As we know there’s a kind of read-only variables in bash in common linux system, typically $BASH_COMPLETION and $BASH_COMPLETION_DIR are both readonly variables. This post will focus on the following two topics, how can we set readonly variables in Bash, and how can we unset them.

In some sort of problems, ext3 goes read-only to protect the filesystem against further damages. What could cause such a readonly problem? It’s difficult to get an exact answer, but I’m inclined to take it as a file-system issue, though some hardware problems will trigger this error as well.