The first time you turn on the virtual network adapter (TUN) in the Linux app, it needs administrator rights and asks you to "enter the admin password". The app then uses sudo to authorize the 5UF core (it makes root the owner and adds the setuid bit), after which the core can create the virtual adapter.
Which password is this?
The password is passed to sudo, so on Ubuntu, Debian and most other systems it's your own login password, not the root password. If you normally run sudo with your own password, just enter it in the dialog.
When do you need the command line?
• On a company or school computer where sudo is set up without a password (NOPASSWD); the dialog won't accept an empty password.
• You don't know any administrator password, but you're allowed to use sudo or sudo -i to become root.
• The dialog keeps saying the password is wrong.
In these cases you can authorize the core yourself in a terminal. Afterwards the app sees it as authorized and won't ask for a password again.
Steps (deb / rpm packages):
1. Quit 5UF VPN completely (choose Quit from the tray icon).
2. Open a terminal and run these two commands. The packages install the core at /usr/share/wufclub/5UFClashCore:
sudo chown root:root /usr/share/wufclub/5UFClashCore sudo chmod +sx /usr/share/wufclub/5UFClashCore
If you've already switched to root with sudo -i or sudo su -, run them without the leading sudo.
3. Check the result:
stat -c '%U:%G %A' /usr/share/wufclub/5UFClashCore
Output like root:root -rwsr-sr-x (starting with root and containing rws) means it worked.
4. Open 5UF VPN again, choose "Tun" or "System proxy+TUN" mode in Settings and connect. It won't ask for a password any more.
Can't find the file? Use these commands to locate the core, then use that path in the commands above:
dirname "$(readlink -f "$(command -v wufclub)")" sudo find / -name 5UFClashCore -type f 2>/dev/null
AppImage: an AppImage is mounted read-only while it runs, so the core inside it can't be authorized. If you need the virtual adapter, we recommend the deb or rpm package instead. Alternatively, run ./5UF_VPN-xxx.AppImage --appimage-extract, run the two commands above on 5UFClashCore inside the extracted squashfs-root folder, then start squashfs-root/AppRun.
Notes:
• After every upgrade or reinstall the core file is replaced and loses the setuid bit, so run the commands again (or enter the password in the dialog).
• Once authorized, the core runs with root rights, which is required to create the virtual adapter. Only do this on computers you trust, and on a company computer, ask your administrator first.
• To undo it, run sudo chmod -s /usr/share/wufclub/5UFClashCore.
• If you don't need the virtual adapter, System proxy mode needs no administrator rights, although programs that ignore the system proxy won't go through the VPN.
