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[[Category:Boot process]] | [[Category:Boot process]] | ||
[[Category:Linux console]] | [[Category:Linux console]] | ||
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[[ja:Getty]] | [[ja:Getty]] | ||
[[pt:Getty]] | |||
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[[zh-hans:Getty]] | [[zh-hans:Getty]] | ||
{{Related articles start}} | {{Related articles start}} | ||
{{Related|Display manager}} | {{Related|Display manager}} | ||
{{Related articles end}} | {{Related articles end}} | ||
A [[w:getty (Unix)|getty]] is the generic name for a program which manages a terminal line and its connected terminal. Its purpose is to protect the system from unauthorized access. Generally, each getty process is started by [[systemd]] and manages a single terminal line. | A [[w:getty (Unix)|getty]] is the generic name for a program which manages a terminal line and its connected terminal. Its purpose is to protect the system from unauthorized access. Generally, each getty process is started by [[systemd]] and manages a single terminal line. | ||
== Installation == | == Installation == | ||
''agetty'' is the default getty in Arch Linux, as part of the {{Pkg|util-linux}} package. | |||
''agetty'' is the default getty in Arch Linux, as part of the {{Pkg|util-linux}} package | |||
Alternatives include: | Alternatives include: | ||
* {{App|mingetty|A minimal getty which allows automatic logins.|{{AUR|mingetty}}|{{AUR|mingetty}}}} | * {{App|mingetty|A minimal getty which allows automatic logins.|{{AUR|mingetty}}|{{AUR|mingetty}}}} | ||
* {{App|mgetty|A versatile program to handle all aspects of a modem under Unix.|http://mgetty.greenie.net/|{{AUR|mgetty}}}} | * {{App|mgetty|A versatile program to handle all aspects of a modem under Unix.|http://mgetty.greenie.net/|{{AUR|mgetty}}}} | ||
== | == Tips and tricks == | ||
=== Staircase effect === | |||
''agetty'' modifies the TTY settings while waiting for a login so that the newlines are not translated to CR-LFs. This tends to cause a "staircase effect" for messages printed to the console. | |||
It is entirely harmless, but in the event it persists once logged, you can fix this behavior with: | |||
$ stty onlcr | |||
See this [https://bbs.archlinux.org/viewtopic.php?id=264094 forums discussion] on the subject. | |||
=== Add additional virtual consoles === | |||
Agetty manages virtual consoles and six of these virtual consoles are provided by default in Arch Linux. They are usually accessible by pressing {{ic|Ctrl+Alt+F1}} through {{ic|Ctrl+Alt+F6}}. | |||
Configuration relies on systemd [[ | Open the file {{ic|/etc/systemd/logind.conf}} and set the option {{ic|1=NAutoVTs=6}} to the number of virtual terminals that you want at boot. | ||
If needed, it is possible to temporarily [[start]] a {{ic|getty@tty''N''.service}} service directly. | |||
=== Automatic login to virtual console === | |||
Configuration relies on systemd unit [[drop-in file]]s to override the default parameters passed to ''agetty''. | |||
Configuration differs for virtual versus serial consoles. In most cases, you want to set up automatic login on a virtual console, (whose device name is {{ic|tty''N''}}, where {{ic|''N''}} is a number). The configuration of automatic login for serial consoles will be slightly different. Device names of the serial consoles look like {{ic|ttyS''N''}}, where {{ic|''N''}} is a number. | Configuration differs for virtual versus serial consoles. In most cases, you want to set up automatic login on a virtual console, (whose device name is {{ic|tty''N''}}, where {{ic|''N''}} is a number). The configuration of automatic login for serial consoles will be slightly different. Device names of the serial consoles look like {{ic|ttyS''N''}}, where {{ic|''N''}} is a number. | ||
{{Tip|Consider using [[greetd]]'s auto-login feature. It will not auto-login a second time if the initial session exits, but will show a login screen instead.}} | |||
==== Virtual console ==== | |||
[[ | Create a [[drop-in file]] for {{ic|getty@tty1.service}} with the following contents: | ||
{{hc|/etc/systemd/system/getty@tty1.service.d/ | {{hc|/etc/systemd/system/getty@tty1.service.d/autologin.conf|2= | ||
[Service] | [Service] | ||
ExecStart= | ExecStart= | ||
ExecStart=-/ | ExecStart=-/sbin/agetty -o '-p -f -- \\u' --noclear --autologin ''username'' %I $TERM | ||
}} | }} | ||
{{Tip|The option {{ic|1=Type=idle}} found in the default {{ic|getty@.service}} will delay the service startup until all jobs (state change requests to units) are completed in order to avoid polluting the login prompt with boot-up messages. When [[Start X at login|starting X automatically]], it may be useful to start {{ic|getty@tty1.service}} immediately by adding {{ic|1=Type=simple}} into the | {{Tip| | ||
