Shell scripting concepts covered in this lesson:

• Deleting users with the userdel command.

• Expiring and locking accounts with the chage command.

• How to find commands not in your PATH.

• Using the locate and find commands.

• Matching patterns with the grep command.

• Using the !! and !$ event designators to speed up your workflow at the command line.

• UID for system accounts and normal user accounts.

• Creating and restoring backups and archives with the tar command.

• How to compress files with gzip and uncompress them with gunzip.

• Why not to lock accounts with the passwd command or by using the nologin shell.