background: I remotely support some Compaq deskpro computers with Red Hat Linux release 6.2 that have been in use for several years. They have Multitech hardware modems on ttyS1 for support and nightly updates, and a serial keypad device on ttys0 that is used for account lookup. Normally there isn't even a monitor attached to the system but for troubleshooting I can have one setup and talk them through some basic things I've learned.

reason for post: I'm having problems dialing in to one of the systems. Initially I dialed in, got connected to the modem but did not get a login. My helper at the other end says lights flickered for a while and then all of them went out except for one of the speed lights. When we checked /etc/inittab, ttyS1 was off. This was edited to read "respawn" and then we ran "init q". (No X-Windows by the way.) This did not bring up terminal ready (TR) on the modem so we rebooted. When the system came back up, TR was on and I tried to dial in again. Same thing; I got connected to the modem, lights flickered for a while then went out, and TR was gone.

actual question: Is there something in linux that could be turning off ttyS1? If there is, what can I do to make it stop?

What do you mean by "turning off ttyS1"? Is something in your inittab file changing? What are the permissions/ownership of /etc/inittab. Perhaps you could post the inittab file. If something is changing, perhaps a "before" and "after" version.

I don't want to get your hopes up; I am fishing at this point. From what I understand it does seem strange.

The /etc/inittab line for ttyS1 is changing from "respawn" to "off". I'm talking a user through vi to change it back to respawn and then having him reboot the system for it to take effect. ("init q" either didn't reexamine inittab or my Texas accent didn't translate in South Dakota.) As I can only access the system via dialup, I'm unable to take before and after pictures.

W/o more info, the only thing that comes to mind is perhaps that box is behaving weird because it has been compromised. I can't think of a reason why the system would automatically change the inittab file. You could try checking out the system with chkrootkit and rootkit hunter.

You haven't stated why you are using such an old system. You might want to consider taking this opportunity to update to something newer. (BTW, that far back, RH had terrible security policies out of the box. This was much improved by RH 8.0.)

Upgrade is cost prohibitive for this application and security is not so much an issue as access is by dialup only. The company that originally purchased these systems started out with about 30 locations and now only use 9 of them. Several of the remaining 21 have expired and the remainder were kept for replacements. The system with the problem was being tested for use as a replacment. As of today, it's a spare parts system.

Thanks for the replys.