Sign up using Email and Password. PuTTY of any type of ssh session If I start up these services with a proper tty, they work and continue to run. There is no doubt that the addition of container technologies to Linux has created a lot of value, allowing workloads to be effectively and efficiently isolated from each other. Most interactive applications editors, mail user agents, shells, all programs relying on curses or readline run in raw mode, and handle all the line editing commands themselves. Thus it supports login sessions.

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Great and informative read indeed! I have been trying to chew through documents in every unix book possible to explain how the TTY system really works. If a process is sleeping, the WCHAN try “wait channel”, the name of the wait queue will tell you what kernel event the process is waiting for. Am I missing something here?


This is how I learned about things in the past, from people who knew their craft well. It seems like a reasonably clean, if slightly inelegant, solution.

Brilliant article, and now I know enough to stay the fuck away until I must. Pulling other threads of this story together, if you run xen-create-imageit will mount the devpts filesystem pssudo its chroot environment with no options. I don’t know if the -t there is really necessary, but maybe it is in your environment.


Containers, pseudo TTYs, and backward compatibility []

The history of pseudo TTYs contains the sort of mix of clever ideas and unfortunate choices that we’ve come to expect in fast-moving technology. Finally, stty -a lists a bunch of switches. Setuid programs are always a little bit risky — it is important that they cannot be tricked into doing the wrong thing, so they must be provided with complete information in ways that cannot easily be forged. Sort, OTOH, can call setsidbecuase it also leaves the process group: For example, when you ssh in to a machine and run lsthe ls command is sending its output to a pseudo-terminal, the other side of which is attached to the SSH daemon.

With this there is no need for a setuid helper program. I’ve been using Linux for 10 years, and this taught me quite a bit. That’s missing from your article. I really admire you!!

The TTY demystified

This code moves the cursor to the last line on the screen, by writing the corresponding control sequences to the TTY device. Thats an awesome link. This may allow you to tighten up the sudoers file a bit too. All mixed up in psedo bucket for monsieur. Don’t run stty 1 from, e.


The most recent patch makes the claim that:. Do we not need them anymore? Kernel provided pseudoserial port connected to programs emulating terminals, such as xterm, or screen. In April of that year, Linux 2. Needs to execute this to get the changed winsize in a new process since at least bash 2.

Anybody with access permissions to the TTY pseudk can change the interactive attention character and toggle this feature; additionally, the session manager keeps track of the TTY configuration of each job, and updates the TTY whenever there is a job switch.

Or all session members would have to lose access to the CTTY, just as if the session leader died.

By running ps lyou can see which processes are running, and which are sleeping. I am not responsible for what people other than myself write in the forums.

The Linux Console is not a physical terminal, yet it is connected to a ttyN not to a ptyN. First teletype linuz made in Germany around the 30s or 40s. IF it has ctty