【精品资料】sudo.pptVIP

Sudo Yi-Hsiang Lin yslin@.tw 2002/5/21 @ CISCC OUTLINE Introduction Related files of command “sudo” The options of command “sudo” Examples of command “sudo” The file formats of “sudoers”grammar, aliases Examples of file “sudoers” entries Introduction Sudo allows a permitted user to execute a command as the superuser or another user Sudo use user’s password When authenticated, a timestamp is used. User can use sudo without a password for 5 minutes log both successful and unsuccessful Related files of sudo sudo : under /usr/bin or /usr/local/bin- execute a command as another user sudoers: under /etc or /usr/local/etc- list of which users may execute what visudo: under /usr/sbin or /usr/local/sbin- edit the sudoers file /var/run/sudo:Directory containing timestamps The options of sudo(1/2) -V: Version -l: list allowed commands -L: list defaults – Defaults parameters -h: help -v: validate – update timestamp -k: kill – invalidate timestamp -K: sure kill – remove timestamp entirely The options of sudo(2/2) -b: background -p: prompt – override the default prompt -c: class -a: authentication -u: user – username or #uid -s: shell -H: HOME -S: stdin Examples of sudo Listing of an unreadable directory% sudo ls /usr/local/protected List home dir. of ~zjm which is not exported as root:% sudo -u zjm ls ~zjm Edit the index.html file as user www% sudo -u www vi ~www/htdocs/index.html Shutdown a machine% sudo shutdown -r +15 quick reboot“ runs the commands in a subshell to make the cd and file redirection work% sudo sh -c cd /home ; du -s * | sort -rn USAGE The file formats of “sudoers” – grammar GRAMMAR:Use Extended Backus-Naur Form (EBNF) symbol ::= definition | alternate1 | alternate2 ...? : Means that the preceding symbol is optional. It may appear once or not at all* : Means that the preceding symbol may appear zero or more times.+ : Means that the preceding symbol may appear one or more times. The file formats of “sudoers” – aliases four kinds