mjhjmtu

I am analyzing one script and I cannot find online what chgrp 0 mean in the following line:

find $1 -follow -exec chgrp 0 

so

find $1 takes parameter,

-follow causes find to follow symlinks,

-exec executes the command,

chgrp 0 change group ownership, but what 0 do?,

for all items found by the find command.

Please correct me if I am wrong with something.

chgrp 0 file will change the group ownership of the file file to the group with GID 0 which in nearly all cases in Linux is the root group (in BSD, this is nearly always wheel). So your find command will search in the path provided by the first positional parameter ($1) for all filesystem objects contained therein, follow any symbolic links to their targets, and make the group owner of those objects GID 0, root (or wheel).

Basicly ownership of any file/directory in linux is stored in the in inode. And it stored as an integers (integer for user, and second integer for group). It depends only on your NSS (e.g. /etc/passwd file, or ldap) which name it will show you in ls. Performing operation like chgrp root file system will take GID of "root" group (in my case it's 0) and write that 0 into inode. You can also make something like this:

# touch testfile
# chgrp 135543 testfile
# ls -l testfile
-rw-r--r--. 1 root 135543 0 Aug 21 18:05 testfile
# groupadd -g 135543 testgroup
# ls -l testfile
-rw-r--r--. 1 root testgroup 0 Aug 21 18:05 testfile

0 is the UID and GID of root. So as you are executing chgrp 0 you are changing the group ownership of the file/directory to root.