cloud engineer
Here’s how to run Rocky Linux in a Docker container.
Download the image.
docker pull rockylinux/rockylinux |
docker pull rockylinux/rockylinux
Create a Rocky Linux container called bullwinkle.
docker run -it --name bullwinkle -d rockylinux/rockylinux |
docker run -it --name bullwinkle -d rockylinux/rockylinux
Login to the container using bash.
docker exec -it --user root bullwinkle /bin/bash |
docker exec -it --user root bullwinkle /bin/bash
When done, stop and delete the container.
docker ps -a docker stop container_ID docker rm container_ID |
docker ps -a docker stop container_ID docker rm container_ID
Here’s how to check in Bash if a variable is empty or unset.
if [ -z "${VAR}" ]; then echo 'do something' else echo 'do another' fi |
if [ -z "${VAR}" ]; then echo 'do something' else echo 'do another' fi
One liner
if [ -z "${VAR}" ]; then echo 'do something'; else echo 'do another'; fi |
if [ -z "${VAR}" ]; then echo 'do something'; else echo 'do another'; fi
The inverse
if [ ! -z "${VAR}" ]; then echo 'do something' else echo 'do another' fi |
if [ ! -z "${VAR}" ]; then echo 'do something' else echo 'do another' fi
if [ ! -z "${VAR}" ]; then echo 'do something'; else echo 'do another'; fi |
if [ ! -z "${VAR}" ]; then echo 'do something'; else echo 'do another'; fi
If you want to SSH to a Docker container, use the Docker exec command.
docker exec -it container_name bash |
docker exec -it container_name bash
I’m using a Git Bash terminal, so I have to prefix the docker command with winpty.
winpty docker exec -it container_name bash |
winpty docker exec -it container_name bash
Result
root@681bbe3f65f1:/var/www/html# |
root@681bbe3f65f1:/var/www/html#
Ctrl-D to exit.
Here’s a simple little script that displays the number of characters in a string.
#!/bin/bash if [[ $# -eq 0 ]] ; then echo 'Missing arguments'; exit 0; fi var=$1 size=${#var} echo $size |
#!/bin/bash if [[ $# -eq 0 ]] ; then echo 'Missing arguments'; exit 0; fi var=$1 size=${#var} echo $size
Command:
./length.sh abcdefghijklmnopqrstuvwxyz |
./length.sh abcdefghijklmnopqrstuvwxyz
Output:
26 |
26
I decided to log my commands for good record keeping. Here’s my script.
#!/bin/bash if [[ $# -eq 0 ]] ; then echo 'No arguments. Format: ./go.sh script.sh'; exit 0; fi log=log.txt echo '-------------------------------' >> $log date >> $log echo '---' >> $log cat $1 >> $log echo '---' >> $log /bin/bash $1 2>&1 | tee -a $log |
#!/bin/bash if [[ $# -eq 0 ]] ; then echo 'No arguments. Format: ./go.sh script.sh'; exit 0; fi log=log.txt echo '-------------------------------' >> $log date >> $log echo '---' >> $log cat $1 >> $log echo '---' >> $log /bin/bash $1 2>&1 | tee -a $log
To run.
./go.sh script.sh |
./go.sh script.sh
Line by line explanation.