Broader context, I'm using QEMU+KVM to virtualize an ubuntu machine like this:

qemu-system-x86_64 \
    -enable-kvm \
    -m 2048 \
    -nic none \
    -vnc :5 \
    -hda test-vm.raw \
    -device vfio-pci,host=01:00.0 \
    -serial unix:/tmp/console.sock,server,nowait

I'm using /tmp/console.sock to login into the virtual machine via "serial": socat stdin,raw,echo=0,escape=0x11 "unix-connect:/tmp/console.sock" This works without any major problems. However, when I'm entering sudo su the prompt for the password appears on the terminal that has started the agetty process (not the serial console). I know that starting agetty from a terminal isn't how you would start it normally. However, I'm very curious as to how this happens and how I can start agetty from the terminal without it having _any_ connection (sudo asking for the password on the terminal that has started agetty leads me to believe that there _is_ some connection) to the terminal that has started it. I already tried:

$ nohup agetty ttyS0 9600 &
$ disown

Without success. Would love to know the underlying mechanic that is at play here and how I can possibly remedy the issue*. *As said, I know that starting agetty from a normal terminal isn't how you would use the program. I'm still interested in how this happens and how you could prevent agetty from acting this way.

I am trying to set up an alpine linux machine that needs to run an user program at the startup. I did not add any user except for root. After searching for solution of how to enable automatic login i have found instructions that said i need to use agetty. In order: 1. apk add util-linux to add agetty. 2. cd /etc/init.d && ln -s agetty agetty.tty1 to add agetty service for the terminal. 3. cd /etc/conf.d && cp agetty agetty.tty1 to add configuration. 4. nano agetty.tty1 or use other editor to add "--autologin $USER --noclear" to agetty options 5. rc-update add agetty.tty1 to ensure launch at start. One thing that bothered me was the fact instruction told about turning off previous agetty service before adding new, changed one - and there was no agetty service enabled. However, things went wrong: during machine start i could see output of the automatic login before several services (chrony and some other) were started, and then i got another login prompt that did not work anymore. it seemed as there were bno two logins/terminals and system became unworkable. What was my error and how can i fix this?

My apologies if this is a ultra basic question: Does linux / systemd / agetty support double ended serial-getty consoles? For example I have two remote servers A and B, they are running a recent ubuntu with systemd, agetty and screen installed. There is a null modem cable installed bewteen the servers and it appears on /dev/ttyS0 on both. From Server B I can use screen to get a login prompt (agetty) on server A. From that prompt I can reboot the server A, grub comes up I can make choices in grub, boot Linux, I see the boot messages, then a successful login prompt etc all over a serial link from B. Is it possible to do the reverse with the same serial port/link ? Can I use screen to login to server B from A over the same /dev/ttyS0? Can server B also have agetty listen on /dev/ttyS0 when it is not in use by screen? And if not and I need a second serial port/cable to get from A -> B, is that a hardware limitation of UART or a software limitation of agetty or systemd ? And if its a systemd issue it this possible in a non-systemd Linux say Gentoo? Thank you in advance.

I am trying to read source code to understand which process is reponsible for these mapping, but I can't still figure it out. Can anyone give me a hint about which code is relative to it ? source code: agetty+login(util-linux project) , systemd

Recently, I noticed that when using tty to login to my computer, there was a delay (around 20 seconds) between the time I enter my username and the time I'm getting asked for my password. Where can it come from ? I don't have such delay when using su username or ssh username@localhost and my password is asked right away. I'm using Arch Linux with kernel 5.14.16. **EDIT** Finally found the problem. There was a broken module in PAM (fingerprint auth) which needed to timeout before asking a password. Just disabled the module.

For the sake of learning, I wanted to start a new terminal (let's say tty10) from the command prompt. I know I can just run sudo systemctl start getty@tty10.service, but I want to run it manually for now. I checked systemd service getty@ and it uses the following command line: /sbin/agetty -o '-p -- \\u' --noclear %I $TERM So, trying to replicate that from a terminal (tty1) I ran this: sudo /sbin/agetty -o '-p -- ' --noclear tty10 linux It indeed started a new login prompt at terminal 10, I enter the username but it never prompts for a password. Besides, when I go back to terminal 1 I see it logged out. What am I doing wrong?