* The option {{ic|1=Type=idle}} found in the default {{ic|getty@.service}} will delay the service startup until all jobs (state change requests to units) are completed in order to avoid polluting the login prompt with boot-up messages. When [[Start X at login|starting X automatically]], it may be useful to start {{ic|getty@tty1.service}} immediately by adding {{ic|1=Type=simple}} into the drop-in file. Both the init system and ''startx'' can be [[Silent boot|silenced]] to avoid the interleaving of their messages during boot-up. | |||
* See [[Silent boot#agetty]] for an example virtual console drop-in file which hides the login prompt completely. | |||
* The above snippet will cause the loginctl session type to be set to {{ic|tty}}. If desirable (for example if [[Start X at login|starting X automatically]]), it is possible to manually set the session type to {{ic|wayland}} or {{ic|x11}} by adding {{ic|1=Environment=XDG_SESSION_TYPE=x11}} or {{ic|1=Environment=XDG_SESSION_TYPE=wayland}} into this file. | |||
}} | |||
If you want to | If you do not want full automatic login, but also do not want to type your username, see [[#Prompt only the password for a default user in virtual console login]]. | ||
If you want to use a ''tty'' other than ''tty1'', see [[systemd/FAQ#How do I change the default number of gettys?]]. | |||
Create | ==== Serial console ==== | ||
Create a [[drop-in file]]: | |||
{{hc|/etc/systemd/system/serial-getty@ttyS0.service.d/autologin.conf|2= | {{hc|/etc/systemd/system/serial-getty@ttyS0.service.d/autologin.conf|2= | ||
[Service] | [Service] | ||
ExecStart= | ExecStart= | ||
ExecStart=-/ | ExecStart=-/sbin/agetty -o '-p -f -- \\u' --keep-baud --autologin ''username'' 115200,57600,38400,9600 - $TERM | ||
}} | |||
==== Nspawn console ==== | |||
To configure auto-login for a [[systemd-nspawn]] container, override {{ic|console-getty.service}} by creating a [[drop-in file]]: | |||
{{hc|/etc/systemd/system/console-getty.service.d/autologin.conf|2= | |||
[Service] | |||
ExecStart= | |||
ExecStart=-/sbin/agetty -o '-p -f -- \\u' --noclear --keep-baud --autologin ''username'' - 115200,38400,9600 $TERM | |||
}} | }} | ||
If {{ic|machinectl login ''my-container''}} method is used to access the container, also adjust the {{ic|container-getty@.service}} template that manages {{ic|pts/[0-9]}} pseudo ttys: | |||
{{hc|/etc/systemd/system/container-getty@.service.d/autologin.conf|2= | |||
[Service] | |||
ExecStart= | |||
ExecStart=-/sbin/agetty -o '-p -f -- \\u' --noclear --keep-baud --autologin ''username'' - 115200,38400,9600 $TERM | |||
}} | |||
{{hc|/etc/systemd/system/ | === Prompt only the password for a default user in virtual console login === | ||
Getty can be used to login from a virtual console with a default user, typing the password but without needing to insert the username. For instance, to prompt the password for {{ic|''username''}} on {{ic|tty1}}: | |||
{{hc|/etc/systemd/system/getty@tty1.service.d/skip-username.conf|2= | |||
[Service] | [Service] | ||
ExecStart= | ExecStart= | ||
ExecStart=-/sbin/agetty -- | ExecStart=-/sbin/agetty -o '-p -- ''username''<nowiki/>' --noclear --skip-login - $TERM | ||
}} | }} | ||
and then [[enable]] {{ic|getty@tty1}}. | |||
By default, Arch has the {{ic|getty@tty1}} service enabled. The service file already passes {{ic|--noclear}}, which stops agetty from clearing the screen. However [[systemd]] clears the screen before starting it. To disable this behavior, create | === Have boot messages stay on tty1 === | ||
By default, Arch has the {{ic|getty@tty1}} service enabled. The service file already passes {{ic|--noclear}}, which stops agetty from clearing the screen. However [[systemd]] clears the screen before starting it. To disable this behavior, create a [[drop-in file]]: | |||
{{hc|1=/etc/systemd/system/getty@tty1.service.d/noclear.conf|2= | {{hc|1=/etc/systemd/system/getty@tty1.service.d/noclear.conf|2= | ||
Line 79: | Line 118: | ||
TTYVTDisallocate=no | TTYVTDisallocate=no | ||
}} | }} | ||
{{Note| | {{Note| | ||
* Make sure to remove {{ic|quiet}} from the [[kernel parameter]]s. | * Make sure to remove {{ic|quiet}} from the [[kernel parameter]]s. | ||
* Late KMS starting may cause the first few boot messages to clear. See [[ | * Late KMS starting may cause the first few boot messages to clear. See [[NVIDIA#Early loading]]. | ||
}} | }} | ||
== See also == | == See also == | ||
* [[ | * [[systemd#Change default target to boot into]] | ||
* [ | * [https://www.linusakesson.net/programming/tty/ The TTY demystified] | ||
* [[Wikipedia: | * [[Wikipedia:tty (unix)]] |
Latest revision as of 20:57, 20 May 2023
A getty is the generic name for a program which manages a terminal line and its connected terminal. Its purpose is to protect the system from unauthorized access. Generally, each getty process is started by systemd and manages a single terminal line.
