torvalds ~ ] $ stat -c "%a %A" ~/test/ 1770 drwxrwx--T SUID 4701 on an executable file owned by 'root' and the group 'root' A user named 'thompson' attempts to execute the file. The executable permission for all users is set (the '1') so 'thompson' can execute the file. The file owner is 'root' and the SUID permission is set (the '4') - so the file is executed as 'root'. The reason an executable would be run as 'root' is so that it can modify specific files that the user would not normally be allowed to, without giving the user full root access. A default use of this can be seen with the /usr/bin/passwd binary file. /usr/bin/passwd needs to modify /etc/passwd and /etc/shadow which store account information and password hashes for all users, and these can only be modified by the user 'root'.[ thompson ~ ] $ stat -c "%a %U:%G %n" /usr/bin/passwd 4701 root:root /usr/bin/passwd [ thompson ~ ] $ passwd passwd: Changing password for thompson The owner of the process is not the user running the executable file but the owner of the executable file SGID 2770 on a directory named 'music' owned by the user 'root' and the group 'engineers' A user named 'torvalds' who belongs primarily to the group 'torvalds' but secondarily to the group 'engineers' makes a directory named 'electronic' under the directory named 'music'. The group ownership of the new directory named 'electronic' inherits 'engineers.' This is the same when making a new file named 'imagine.txt' Without SGID the group ownership of the new directory/file would have been 'torvalds' as that is the primary group of user 'torvalds'. [ torvalds ~ ] $ groups torvalds torvalds : torvalds engineers [ torvalds ~ ] $ stat -c "%a %U:%G %n" ./music/ 2770 root:engineers ./music/ [ torvalds ~ ] $ mkdir ./music/electronic [ torvalds ~ ] $ stat -c "%U:%G %n" ./music/electronic/ torvalds:engineers ./music/electronic/ [ torvalds ~ ] $ echo 'NEW FILE' > ./music/imagine.txt [ torvalds ~ ] $ stat -c "%U:%G %n" ./music/imagine.txt torvalds:engineers ./music/imagine.txt [ torvalds ~ ] $ touch ~/test [ torvalds ~ ] $ stat -c "%U:%G %n" ~/test torvalds:torvalds ~/test Sticky bit 1770 on a directory named 'videogames' owned by the user 'torvalds' and the group 'engineers'. A user named 'torvalds' creates a file named 'tekken' under the directory named 'videogames'. A user named 'wozniak', who is also part of the