Uly.me

cloud engineer

shell

SSSD Override Shell

If you have SSSD running and the default shell is ksh even with the default shell set to bash.

Here’s the fix to override the default shell in /etc/sssd/sssd.conf. Add override_shell.

default_shell = /bin/bash
override_shell = /bin/bash

To check which shell you are using.

echo $SHELL
/bin/bash

GCP Cloud Shell Vim Settings

I had an issue with using the backspace in Vim in GCP’s Cloud Shell. Every time I’m in the insert mode and I want to edit using backspace, it doesn’t delete the characters. It shows these characters “^?” instead. Well, it turned out to be a backspace setting that you can set within .vimrc. So, here’s my working setup.

colo desert
syntax on
set backspace=indent,eol,start
  • The first line uses the desert theme.
  • The second line turns on syntax highlighting. It’s on by default.
  • The third line fixes the backspace issue I mentioned above.

Linux Useradd

Here’s the command to add a Linux user.

useradd -m -s $(which bash) -G sudo ulysses

-m creates a home directory. -s selects a shell. -G adds user to a sudo group.

GCloud Interactive Shell

If you already have Google SDK installed, you can activate GCloud Interactive Shell, which is still in beta by the way, by typing the following command from the Google SDK terminal.

gcloud beta interactive

The interactive shell environment has auto-completion. It shows you who’s logged in and which project you are currently set in. To exit the interactive shell, just Press F9 to quit.

Run Shell Script From Your Website

Here’s how to run a shell script from your website. You’ll need 2 files.

Here’s the contents of foo.php. Wrap your output with ‘pre’ for better formatting.

<?php
$output = shell_exec('/var/www/html/bar.sh 2>&1');
echo "$output";

Here’s the content of bar.sh. Output will be displayed on web page.

#!/bin/bash
now="$(date +'%y%m%d')"
echo $now
aws s3 ls

Which shell is running

Here’s how to find out which shell you are running. Run any of the 3 commands below.

echo $0
echo $SHELL
ps -p "$$"

Bash Source in Cron

I’m running a “source” command inside a Bash script. The script is running fine on its own, but when I try running it inside a crontab, it doesn’t work. I’m using the source command just to load variables in a file, so I don’t have to edit multiple files. As it turns out, the regular shell in crontab does not quite understand the source command, and it’s the very reason the script fails. Here’s an example.

source /home/user/server.conf

I ended up removing the source line, and hardcoding the variables instead of loading it from a file.

server="servername"