ramakris@bloss.cs.vt.edu (S Ramakrishnan) (01/26/91)
I always thought 'su' was a 'substitute user' command. Its seems
apt also, since it allows the current USER to be changed to the
specified user-id. Of course, default value of this parameter is
root.
That being so, why do so many reputed (?) shell programming books
describe 'su' as 'super user' command ('becoming a super user -- su').
Was it originally meant to be become-superuser command ?
--
S.Ramakrishnan, CS Dept, McBryde Hall, VaTech, Blacksburg, Virg. 24061-0106
(Email : Internet : ramakris@bloss.cs.vt.edu )
( UUCP : padma@topsy.UUCP )hunt@dg-rtp.rtp.dg.com (Greg Hunt) (01/27/91)
In article <868@creatures.cs.vt.edu>, ramakris@bloss.cs.vt.edu (S Ramakrishnan) writes: > I always thought 'su' was a 'substitute user' command. Its seems > apt also, since it allows the current USER to be changed to the > specified user-id. Of course, default value of this parameter is > root. > > That being so, why do so many reputed (?) shell programming books > describe 'su' as 'super user' command ('becoming a super user -- su'). > Was it originally meant to be become-superuser command ? It's because the default operation of su, as you mention, is to become root, who is the super user. Using the su command to become the super user is more common, in my opinion, than using it to become another user. That's my understanding of the origin of the name. The man page for my system says "su - become super-user or another user", which is clearer than what you listed from your man page. "Super user" is defined as having a user-id of zero. Both root and sysadm usually have a user-id of zero, so both user names have super user privileges. Also, su doesn't change the current "user" as you mention. Rather, it starts a new shell with the specified user name. When you exit this new shell, you're back running your original shell. At least, that's the way it works on my system. Hope this helps. Enjoy! -- Greg Hunt Internet: hunt@dg-rtp.rtp.dg.com DG/UX Kernel Development UUCP: {world}!mcnc!rti!dg-rtp!hunt Data General Corporation Research Triangle Park, NC, USA These opinions are mine, not DG's.
guy@auspex.auspex.com (Guy Harris) (01/27/91)
>> Was it originally meant to be become-superuser command ? > >It's because the default operation of su, as you mention, is to become >root, who is the super user. And because, as I remember, the V6 version *only* let you become super-user; it didn't take an optional "who should I become" argument. Back then, it *was* the "super user" command; I guess when they added the user-name argument, they came up with "substitute user" as the best, well, umm, what *is* the name for a phrase formed from an acronym? :-) (Remember, the etymology of UNIX commands is, at times, quirky. Consider V6's "dsw" command - no, it's not "Department of Sanitary Waste", nor is it roughly based on "Do Svidanja".)
cornett@seattle.crd.ge.com (dan cornett) (01/28/91)
The "su" does not stand for super-user; this meaning is given it by those who do not have experience with UNIX. "substitute user" is close to the meaning: "set user" or "set userid" (I saw both used in the earliy 80's, but I no longer have the old man pages, so I have forgotten which was the "official" meaning.) The optional userid argument is of main use to root. Root can su to any other user without knowing the password; this facilitates helping other users when the system operator is working as root and one of the system users says "such and such isn't working in my account." Side note: this is why root and system operators should make "." the last directory searched (or better, do not include "." in the search path). su has been the source of many Trojan horse attacks by users who ask for "help" which requires an su. Danny
mike@wang.com (Mike Sullivan) (01/29/91)
su stands for Set-User -- ________________________ / __ \ | Michael J. Sullivan |ec.lec.tic adj Choosing | \ \ / /\ |\ | / ` | | Wang Laboratories Inc. |or consisting of what | \/ \/ /--\ | \| \__T | | mike@WANG.COM |appears to be the best \________________________/ | |from diverse sources.
