hi,

what is the default password of root?

colinliao@localhost:~$ su -s root
Password:
su: Authentication failure
colinliao@localhost:~$


#6

there is no password, the root account is completely locked down (with a readonly passwd file) … the user you create in the first-boot wizard is a sudo user though … simply use sudo -s after ssh’ing into the device if you really think you require a root shell …


#7

as a point of interest, the reason your command sudo echo 1>brightness fails is because it is executed as follows:

  • as the unprivileged user
  • take the output of the command sudo echo in the pipe named 1
    • because you wrote 1>brightness not 1 >brightness then it is naming the pipe, which you likely didn’t intend
    • you likely meant echo 1 >brightness which prints the number 1 into stdout and redirects that into brightness
  • write that output of pipe 1 from the sudo command into ./brightness as the original unprivileged user

To correctly use echo to write into a file that can only be written-to by root you need to use a different method such as:

echo 1 | sudo tee brightness

or

sudo -c "echo 1 > brightness"

or spawn a root shell like @ogra suggested with sudo -s or sudo -i.