Posts Tagged ‘getty’

Set all logs to log to to physical console /dev/tty12 (tty12) on Linux

Wednesday, August 12th, 2020

tty linux-logo how to log everything to last console terminal tty12

Those who administer servers from the days of birth of Linux and who used actively GNU / Linux over the years or any other UNIX knows how practical could be to configure logging of all running services / kernel messages / errors and warnings on a physical console.

Traditionally from the days I was learning Linux basics I was shown how to do this on an old Debian Sarge 3.0 Linux without systemd and on all Linux distributions Redhat 9.0 / Calderas and Mandrakes I've used either as a home systems or for servers. I've always configured output of all messages to go to the last easy to access console /dev/tty12 (for those who never use it console switching under Linux plain text console mode is done with key combination of CTRL + ALT + F1 .. F12.

In recent times however with the introduction of systemd pretty much things changed as messages to console are not handled by /etc/inittab which was used to add and refresh physical consoles tty1, tty2 … tty7 (the default added one on Linux were usually 7), but I had to manually include more respawn lines for each console in /etc/inittab.
Nowadays as of year 2020 Linux distros /etc/inittab is no longer there being obsoleted and console print out of INPUT / OUTPUT messages are handled by systemd.
 

1. Enable Physical TTYs from TTY8 till TTY12 etc.


The number of default consoles existing in most Linux distributions I've seen is still from tty1 to tty7. Hence to add more tty consoles and be ready to be able to switch out  not only towards tty7 but towards tty12 once you're connected to the server via a remote ILO (Integrated Lights Out) / IdRAC (Dell Remote Access Controller) / IPMI / IMM (Imtegrated Management Module), you have to do it by telling systemd issuing below systemctl commands:
 

 

 # systemctl enable getty@tty8.service Created symlink /etc/systemd/system/getty.target.wants/getty@tty8.service -> /lib/systemd/system/getty@.service.

systemctl enable getty@tty9.service

Created symlink /etc/systemd/system/getty.target.wants/getty@tty9.service -> /lib/systemd/system/getty@.service.

systemctl enable getty@tty10.service

Created symlink /etc/systemd/system/getty.target.wants/getty@tty10.service -> /lib/systemd/system/getty@.service.

systemctl enable getty@tty11.service

Created symlink /etc/systemd/system/getty.target.wants/getty@tty11.service -> /lib/systemd/system/getty@.service.

systemctl enable getty@tty12.service

Created symlink /etc/systemd/system/getty.target.wants/getty@tty12.service -> /lib/systemd/system/getty@.service.


Once the TTYS tty7 to tty12 are enabled you will be able to switch to this consoles either if you have a physical LCD / CRT monitor or KVM switch connected to the machine mounted on the Rack shelf once you're in the Data Center or will be able to see it once connected remotely via the Management IP Interface (ILO) remote console.
 

2. Taking screenshot of the physical console TTY with fbcat


For example below is a screenshot of the 10th enabled tty10:

tty10-linux-screenshot-fbcat-how-to-screenshot-console

As you can in the screenshot I've used the nice tool fbcat that can be used to make a screenshot of remote console. This is very useful especially if remote access via a SSH client such as PuTTY / MobaXterm is not there but you have only a physical attached monitor access on a DCs that are under a heavy firewall that is preventing anyone to get to the system remotely. For example screenshotting the physical console in case if there is a major hardware failure occurs and you need to dump a hardware error message to a flash drive that will be used to later be handled to technicians to analyize it and exchange the broken server hardware part.

Screenshots of the CLI with fbcat is possible across most Linux distributions where as usual.

In Debian you have to first instal the tool via :
 

# apt install –yes fbcat


and on RedHats / CentOS / Fedoras

# yum install -y fbcat


Taking screenshot once tool is on the server of whatever you have printed on console is as easy as

# fbcat > tty_name.ppm


Note that you might want to convert the .ppm created picture to png with any converter such as imagemagick's convert command or if you have a GUI perhaps with GNU Image Manipulation Tool (GIMP).

3. Enabling every rsyslog handled message to log to Physical TTY12


To make everything such as errors, notices, debug, warning messages  become instantly logging towards above added new /dev/tty12.