Installation
agetty is the default getty in Arch Linux, as part of the util-linux package.
Alternatives include:
- mingetty — A minimal getty which allows automatic logins.
- mgetty — A versatile program to handle all aspects of a modem under Unix.
Tips and tricks
Staircase effect
agetty modifies the TTY settings while waiting for a login so that the newlines are not translated to CR-LFs. This tends to cause a "staircase effect" for messages printed to the console.
It is entirely harmless, but in the event it persists once logged, you can fix this behavior with:
$ stty onlcr
See this forums discussion on the subject.
Add additional virtual consoles
Agetty manages virtual consoles and six of these virtual consoles are provided by default in Arch Linux. They are usually accessible by pressing Ctrl+Alt+F1
through Ctrl+Alt+F6
.
Open the file /etc/systemd/logind.conf
and set the option NAutoVTs=6
to the number of virtual terminals that you want at boot.
If needed, it is possible to temporarily start a getty@ttyN.service
service directly.
Automatic login to virtual console
Configuration relies on systemd unit drop-in files to override the default parameters passed to agetty.
Configuration differs for virtual versus serial consoles. In most cases, you want to set up automatic login on a virtual console, (whose device name is ttyN
, where N
is a number). The configuration of automatic login for serial consoles will be slightly different. Device names of the serial consoles look like ttySN
, where N
is a number.
Virtual console
Create a drop-in file for getty@tty1.service
with the following contents:
/etc/systemd/system/getty@tty1.service.d/autologin.conf
[Service] ExecStart= ExecStart=-/sbin/agetty -o '-p -f -- \\u' --noclear --autologin username %I $TERM
- The option
Type=idle
found in the defaultgetty@.service
will delay the service startup until all jobs (state change requests to units) are completed in order to avoid polluting the login prompt with boot-up messages. When starting X automatically, it may be useful to startgetty@tty1.service
immediately by addingType=simple
into the drop-in file. Both the init system and startx can be silenced to avoid the interleaving of their messages during boot-up. - See Silent boot#agetty for an example virtual console drop-in file which hides the login prompt completely.
- The above snippet will cause the loginctl session type to be set to
tty
. If desirable (for example if starting X automatically), it is possible to manually set the session type towayland
orx11
by addingEnvironment=XDG_SESSION_TYPE=x11
orEnvironment=XDG_SESSION_TYPE=wayland
into this file.
If you do not want full automatic login, but also do not want to type your username, see #Prompt only the password for a default user in virtual console login.
If you want to use a tty other than tty1, see systemd/FAQ#How do I change the default number of gettys?.
Serial console
Create a drop-in file:
/etc/systemd/system/serial-getty@ttyS0.service.d/autologin.conf
[Service] ExecStart= ExecStart=-/sbin/agetty -o '-p -f -- \\u' --keep-baud --autologin username 115200,57600,38400,9600 - $TERM
Nspawn console
To configure auto-login for a systemd-nspawn container, override console-getty.service
by creating a drop-in file:
/etc/systemd/system/console-getty.service.d/autologin.conf
[Service] ExecStart= ExecStart=-/sbin/agetty -o '-p -f -- \\u' --noclear --keep-baud --autologin username - 115200,38400,9600 $TERM
If machinectl login my-container
method is used to access the container, also adjust the container-getty@.service
template that manages pts/[0-9]
pseudo ttys:
/etc/systemd/system/container-getty@.service.d/autologin.conf
[Service] ExecStart= ExecStart=-/sbin/agetty -o '-p -f -- \\u' --noclear --keep-baud --autologin username - 115200,38400,9600 $TERM
Prompt only the password for a default user in virtual console login
Getty can be used to login from a virtual console with a default user, typing the password but without needing to insert the username. For instance, to prompt the password for username
on tty1
:
/etc/systemd/system/getty@tty1.service.d/skip-username.conf
[Service] ExecStart= ExecStart=-/sbin/agetty -o '-p -- username' --noclear --skip-login - $TERM
and then enable getty@tty1
.
Have boot messages stay on tty1
By default, Arch has the getty@tty1
service enabled. The service file already passes --noclear
, which stops agetty from clearing the screen. However systemd clears the screen before starting it. To disable this behavior, create a drop-in file:
/etc/systemd/system/getty@tty1.service.d/noclear.conf
[Service] TTYVTDisallocate=no
- Make sure to remove
quiet
from the kernel parameters. - Late KMS starting may cause the first few boot messages to clear. See NVIDIA#Early loading.