skwu@spot.Colorado.EDU (WU SHI-KUEI) (01/29/91)
My V7 manual reads: su - substitute user id temporarily System III and later: su - become super-user or another user You takes your choice or makes a pick (:-)
jerry@ora.com (Jerry Peek) (01/29/91)
In article <1991Jan26.173253.21396@dg-rtp.dg.com> hunt@dg-rtp.rtp.dg.com writes: > ...Using the su command to become the > super user is more common, in my opinion, than using it to become > another user. That's my understanding of the origin of the name. BTW, here's why I use "su user" a lot. I think it's really handy: - I want shells open onto several other accounts. My system has job control, so I can suspend the "su user" shells and jump back to them whenever I want: jerry@wheeze% jobs [1] Stopped su [2] + Stopped su bin [3] - Stopped su manuals jerry@wheeze% fg su bin ...do stuff as bin... bin@wheeze% suspend Stopped jerry@wheeze% fg %1 su wheeze# ...do stuff as root... wheeze# suspend Stopped jerry@wheeze% - Because these shells run on the same tty as your login shell, "su" doesn't tie up other tty/pty ports like multiple logins or multiple windows can. This is a help on busy machines with lots of users. The thing to watch out for is that plain "su user" doesn't read a csh user's .login file or sh user's .profile. Using "su - user" solves that, but you can't suspend an "su -" shell (at least not on my systems). --Jerry Peek, jerry@ora.com
cdl@chiton.ucsd.edu (Carl Lowenstein) (01/31/91)
In article <1991Jan29.182919.24062@dg-rtp.dg.com> goudreau@larrybud.rtp.dg.com (Bob Goudreau) writes: > >Anyone know what the v6 or v7 man pages said? Ok, already. I just went to the back bookshelf and found: - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - SU(VIII) 10/31/73 SU(VIII) NAME su -- become privileged user SYNOPSIS su DESCRIPTION Su allows one to become the super-user, who has all sorts of marvelous (and correspondingly dangerous) powers. . . . - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -- carl lowenstein marine physical lab u.c. san diego {decvax|ucbvax} !ucsd!mpl!cdl cdl@mpl.ucsd.edu clowenstein@ucsd.edu
dmturne@PacBell.COM (Dave Turner) (01/31/91)
In article <1991Jan29.182919.24062@dg-rtp.dg.com> goudreau@larrybud.rtp.dg.com (Bob Goudreau) writes: >Anyone know what the v6 or v7 man pages said? The UNIX Programmer's Manual Sixth Edition (by Thompson and Ritchie), May, 1975 says on man page: su(VIII) su - become privileged user The UNIX User's Manual Release 3.0 (based on the UPM Seventh Edition), June, 1980 says on man page: su(1) su - become super-user or another user The old manuals were more fun to read. For su in the sixth edition it says: "Su allows one to become the super-user, who has all sorts of marvelous (and correspondingly dangerous) powers." -- Dave Turner 415/823-2001 {att,bellcore,sun,ames,decwrl}!pacbell!dmturne
scjones@thor.UUCP (Larry Jones) (01/31/91)
In article <1991Jan29.182919.24062@dg-rtp.dg.com>, goudreau@larrybud.rtp.dg.com (Bob Goudreau) writes: > The "substitute user" phrase might be Berkeley-derived; both the > 4.2 and 4.3 BSD man pages summarize the command as "su -- substitute > user id temporarily". > > Anyone know what the v6 or v7 man pages said? My v7 man page says "substitute user id temporarily". ---- Larry Jones, SDRC, 2000 Eastman Dr., Milford, OH 45150-2789 513-576-2070 Domain: scjones@thor.UUCP Path: uunet!sdrc!thor!scjones My life needs a rewind/erase button. -- Calvin
rbj@uunet.UU.NET (Root Boy Jim) (02/01/91)
In article <687@chiton.ucsd.edu> cdl@chiton (Carl Lowenstein) writes: ?In article <1991Jan29.182919.24062@dg-rtp.dg.com> goudreau@larrybud.rtp.dg.com (Bob Goudreau) writes: ?> ?>Anyone know what the v6 or v7 man pages said? ? ?Ok, already. I just went to the back bookshelf and found: Presumably from the Sixth Edition (V6). ?- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - ? ?SU(VIII) 10/31/73 SU(VIII) ? ?NAME ? su -- become privileged user ? ?SYNOPSIS ? su ? ?DESCRIPTION ? Su allows one to become the super-user, who has all sorts of ? marvelous (and correspondingly dangerous) powers. . . . ? ?- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Well, I have a Fifth Edition manual. It has the same date and the exact text listed above, except that it is in section I, not VIII. The Preface says the number of installations in "now above 50". -- Root Boy Jim Cottrell <rbj@uunet.uu.net> Close the gap of the dark year in between