This and sed

Sed is a nice little tool that is quite hard to understand. While a longer tutorial can be found here. I found it especially useful for editing config files.

If you want to deny root login via ssh you can simply enter this command: 
# sudo sed -ir 's/^(PermitRootLogin) .+/\1 no/' /etc/ssh/sshd_config


It uses pattern matching a la perl and s/ searches for a line that ^starts with "PermitRootLogin" followed by one or more other characters. After the second slash we enter how it is replaced and here \1 fills in the bracketed "PermitRootLogin" string and then we add "no".

In Perl this would look like this: 
# sudo perl -pi -e 's/^PermitRootLogin.+/PermitRootLogin no/'  /etc/ssh/sshd_config



Kommentare

Kommentar veröffentlichen

Beliebte Posts aus diesem Blog

Ubuntu 16.04.2 Kiosk Mode

If you want to run a PC in Kiosk mode, you probably want to run an instance of a web browser that does not allow anything else but simple browsing with only the mouse. The browser is not supposed to be canceled or quit but should indefinitely run and provide the specified web page you want to provide the kiosk for. This would entail booting the PC directly into the web browser. Setup: In this example we use the chromium open source chrome derivate web browser that will connect to a specified web page and will function in kiosk mode just in the way you would expect it to run. This howto is addressed to intermediate users that have a basic understanding of the linux shell, that are able edit script files and know what ~ means. In order to achieve this goal we can create a simple Ubuntu server installation and just install the bare minimum of packages required to fulfill our task. In part I will rely on the very helpful but a bit outdated example from Oli Warner. Installation of U
Weiterlesen

What To Do When Your Ubuntu System Hangs On Reboot Or Shutdown?

When Linux hangs or freezes during the shutdown or reboot sequence, especially during remote sessions where no physically attached keyboard can be accessed, you may want to make sure the server will reboot no matter what and apply the -f parameter to force immediate shutdown: reboot -f In other situations where you may have a keyboard at hand and want to debug shutdown hangs, you may find the not so well known Magic SysRq keyboard shortcuts come in handy. Pressing CTRL+PRINT+B will immediately reboot your system without invoking the init system and even when the systemd debug console won't accept any keyboard inputs anymore.
Weiterlesen