Ubuntu – How to get permissions to edit system configuration files

configurationpermissionsroot

I can't seem to edit and save config files in the root system (eg: /etc/dhcp/dhcpd.config); it just says "permission denied" or the save option is blocked in the text editor.

I'm pretty sure I'm a root user, but how do I make sure? If I am a root user, how do I fix this?

Best Answer

Which text editor are you using? If you are a root user and know the password, try (in a terminal) either:

sudoedit /etc/dhcp/dhcpd.config if you are using a terminal-based editor such as nano or are ssh'ing into a server.
gksudo <text editor here> /etc/dhcp/dhcpd.config if you are using a GUI-based editor such as gedit

In either case, you'll need to first provide your root password when requested.

In Ubuntu 14.04 onwards, gksudo is not installed by default. You will have to install the gksu package (either from the Software Centre or via sudo apt-get install gksu) to get it.

In Ubuntu 17.10, Wayland is default instead of the traditional X server, and running graphical editors as root is difficult. See Why don't gksu/gksudo or launching a graphical application with sudo work with Wayland? for details.

In Ubuntu 18.04, gksudo is not available in the official repositories. Use sudo -H <text editor> instead, or the admin:// protocol:

gedit admin:///etc/dhcp/dhcpd.config

Mount a FAT32 partition in a USB stick with write permissions for everybody

Assumption: the pendrive is seen as /dev/sdx, replace the partition device sdxn with the actual letters for the partition, for example sdb1: /dev/sdxn ---> /dev/sdb1.

Explanation: x is the drive letter, and n is the partition number. Text after # is a comment (not used as a command).

sudo mkdir -p /mnt/sd1  # only if you want a new mountpoint
sudo umount /dev/sdxn   # general: only if already mounted (with bad permissions).
sudo umount /dev/sdb1   # example

sudo mount -o rw,users,umask=000 /dev/sdxn /mnt/sd1  # general: mount
sudo mount -o rw,users,umask=000 /dev/sdb1 /mnt/sd1  # example

ls -ld /mnt/sd1                          # check permissions

sudo bash -c "echo 'Hello World' > /mnt/sd1/hello.txt"  # test writing with sudo
cat /mnt/sd1/hello.txt                   # test reading (as user)
ls -l /mnt/sd1                           # check permissions of the content
rm /mnt/sd1/hello.txt                    # test removing (as user)
echo 'I am a user' > /mnt/sd1/user.txt   # test writing (as user)

Best Answer

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Mount a FAT32 partition in a USB stick with write permissions for everybody

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