1. In OS X Yosemite and earlier,

When you have a trouble with the disk in your Mac, you may check if it has the right permission in the system files.

You can check easily by

 sudo diskutil repairPermissions /

or Launch Disk Utility ->Select the Disk you want to repair -> Select “First Aid” -> Click “Repair Disk Permissions”

If your “sudo” fails, you can recover it by this

1. Enable root
   1. System Preference -> User & Groups -> Login Options -> Network Account Server -> Open Directory Utility …
   2. Select “Edit” -> “Enable Root User”
   3. System Preference -> User & Groups -> Select “Show fast user switching menu as “Full Name”
   4. Then, you can switch root easily.
2. Login as root or switch to root.
3. Open Terminal
4. chmod 4755 /usr/bin/sudo
5. Done.

2. In OS X El Captain or later,

I’ve referred from How to Verify & Repair Permissions in OS X El Capitan

– Verify a permission error

sudo /usr/libexec/repair_packages --verify --standard-pkgs /

– Repair the permission errors

sudo /usr/libexec/repair_packages --repair --standard-pkgs --volume /