TTY Autologin: Difference between revisions
mNo edit summary |
mNo edit summary |
||
| Line 32: | Line 32: | ||
As parameters are passed: | As parameters are passed: | ||
* '''-f''' flag which stands for "Do not authenticate (user already authenticated)" | * '''-f''' flag which stands for "Do not authenticate (user already authenticated)" | ||
* ''username'' in this example is ''root'' but if you created a new user, | * ''username'' in this example is ''root'' but if you created a new user, its username can be used instead. | ||
== Compiling the autologin.c program == | == Compiling the autologin.c program == | ||
| Line 47: | Line 47: | ||
{{Cmd|# vi /etc/inittab }} | {{Cmd|# vi /etc/inittab }} | ||
replace | replace "'':respawn:/sbin/getty''" with "'':respawn:/sbin/getty -n -l /usr/sbin/autologin''" for each TTY you want to enable autologin. | ||
* The getty's '''-n''' flag do not prompt the user for a login name | * The getty's '''-n''' flag do not prompt the user for a login name | ||
* The getty's '''-l''' flag invokes a custom login instead of /bin/login; in our case it is set to invoke /usr/sbin/autologin | * The getty's '''-l''' flag invokes a custom login instead of /bin/login; in our case it is set to invoke /usr/sbin/autologin | ||
==== Note ==== | ==== Note ==== | ||
To perform such replacement the following command can be used: | To perform such a replacement on all TTYs, the following command can be used: | ||
{{Cmd|# sed -i 's@:respawn:/sbin/getty@:respawn:/sbin/getty -n -l /usr/sbin/autologin@g' /etc/inittab }} | {{Cmd|# sed -i 's@:respawn:/sbin/getty@:respawn:/sbin/getty -n -l /usr/sbin/autologin@g' /etc/inittab }} | ||
* "'''@'''" is used as a delimiter | * "'''@'''" is used as a delimiter | ||
Revision as of 15:13, 11 September 2023
What follows is one from many different ways to get autologin.
How
- Writing a wrapper, called autologin, around /bin/login and moving it in /usr/sbin/
- Editing /etc/inittab specifying the use of /usr/sbin/autologin instead of /bin/login
Prerequisites
- A C compiler
- The musl-dev package which contains the C standard library
Example on how to assolve the prerequisites:
# apk add --repository https://dl-cdn.alpinelinux.org/alpine/edge/testing tcc # apk add musl-dev
Writing the autologin.c program
Create a file; in this example called autologin.c
# vi autologin.c
Write into it the following C program.
#include <unistd.h> int main() { execlp( "login", "login", "-f", "root", 0); }
The only thing it does is a system call to execute the login binary (part of busybox) which will be searched in PATH.
As parameters are passed:
- -f flag which stands for "Do not authenticate (user already authenticated)"
- username in this example is root but if you created a new user, its username can be used instead.
Compiling the autologin.c program
If using tcc:
# tcc -o autologin autologin.c
Move the binary autologin to /usr/sbin
# mv autologin /usr/sbin/
Editing /etc/inittab
Open /etc/inittab
# vi /etc/inittab
replace ":respawn:/sbin/getty" with ":respawn:/sbin/getty -n -l /usr/sbin/autologin" for each TTY you want to enable autologin.
- The getty's -n flag do not prompt the user for a login name
- The getty's -l flag invokes a custom login instead of /bin/login; in our case it is set to invoke /usr/sbin/autologin
Note
To perform such a replacement on all TTYs, the following command can be used:
# sed -i 's@:respawn:/sbin/getty@:respawn:/sbin/getty -n -l /usr/sbin/autologin@g' /etc/inittab
- "@" is used as a delimiter
- The -i flag edits the file in-place
Cleaning up
It is possible to remove the autologin.c file, the C compiler and the musl-dev package
# rm autologin.c # apk del tcc # apk del musl-dev