UNIX Command RTFM: sudo(8)

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Presentation transcript:

UNIX Command RTFM: sudo(8) Gilbert Detillieux April 12, 2011 MUUG Meeting

What does sudo do?... Like su: run as substitute user But do: typically, run a specific command Safer than su: Don’t need to share root/admin passwords (authentication via invoking user’s password) Can only do what’s been specifically granted (role-based access control) in sudoers file Logs failures and successful commands

What sudo doesn’t do... Doesn’t allow what hasn’t been granted Doesn’t override file/directory permission Doesn’t affect your current shell/environment: Can’t do this: sudo cd /private/dir Doesn’t make non-executables executable Doesn’t turn your system into Ubuntu!

sudo(8) Man Page NAME SYNOPSIS sudo, sudoedit – execute a command as another user SYNOPSIS sudo -l[l] [-g groupname|#gid] [-U username] [-u username|#uid] [command] sudo [-g groupname|#gid] [-u username|#uid] [VAR=value] [-i | -s] [command] sudoedit [-g groupname|#gid] [-u username|#uid] file ...

sudo(8) Man Page (cont.) OPTIONS -l[l] list allowed (and forbidden) commands for invoking user (or user specified by -U) on current host Double up the “l” for longer format output -g sets primary group to groupname or gid -u runs as user specified by username or uid (instead of root) -i simulates initial login: Uses shell from passwd(5) Reads .profile/.login, etc. Initializes environment, leaving DISPLAY and TERM unchanged, setting (only) HOME, SHELL, USER, LOGNAME, and PATH -s runs shell specified by SHELL

sudo(8) Examples Interactive shell: sudo –i or sudo –s Specific command: sudo cat /etc/shadow Edit a file: sudo vi /etc/shadow sudoedit /etc/shadow

sudoers(5) Examples: # User privilege specification: # User_List Host_List = (Runas_List) Tag_Spec Cmnd root ALL=(ALL) ALL # Members of admin group may gain root privileges: %admin ALL=(ALL) ALL

sudoers(5) Examples: Cmnd_Alias CGIHELPER = /usr/local/sbin/cgihelper # Normally, require a tty, to not show password in clear… # ... but override for specific commands run by CGI scripts... Defaults!CGIHELPER !requiretty # Allows owner of particular CGI scripts to run # “helper” command as other users... webuser ALL=(ALL) NOPASSWD: CGIHELPER

sudoers(5) Examples: # Allow non-root user to mount a backup drive (/etc/fstab): LABEL=backup /mnt/backup ext3 rw,noauto,noatime,user 1 0 # Allow same user to fsck the drive (/etc/sudoers): backuser ALL=(root) NOPASSWD: /sbin/fsck LABEL\=backup backuser ALL=(root) NOPASSWD: /sbin/fsck -f LABEL\=backup # Also allow RAID admin on drive: backuser ALL=(root) /usr/bin/drobom

Questions?