Su sudo9/17/2023 ![]() ![]() Note: The most customized option should go at the end of the file, as the later lines overrides the previous ones. To allow members of group wheel sudo access: To allow a user to run all commands as any user but only on the machine with hostname HOST_NAME: To allow a user to gain full root privileges when they precede a command with sudo, add the following line: # Set default EDITOR to restricted version of nano, and do not allow visudo to use EDITOR/VISUAL.ĭefaults editor=/usr/bin/rnano, !env_editor To change the editor of choice permanently system-wide only for visudo, add the following to /etc/sudoers (assuming nano is your preferred editor): To change the editor permanently, see Environment variables#Per user. This might come in handy in case you want to circumvent locking the file with visudo. To establish nano as the visudo editor for the duration of the current shell session, export EDITOR=nano to use a different editor just once simply set the variable before calling visudo:Īlternatively you may edit a copy of the /etc/sudoers file and check it using visudo -c /copy/of/sudoers. The sudo package is compiled with -with-env-editor and honors the use of the SUDO_EDITOR, VISUAL and EDITOR variables. visudo(8) warns that configuring visudo to honor the user environment variables for their editor of choice may be a security hole, since it allows the user with visudo privileges to run arbitrary commands as root without logging simply by setting that variable to something else.Always edit it with visudo to prevent errors. It is imperative that sudoers be free of syntax errors! Any error makes sudo unusable.To use sudo, simply prefix a command and its arguments with sudo and a space: To begin using sudo as a non-privileged user, it must be properly configured. Sudo can also be used to run commands as other users additionally, sudo logs all commands and failed access attempts for security auditing. By enabling root privileges only when needed, sudo usage reduces the likelihood that a typo or a bug in an invoked command will ruin the system. Unlike su, which launches a root shell that allows all further commands root access, sudo instead grants temporary privilege elevation to a single command. Sudo is an alternative to su for running commands as root. Last login: Fri Sep 22 22:07:45 2017 from .Sudo allows a system administrator to delegate authority to give certain users-or groups of users-the ability to run commands as root or another user while providing an audit trail of the commands and their arguments. If we change user dong’s login shell to /sbin/nologin, ssh will fail: $ ssh -l dong hydra sshĪs expected, ssh does honor /sbin/nologin in the password database. However, if we use the -i option to simulate initial login, sudo will run the shell specified by the password database entry of the target user as a login shell, in this case, /sbin/nologin: ~]# sudo -u adm -i id For example: ~]$ su -s /bin/bash -c pwd ~]$ su -s /bin/bash -c pwd admīy contrast, sudo doesn’t honor /sbin/nologin in /etc/passwd: ~]# sudo -u adm id If we give adm a password, we can even su to adm from an unprivileged user. Uid=3(adm) gid=4(adm) ~]# su -s /bin/bash -c pwd adm Uid=3(adm) gid=4(adm) ~]# su -s /bin/bash -c pwd ~]# su -s /bin/bash -c id adm ![]() However, we can override the login shell in the password database, by supplying a shell (e.g., -s /bin/bash) in the CLI. This account is currently not ~]# su -c id adm If we try to use su to run a command with adm, it will fail, as expected. Su apparently honors entries in /etc/passwd. On a typical CentOS 7 installation, the login shell of user adm is /sbin/nologin (see /etc/passwd): adm: x: 3: 4: adm:/ var/ adm:/ sbin/ nologin su If a user’s login shell is /sbin/nologin, would su, sudo or ssh honor it? Let’s find it out. ![]()
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