group 'engineers', attempts to delete the file named 'tekken' but he cannot, since he is not the owner. Without sticky bit, 'wozniak' could have deleted the file, because the directory named 'videogames' allows read and write by 'engineers'. A default use of this can be seen at the /tmp folder. [ torvalds /home/shared/ ] $ groups torvalds torvalds : torvalds engineers [ torvalds /home/shared/ ] $ stat -c "%a %U:%G %n" ./videogames/ 1770 torvalds:engineers ./videogames/ [ torvalds /home/shared/ ] $ echo 'NEW FILE' > videogames/tekken [ torvalds /home/shared/ ] $ su - wozniak Password: [ wozniak ~/ ] $ groups wozniak wozniak : wozniak engineers [ wozniak ~/ ] $ cd /home/shared/videogames [ wozniak /home/shared/videogames/ ] $ rm tekken rm: cannot remove ‘tekken’: Operation not permitted Sticky bit with SGID 3171 on a directory named 'blog' owned by the group 'engineers' and the user 'root' A user named 'torvalds' who belongs primarily to the group 'torvalds' but secondarily to the group 'engineers' creates a file or directory named 'thoughts' inside the directory 'blog'. A user named 'wozniak' who also belongs to the group 'engineers' cannot delete, rename, or move the file or directory named 'thoughts', because he is not the owner and the sticky bit is set. However, if 'thoughts' is a file, then 'wozniak' can edit it. Sticky bit has the final decision. If sticky bit and SGID had not been set, the user 'wozniak' could rename, move, or delete the file named 'thoughts' because the directory named 'blog' allows read and write by group, and wozniak belongs to the group, and the default 0002 umask allows new files to be edited by group. Sticky bit and SGID could be combined with something such as a read-only umask or an append only attribute.[ torvalds /home/shared/ ] $ groups torvalds torvalds : torvalds engineers [ torvalds /home/shared/ ] $ stat -c "%a %U:%G %n" ./blog/ 3171 root:engineers ./blog/ [ torvalds /home/shared/ ] $ echo 'NEW FILE' > ./blog/thoughts [ torvalds /home/shared/ ] $ su - wozniak Password: [ wozniak ~/ ] $ cd /home/shared/blog [ wozniak /home/shared/blog/ ] $ groups wozniak wozniak : wozniak engineers [ wozniak /home/shared/blog/ ] $ stat -c "%a %U:%G %n" ./thoughts 664 torvalds:engineers ./thoughts [ wozniak /home/shared/blog/ ] $ rm thoughts rm: cannot remove ‘thoughts’: Operation not permitted [ wozniak /home/shared/blog/ ] $ mv thoughts /home/wozniak/ mv: cannot move ‘thoughts’ to ‘/home/wozniak/thoughts’: Operation not permitted