'ps auwx' and 'top': inconsistent display?
Hello, I have a perl script that should work as follows: * check some parameters * drop privileges ( $> = ...; $) = ...;) * fork some other programs Now when I run this script and "ps auwx" thereafter, I see that the programs I forked are running under the user id that I specified in the script. When I run 'top' on the same machine, these programs appear to be running as root. What gives? The system is an OpenBSD 4.5/amd64 machine. -- Kind regards, --Toni++
[SOLVED, sort of] Re: 'ps auwx' and 'top': inconsistent display?
Hi, On Fri, 24.07.2009 at 15:09:23 +0200, Toni Mueller wrote: > I have a perl script that should work as follows: > * check some parameters > * drop privileges ( $> = ...; $) = ...;) it turned out that 'top' displayed the "real userid" which I didn't set, while 'ps' displayed the effective userid, which I set like above. This prompts more questions: Why is the "real userid" inherited when using 'fork' while being switched to a different user? -- Kind regards, --Toni++
Re: [SOLVED, sort of] Re: 'ps auwx' and 'top': inconsistent display?
On Sat, Aug 01, 2009 at 03:33:54PM +0200, Toni Mueller wrote: > Why is the "real userid" inherited when using 'fork' while being > switched to a different user? Why should fork touch user id's? Drop them properly yourself after forking. http://search.cpan.org/~tlbdk/Privileges-Drop-1.01/lib/Privileges/Drop.pm -- Jussi Peltola
Re: [SOLVED, sort of] Re: 'ps auwx' and 'top': inconsistent display?
Hi, On Sat, 01.08.2009 at 17:13:43 +0300, Jussi Peltola wrote: > Why should fork touch user id's? I was under the impression that only the effective userid should be inherited by a forked process, not the real user id. Also, the inconsistency in the display of the tools doesn't appear to be reflected in the man pages. > http://search.cpan.org/~tlbdk/Privileges-Drop-1.01/lib/Privileges/Drop.pm Thanks for the hint. Not knowing about that, I so far assigned to both uid and gid variables, and that seemed to do the trick. -- Kind regards, --Toni++
Re: [SOLVED, sort of] Re: 'ps auwx' and 'top': inconsistent display?
* Toni Mueller [2009-08-05 13:18]: > On Sat, 01.08.2009 at 17:13:43 +0300, Jussi Peltola wrote: > > Why should fork touch user id's? > > I was under the impression that only the effective userid should be > inherited by a forked process, not the real user id. *sigh* fork does not change uids. none of them. -- Henning Brauer, h...@bsws.de, henn...@openbsd.org BS Web Services, http://bsws.de Full-Service ISP - Secure Hosting, Mail and DNS Services Dedicated Servers, Rootservers, Application Hosting - Hamburg & Amsterdam
Re: [SOLVED, sort of] Re: 'ps auwx' and 'top': inconsistent display?
On Wed, Aug 5, 2009 at 4:10 AM, Toni Mueller wrote: > On Sat, 01.08.2009 at 17:13:43 +0300, Jussi Peltola wrote: >> Why should fork touch user id's? > > I was under the impression that only the effective userid should be > inherited by a forked process, not the real user id. Make a note that whatever source of information you got that from was wrong and should not be trusted. I suggest you read W. Richard Stevens's "Advanced Programming in the UNIX Environment". >> http://search.cpan.org/~tlbdk/Privileges-Drop-1.01/lib/Privileges/Drop.pm > > Thanks for the hint. Not knowing about that, I so far assigned to both > uid and gid variables, and that seemed to do the trick. Did you set $) to a string containing more than one number? If not, you're still wrong and should strongly consider using the module, which has been tested by others. Philip Guenther
Re: [SOLVED, sort of] Re: 'ps auwx' and 'top': inconsistent display?
On 2009-08-05, Philip Guenther wrote: > On Wed, Aug 5, 2009 at 4:10 AM, Toni Mueller wrote: >> On Sat, 01.08.2009 at 17:13:43 +0300, Jussi Peltola wrote: >>> Why should fork touch user id's? >> >> I was under the impression that only the effective userid should be >> inherited by a forked process, not the real user id. > > Make a note that whatever source of information you got that from was > wrong and should not be trusted. I suggest you read W. Richard > Stevens's "Advanced Programming in the UNIX Environment". Anyone know how important the changes between the first and second edition of this are? (The older one's a lot cheaper..)
Re: [SOLVED, sort of] Re: 'ps auwx' and 'top': inconsistent display?
On Fri, Aug 7, 2009 at 7:49 AM, Stuart Henderson wrote: > On 2009-08-05, Philip Guenther wrote: >> On Wed, Aug 5, 2009 at 4:10 AM, Toni Mueller wrote: >>> On Sat, 01.08.2009 at 17:13:43 +0300, Jussi Peltola wrote: Why should fork touch user id's? >>> >>> I was under the impression that only the effective userid should be >>> inherited by a forked process, not the real user id. >> >> Make a note that whatever source of information you got that from was >> wrong and should not be trusted. I suggest you read W. Richard >> Stevens's "Advanced Programming in the UNIX Environment". > > Anyone know how important the changes between the first and second edition > of this are? (The older one's a lot cheaper..) >From the 2nd Edition (excuse any typos): Page xxii Changes from the First Edition Rich's work holds up well. I've tried not to change his original vision for this book, but a lot has happened in 13 years. This is especially true with the standards that affect the UNIX programming interface. Throughout the book, I've updated interfaces that have changed from the ongoing efforts in standards organizations. This is most noticeable in Chapter 2, since its primary topic is standards. The 2001 version of the POSIX.1 standard, which we use in this revision, is much more comprehensive than the 1990 version on which the first edition of this book was based. The 1990 ISO C standard was updated in 1999, and some changes affect the interfaces in the POSIX.1 standard. A lot more interfaces are now covered by the POSIX.1 specification. The base specifications of the Single UNIX Specification (published by THe Open Group, formerly X/Open) have been merged with POSIX.1. POSI.1 now includes several 1003.1 standards and draft standards that were formerly published separately. Accordingly, I've added chapters to cover some new topics. Threads and multithreaded programming are important concepts because they present a cleaner way for programmers to deal with concurrency and asynchrony. The socket interface is now part of POSIX.1. It provides a single interface to interprocess communication (IPC), regardless of the location of the process, and is a natural extension of the IPC chapters. I've omitted most of the real-time interfaces that appear in POSIX.1. These are best treated in a text devoted to real-0time programming. Once such book appears in the bibliography. I've updated the case studies in the last chapters to cover more relevant real-world examples. For example, few systems these days are connected to a PostScript printer via a serial or parallel port. Most PostScript printers today are accessed via a network so I've changed the case study that deals with PostScript printer communication to take this into account. The chapter on modem communication is less relevant these days. So that the original material is not lost, however, it is available on the book's Wb site in two formats: PostScript (http:/www.apuebook.com/lostchapter/modem.ps) and PDF (... .pdf). The source code for the examples shown in this book is also available at www.apubook.com. Most of the examples have been run on four platforms: 1. FreeBSD 5.2.1, a derivative of the 4.4BSD release from the COmputer Systems Research Group at the University of California at Berkeley, running on an Intel Pentium processor 2. Linux 2.4.22 (the Mandrake 9.2 distribution), a free UNIX-like operating system, running on Intel Pentium processors 3. SOlaris 9, a derivative of Sysstem V Release 4 from Sun Microsystems, running on a 64-bit UltraSPARC IIi processor 4. Darwin 7.4.0, an operating environment based on FreeBSD and Mach, supported by Aple Mac OS X, version 10.3, on a PowerPC processor