Open /etc/rsyslog.conf and to the end of the file append below line :
 

daemon,mail.*;\
   news.=crit;news.=err;news.=notice;\
   *.=debug;*.=info;\
   *.=notice;*.=warn   /dev/tty12


To make rsyslog load its new config restart it:

 

# systemctl status rsyslog

 

 

 

rsyslog.service – System Logging Service
   Loaded: loaded (/lib/systemd/system/rsyslog.service; enabled; vendor preset: enabled)
   Active: active (running) since Mon 2020-08-10 04:09:36 EEST; 2 days ago
     Docs: man:rsyslogd(8)
           https://www.rsyslog.com/doc/
 Main PID: 671 (rsyslogd)
    Tasks: 4 (limit: 4915)
   Memory: 12.5M
   CGroup: /system.slice/rsyslog.service
           └─671 /usr/sbin/rsyslogd -n -iNONE

 

авг 12 00:00:05 pcfreak rsyslogd[671]:  [origin software="rsyslogd" swVersion="8.1901.0" x-pid="671" x-info="https://www.rsyslo
Warning: Journal has been rotated since unit was started. Log output is incomplete or unavailable.

 

systemctl restart rsyslog


That's all folks navigate by pressing simultaneously CTRL + ALT + F12 to get to TTY12 or use ALT + LEFT / ALT + RIGHT ARROW (console switch commands) till you get to the console where everything should be now logged.

Enjoy and if you like this article share to tell your sysadmin friends about this nice hack  ! 🙂

 

 

 

How to make screenshot in /dev/tty console on GNU / Linux – Taking picture JPEG / PNG snapshot of text console in systems without graphical environment

Monday, April 30th, 2012

I'm used to making picture screenshots in GNOME desktop environment. As I've said in my prior posts, I'm starting to return to my old habits of using console ttys for regular daily jobs in order to increase my work efficiency. In that manner of thoughts sometimes I need to take a screenshot of what I'm seeing in my physical (TTY consoles) to be able to later reuse this. I did some experimenting and this is how this article got born.

In this post, I will shortly explain how a picture of a command running in console or terminal in GNU / Linux can be made

Before proceeding to the core of the article, I will say few words on ttys as I believe they might be helpful someone.
The abbreviation of tty comes after TeleTYpewritter phrase and is dating back somewhere near the 1960s. The TTY was invented to help people with impaired eyesight or hearing to use a telephone like typing interface.

In Unix / Linux / BSD ttys are the physical consoles, where one logs in (typing in his user/password). There are physical ttys and virtual vtys in today *nixes. Today ttys, are used everywhere in a modern Unixes or Unix like operating system with or without graphical environments.
Various Linux distributions have different number of physical consoles (TTYs) (terminals connected to standard output) and this depends mostly on the distro major contributors, developers or surrounding OS community philosophy.
Most modern Linux distributions have at least 5 to 7 physical ttys. Some Linux distributions like Debian for instance as of time of writting this, had 7 active by default physical consoles.
Adding 3 more ttys in Debian / Ubuntu Linux is done by adding the following lines in /etc/inittab:
 

7:23:respawn:/sbin/getty 38400 tty7
8:23:respawn:/sbin/getty 38400 tty8
9:23:respawn:/sbin/getty 38400 tty9

On some Linux distributions like Fedora version 9 and newer ones, new ttys can no longer be added via /etc/inittab,as the RedHat guys changed it for some weird reason, but I guess this is too broad issue to discuss ….

In graphical environments ttys are called methaphorically "virtual". For instance in gnome-terminal or while connecting to a remote SSH server, a common tty naming would be /dev/pts/8 etc.

tty command in Linux and BSDs can be used to learn which tty, one is operating in.

Here is output from my tty command, issued on 3rd TTY (ALT+F3) on my notebook:
 

noah:~# tty
/dev/tty3

A tty cmd output from mlterm GUI terminal is like so:
 

hipo@noah:~$ tty/dev/pts/9

Now as mentioned few basic things on ttys I will proceed further to explain how I managed to:

a) Take screenshot of a plain text tty screen into .txt file format
b) take a (picture) JPG / PNG screenshot of my Linux TTY consoles content

1. Take screenshot of plain text tty screen into a plain (ASCII) .txt file:

To take a screenshot of tty1, tty2 and tty3 text consoles in a txt plain text format, cat + a standard UNIX redirect is all necessery:
 

noah:~# cat /dev/vcs1 > /home/hipo/tty1_text_screenshot.txt
noah:~# cat /dev/vcs2 > /home/hipo/tty2_text_screenshot.txt
noah:~# cat /dev/vcs3 > /home/hipo/tty3_text_screenshot.txt

This will dump the text content of the console into the respective files, if however you try to dump an ncurses library like text interactive interfaces you will end up with a bunch of unreadable mess.
In order to read the produced text 'shots' onwards less command can be used …
 

noah:~# less /home/hipo/tty1_text_screenshot.txt
noah:~# less /home/hipo/tty2_text_screenshot.txt
noah:~# less /home/hipo/tty3_text_screenshot.txt

