For what it is worth, I do have the 50-udev.permissions line as suggested by the other SL response. I had checked this yesterday before sending email to SL group although I did not report it. ttyS*:root:uucp:0660 ON SL4.4 powering on the serial device will switch from root:uucp 0660 to root:root 0620 sudo chown root:uucp /dev/ttyS0 works to switch owner to root:uucp sudo chmod 0660 /dev/ttyS0 will switch group back to root running c code switches group back to root I'm not a system admin, all I know, is that I can follow the web comments about adding a user to group uucp and get SL5.0 to work with my serial device and associated c code in a consistent way. The laptop with SL4.4 doesn't play the same way. SL4.4 was installed from CD but not updated in any way. Bill Lutter ----- Original Message ----- From: Steven Timm <[log in to unmask]> Date: Tuesday, November 3, 2009 10:09 pm Subject: Re: serial ports and SL4.4 To: WILLIAM J LUTTER <[log in to unmask]> Cc: "[log in to unmask]" <[log in to unmask]> > I have SLF4.7 on my laptop and I don't have the problem you mention. > In the days when I had 4.4 it was OK too. > > Steve > > > On Tue, 3 Nov 2009, WILLIAM J LUTTER wrote: > > >If I install SL4.4 on a laptop and then try to use the /dev/ttyS0 > serial port, I find I can't control the ownership and permissions of > the port. It resets from 0660 root uucp to root root and owner rw > permissions. So, I can't add a user to the uucp group to manage usage > of the serial port (this works ok on SL5.0. If I try to just run > everything via sudo, it seems my terminal settings via stty have changed. > > > >I know I'm not using an up-to-date SL release, nevertheless, is this > a "known" issue with an obvious work around - so I don't have to reinstall? > > > >Bill Lutter > > > > -- > ------------------------------------------------------------------ > Steven C. Timm, Ph.D (630) 840-8525 > [log in to unmask] http://home.fnal.gov/~timm/ > Fermilab Computing Division, Scientific Computing Facilities, > Grid Facilities Department, FermiGrid Services Group, Assistant Group > Leader.