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unix permissions

Trying to grasp the concept of permissions in Unix.

ie: xxx-xxx-xxx

1. I know that the first part applies to the permissions the owner gets on the file
The second part applies to the group <---this is where I'm lost
The third part applies to everyone else.

So a ping chmod 700 /sbin/ping, will deny ping to everyone but the owner
What would a 770 /sbin/ping do?

2. If you have r/w access to a file, do you need "execute" permission as well?

Thanks

ASKER CERTIFIED SOLUTION

Kent Olsen

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dissolved

ASKER

thanks, I'm giving you the question.

Can you clarify 2 quick things for me?

1.How do you tell group membership? ie: How do I tell what users belong to /sbin/ping?

2. What groups belong to /sbin/ping by default?

Thanks!

Kent Olsen

1) Enter:

ls -l /sbin/ping

You'll get a line that looks like:

-r-sr-xr-x 1 root system 31862 <date> ping

This shows that ping is owned by 'root' and is a member of group 'system'

Note that not all systems use the /sbin/ping path. AIX uses /usr/sbin/ping.

2) It's semantics, but groups don't belong to files. Users belong to groups and a file is a member of a group.

Most system executables will belong to group 'bin' or 'system'. In AIX ping belongs to 'system' by default. This may differ with other implementations of unix.

Kent