2. Take picture JPG / PNG snapshot of Linux TTY console content

To take a screenshot of my notebook tty consoles I had to first install a "third party program" snapscreenshot . There is no deb / rpm package available as of time of writting this post for the 4 major desktop linux distributions Ubuntu, Debian, Fedora and Slackware.
Hence to install snapscreenshot,I had to manually download the latest program tar ball source and compile e.g.:
 

noah:~# cd /usr/local/src
noah:/usr/local/src# wget -q http://bisqwit.iki.fi/src/arch/snapscreenshot-1.0.14.3.tar.bz2
noah:/usr/local/src# tar -jxvvvf snapscreenshot-1.0.14.3.tar.bz2

noah:/usr/local/src# cd snapscreenshot-1.0.14.3
noah:/usr/local/src/snapscreenshot-1.0.14# ./configure && make && make install
Configuring…
Fine. Done. make.
make: Nothing to be done for `all'.
if [ ! "/usr/local/bin" = "" ]; then mkdir –parents /usr/local/bin 2>/dev/null; mkdir /usr/local/bin 2>/dev/null; \
for s in snapscreenshot ""; do if [ ! "$s" = "" ]; then \
install -c -s -o bin -g bin -m 755 "$s" /usr/local/bin/"$s";fi;\
done; \
fi; \
if [ ! "/usr/local/man" = "" ]; then mkdir –parents /usr/local/man 2>/dev/null; mkdir /usr/local/man 2>/dev/null; \
for s in snapscreenshot.1 ""; do if [ ! "$s" = "" ]; then \
install -m 644 "$s" /usr/local/man/man"`echo "$s"|sed 's/.*\.//'`"/"$s";fi;\
done; \
fi

By default snapscreenshot command is made to take screenshot in a tga image format, this format is readable by most picture viewing programs available today, however it is not too common and not so standartized for the web as the JPEG and PNG.
Therefore to make the text console tty snapshot taken in PNG or JPEG one needs to use ImageMagick's convert tool. The convert example is also shown in snapscreenshot manual page Example section.

To take a .png image format screenshot of lets say Midnight Commander interactive console file manager running in console tty1, I used the command:
 

noah:/home/hipo# snapscreenshot -c1 -x1 > ~/console-screenshot.tga && convert ~/console-screenshot.tga console-screenshot.png

Linux text console tty mc screenshot with snapscreenshot terminal / console snapshotting program

Note that you need to have read/write permissions to the /dev/vcs* otherwise the snapscreenshot will be unable to read the tty and produce an error:
 

hipo@noah:~/Desktop$ snapscreenshot -c2 -x1 > snap.tga && convert snap.tga snap.pngGeometry will be: 1x2Reading font…/dev/console: Permission denied

To take simultaneous picture screenshot of everything contained in all text consoles, ranging from tty1 to tty5, issue:
 

noah:/home/hipo# snapscreenshot -c5 -x1 > ~/console-screenshot.tga && convert ~/console-screenshot.tga console-screenshot.png

Here is a resized 480×320 pixels version of the original screenshot the command produces:

All text Consoles tty1 to tty5 merged screenshot png image with snapscreenshot taken on Debian GNU / Linux

Storing a picture shot of the text (console) screen in JPEG (JPG) format is done analogously just the convert command output extension has to be changed to jpeg i.e.:
 

noah:/home/hipo# snapscreenshot -c5 -x1 > ~/console-screenshot.tga && convert ~/console-screenshot.tga console-screenshot.jpeg

I've also written a tiny wrapper shell script, to facilitate myself picture picture taking as I didn't like to type each time I want to take a screenshot of a tty the above long line.

Here is the wrapper script I wrote:
 

#!/bin/sh
### Config
# .tga produced file name
output_f_name='console-screenshot.tga';
# gets current date
cur_date=$(date +%d_%m_%Y|sed -e 's/^ *//');
# png output f name
png_f_name="console-screenshot-$cur_date.png";
### END Config
snapscreenshot -c$arg1 -x1 > $output_f_name && convert $output_f_name $png_f_name;
echo "Output png screenshot from tty1 console produced in";
echo "$PWD/$png_f_name";
/bin/rm -f $output_f_name;

You can also download my console-screenshot.sh snapscreenshot wrapper script here

The script is quite simplistic to use, it takes just one argument which is the number of the tty you would like to screenshot.
To use my script download it in /usr/local/bin and set it executable flag:
 

noah:~# cd /usr/local/bin
noah:/usr/local/bin# wget -q https://pc-freak.net/~bshscr/console-screenshot.sh
noah:/usr/local/bin# chmod +x console-screenshot.sh

Onwards to use the script to snapshot console terminal (tty1) type:
 

noan:~# console-screenshot.sh

I've made also mirror of latest version of snapscreenshot-1.0.14.3.tar.bz2 here just in case this nice little program disappears from the net in future times.