I am building a dumb terminal with an arduino and I can now see the output of serial connections. How do I get a login/shell? I have tried screen /dev/ttyACM0 and that lets me type on the host computer and see the results on the terminal screen, but no shell. Using screen's :exec /bin/sh command starts a shell on that controlling xterm window but no longer outputs to the serial line. various attempts with agetty -L /dev/ttyACM0 9600 just sit and hang for a minute then exits without ever having put anything on the screen. I have tried cu -l /dev/ttyACM0 -s 9600 and again it hangs with no screen interaction. I have connected minicom to echo keys onto the arduino similar to screen but could not figure out how to get a shell. To be clear I am trying to access my main computer via the arduino based terminal, and I can not find a way to make my main computer offer a shell session to the arduino over a USB serial connection.

All, I want to setup "Kiosk" mode on a real terminal with systemd. My initial approach was setup autologin with systemd and run the application from .bashrc. However the user is able to breakout to shell in this approach. What I would like to achieve is at bootup, the application auto-launches and if it crashes respawns again. Any suggestion or pointers would be helpful.

I've a cloud server, with CentOS distribution, and an Apache instance to manage some web apps, like Wordpress or PrestaShop. I noticed that an error is reported in log files (var/log/). * In particular in messages:

May 30 11:54:41 xxx00962 systemd: Starting Serial Getty on ttyS0...
     May 30 11:54:41 xxx00962 systemd: Started Serial Getty on ttyS0.
     May 30 11:54:51 xxx00962 systemd: serial-getty@ttyS0.service holdoff time over, scheduling restart.
     May 30 11:54:51 xxx00962 systemd: Stopping Serial Getty on ttyS0...

* and in secure:

May 30 15:51:30 xxx00962 agetty: /dev/ttyS0: not a character device

where xxx00962 is the (anonymized) hostname. I don't know what is getty for, but I'd like to solve the problem. Someone can help me and explain how getty works?

I'm trying to setup a 80's service with Mystic BBS (that runs on telnet), including a dial-up access with a U.S. Robotics modem connected to the serial port of the server. I succeeded with mgetty: /sbin/mgetty -D -a -x6 /dev/ttyUSB0 This brings the Ubuntu login on the remote client, that I can replace with the output of telnet on localhost, configuring the process that is started upon the connection is established. **The problem is that mgetty requires the caller to enter an existing username on the server** before he can get to the welcome screen of Mystic. So, I switched to agetty: it has an auto-login feature that will skip the first step and it will directly bring the user to the telnet session using a conventional non-admin linux user. Then the user will login or register to the BBS service. Unfortunately, I can't get it to work: agetty -I 'ATE0Q1&D2&C1S0=1\015' ttyUSB0 vt100 With this command I can connect from the client, but nothing is shown on the terminal. The connection is stable, but nothing seems to be transmitted. If I send some strokes from the terminal and I monitor /dev/ttyUSB0 with *screen* on the server, I can see garbage characters that arrives, but everything is scrambled. Same thing if I send strokes from the *screen* session on the server, some "brick" characters are shown on the client terminal.

