Accounts and Permissionsλ︎
Linux file system access is based on user account and group account membership.
Read, Write and eXecute authorisation is defined with respect to the user (u), group (g) and all accounts (a)
whoami shows the currently-logged in user account name.
Elevated privilegesλ︎
su switch to another user account, allowing different access permissions for the file system. su is most commonly used to switch to the root user account.
The operating system prompts for the account password that is being accessed.
sudo temporarily elevates privileges to that of the root account, allowing access to files and commands that would otherwise be declined.
For example, run the Debian Linux apt tool to update software versions.
Change access permissionsλ︎
chmod changes access permissions of files or directories: chmod [options] [permission] [file-or-directory]
Set owner access to read, write and access directories.
Set permissions literally:
The second, third and fourth position sets permission for the owner. The next three the group and last three any other user.
Directory and file permissions
read (r), write (w), and execute (x)
owner (u), a group (g), or other (o) accounts
Change ownershipλ︎
chown changes ownership of files, directories or symbolic links: chown [options] newowner:newgroup file1 file2
Assign a user as the new owner of an item. Leave the group name empty to set the same as the user account.
Omit user account name to make all group members the owner
Account managementλ︎
useradd creates a new account or update groups assigned to a user: useradd [options] new_username
By default, the useradd command doesn’t prompt you to give the new user a password. You can add or change it manually later with the passwd command:
passwd new_username
userdel deletes a given account name and requires elevated privileges
To set up a password and other details during the account creation process, use the adduser command instead.