# User, file and group permissions ## Info Show all groups a user belongs to ``` groups ``` Show primary groups for user ``` id ``` ## Sudo Perform a command as the super user ``` sudo ``` ## Switch users Switch to specific user ``` su ``` Switch to root or specific user and load user profile (`CTRL + d` to exit user mode) ``` su - su - ``` ## Managing users Create a new user ``` adduser ``` Change password for active user ``` passwd ``` ## File permissions Change file mode and access control ``` chmod ``` Permission types ``` r = read w = write x = execute ``` Numerical values ``` r = 4 w = 2 x = 1 ``` Permission groups ``` u = user g = group o = other a = all (sets u, g and o) ``` ### Set permissions with assigment Set user to rwx, group to rw and other to r ``` chmod u=rwx,g=rw,o=r ``` Set u to rwx, group and other to r ``` chmod u=rwx,go=r ``` ### Alter some permission with plus and minus Add write permissions to user group ``` chmod g+w ``` Remove read and write permission from other group ``` chmod o-rw ``` Add execute for user, remove write for group, remove rwx for other ``` chmod u+x,g-w,o-rwx ``` ### Use -R to set permissions recursively Set group to read and write for the directory and all sub files and folders ``` chmod -R g=rw ``` ### Set user / group for new files Set group automatically when creating new files within `` via the `g+s` SETGID (SET Group ID) flag ``` chmod g+s ``` Remove setting group automatically for new files within `` by removing set group flag ``` chmod g-s ``` ## Managing groups and owners List available groups ``` less /etc/group ``` Modify a user (usermod) and add (-a) them to a group (-G) ``` usermod -a -G ``` Change file group associated with the file permissions ``` chgrp ``` Change file owner ``` chown ``` ## Cleaning up file permissions Find files with permission set to 777 and change them to default 644 ``` find . -type f -perm 777 -print0 | xargs -0 chmod 644 ``` Find directories with permission set to 777 and change them to default 755 ``` find . -type d -perm 777 -print0 | xargs -0 chmod 755 ``` Unlock all locked files found under the current directory ``` chflags -R nouchg * ``` --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://refdocs.buymeasoda.com/unix/user-file-and-group-permissions.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.