Mr. Suhas Ghosh wrote:
Hi, Thank you very much Joe and Florian for your response. Actually this is part of a Embedded system. So my total root file system will be in flash which is read only. So I can not make root read write. I have another RW root also. but there is no problem like Unable to change tty /dev/tty1 : Read Only file System.It is working fine. Now regarding Hard Disk error,this same system is running in 2 machines so I think this is not problem of Hard Disk. When I remounted this Read only root as RW using 'mount -o remount,rw /' and again try to login then no problem it is working fine.I have tried to change TTYGRP and TTYPERM in /etc/login.defs as login proces using these 2 variables. I want to know due to this error is there any harm or problem in console operation?Ok waiting for your kind response. Thanking you in advance. Suhas.
When a non-root user logs in, the login process must change the owner and possibly the permissions on the tty device being used (ttyX for the consoles, ttySX for serial devices, /dev/pts/X for pseudo terminals [where X is a number]). This is to allow the user to be able to control the read/write permissions on the device, usually with the 'mesg' command.
I have no way to test, but I assume that since the devices by default are owned by root, a root login would have no problems. However, a normal user login will not gain ownership of the device in question and so will not be able to set permissions on it. This means a non-privileged process won't be able to read or write the terminal device, if the default permissions of rw------- are set. And a regular user's shell is a non-privileged process.
You will need to fix this if you have a non-root login configured. The simplest way is to set the terminal permissions to be rw-rw-rw- when you create the device nodes. You will still get the error message but at least processes will be able to read/write the device.
More difficult to set up is the udev solution suggested by another poster, but this is probably a more robust solution, assuming you have enough RAM to build the tmpfs filesystems.
Bob
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