Notes

chown<newuser>pathname the root user can change the owner of the file <pathname> to the <newuser> by executing this command
the newgrp command can be used to change the groups and save all the new files in the new groups
the chgrp command can be used save a file in a different group temporarily
chmod is used to change the permissions for a file or a directory. Only the root user or the owner of the file can do this.
chmod has symbolic and octal ways of changing permissions. Octal method involves remembering the numbers but it is more useful for changing more than one set of permissions
symbolic method
u user,g group,o others,a all
+ add,- remove,= specify the exact permission
r=read,w=write,x=execute and name of the filename you want to change permissions for at last
To specify permissions for more than one set use commas and not spaces
Octal method
read(r)=4
write(w)=2
execute(x)=1
all permissions =7
the name of the file you want to change permissions for at last
read permissions= read and copy
read and write= remove the file
setuid on a file (Octal value 4000) cause an executable file to run under user owner identity instead of user running it. (s replaces x user owner permissions)
setgid on a file (Octal value 2000) causes the file to run under group owner identity rather than user running it. (s replaces x group owner permissions)
setgid on directory (Octal value 2000) causes new files and directories that are created inside to be owned by the group that owns the directory (s replaces x group owner permissions)
sticky on a directory (Octal value 1000) causes files inside a directory to be only removed by user owner or root user. (t replaces x on other permissions)