I'm running a ubuntu server installation with a tty console, and sshd terminal logins. Both ssh keys and passwords work for authenticating over sshd. Lately, on the console, when I try to log in in text mode, I get a curious behavior: I enter my login name. It prompts for the password. However, it very quickly prints a newline, and whatever part of the password I hadn't typed already is echoed in cleartext to the console. Then, it prompts for login:, but quickly times out and prompts for login: again ... 5 times, until it goes back to clear the screen, and re-issue the agetty process. At that point it's "stable" and waits for a username again, but entering a username and pressing enter re-starts the "timeout and newline" behavior. The systemd log for getty@tty1 says the following: -- Unit getty@tty1.service has finished starting up. -- -- The start-up result is RESULT. Feb 08 12:12:47 xps15 login: pam_unix(login:auth): conversation failed Feb 08 12:12:47 xps15 login: pam_unix(login:auth): auth could not identify password for [jwatte] Feb 08 12:12:50 xps15 login: FAILED LOGIN (1) on '/dev/tty1' FOR 'jwatte', Authentication failure Feb 08 12:12:51 xps15 login: pam_securetty(login:auth): cannot determine username Feb 08 12:12:54 xps15 login: FAILED LOGIN (2) on '/dev/tty1' FOR 'UNKNOWN', Error in service module Feb 08 12:12:55 xps15 login: pam_securetty(login:auth): cannot determine username Feb 08 12:12:58 xps15 login: FAILED LOGIN (3) on '/dev/tty1' FOR 'UNKNOWN', Error in service module Feb 08 12:12:59 xps15 login: pam_securetty(login:auth): cannot determine username Feb 08 12:13:03 xps15 login: FAILED LOGIN (4) on '/dev/tty1' FOR 'UNKNOWN', Error in service module Feb 08 12:13:03 xps15 login: pam_securetty(login:auth): cannot determine username Feb 08 12:13:06 xps15 login: FAILED LOGIN (5) on '/dev/tty1' FOR 'UNKNOWN', Error in service module Feb 08 12:13:06 xps15 login: TOO MANY LOGIN TRIES (5) on '/dev/tty1' FOR 'UNKNOWN' Feb 08 12:13:06 xps15 login: pam_mail(login:session): cannot determine username Feb 08 12:13:06 xps15 login: pam_unix(login:session): close_session - error recovering username Feb 08 12:13:06 xps15 systemd: getty@tty1.service: Service has no hold-off time, scheduling restart. Feb 08 12:13:06 xps15 systemd: getty@tty1.service: Scheduled restart job, restart counter is at 1. -- Subject: Automatic restarting of a unit has been scheduled -- Defined-By: systemd -- Support: http://www.ubuntu.com/support -- -- Automatic restarting of the unit getty@tty1.service has been scheduled, as the result for -- the configured Restart= setting for the unit. I imagine the problem is the first two lines: pam_unix(login:auth): conversation failed pam_unix(login:auth): auth could not identify password for [jwatte] Why would this happen, and how can I best debug it?

after starting agetty on my Raspberry Pi in order to attach a VT420 terminal to it, I still have an issue: The shell language must be set to en_US and exported by hand right after logging in on the terminal (my version of Raspbian has German locale). Motivation: The terminal does not support UTF-8 characters (and sometimes even stops working when receiving such a character), so I decided to fall back to English locale especially when logging in on the terminal. In all other cases (SSH etc.), UTF-8 is absolutely fine. I followed the suggestion set forth in question #455261 and added the following line to the systemd service file responsible for agetty: Environment="LANG=en_US" After a daemon reload and a restart of agetty, the login prompt is now in English, but when I start a program (say, df -h), its output is still in German and contains UTF-8 characters, causing the already-mentioned problems: pi@autoradio:/import/valen/autoradio $ df -h Dateisystem Grö …whereas the ö sequence should read as "ö". On the shell, I would say, export LANG=en_US, but I am not sure about how to export an env variable set in a systemd config. Does anybody know that? Thank you.

I'm trying to get a login prompt on an embedded system using Debian and systemd. The system is connected via a physical serial console to a host PC. If I start the kernel with the cmdline parameters console=ttyS5,115200 console=tty1 systemd.journald.forward_to_console=1 I do see all the kernel messages from /dev/kmsg and systemd logs, but I never see a login prompt. If I omit console=tty1 the kernel log is still beeing printed, but the systemd logs appear with a 30 seconds timeout for each line. What's the problem here? The same root file system works just fine for a similar embedded system.

In my QEMU virtual machine (started with qemu-kvm -boot d arch-freebsd.img -m 4096) I'd like to access an agetty terminal, which I'd normally access with Ctrl+Alt+F2 (or F3 if I need tty3, F4 if tty4, *etc.*), unfortunately pressing these keys just merely changes me to an agetty terminal on my host (as opposed to the guest system I'm trying to go to tty2 in). If this were a VirtualBox VM I'd press Ctrl+F2 (specifically the Ctrl in the centre of my keyboard, i.e. my right Ctrl key) to access tty2, but this doesn't work with QEMU. If you suggest I press Ctrl+Alt+G to get the VM to grab all my keyboard and mouse inputs, then pressing the keys to access the agetty terminals I've tried doing that and it doesn't work. EDIT: The proposed duplicate link doesn't list what solved my problem, pressing Alt+Fx. I've tried Ctrl+Alt+Fx that seems to be suggested there (although I'm having trouble getting my head around what it's about as what VNC is, is a mystery to me), that's kind of the problem here.