Lecture 5. Permissions part 1: ls -l anatomy, rwx, file types

Exam questions that cite this lecture

• CSCD240-E1-A-Q04 permissions Given -rw-r-x--x 2 ssteiner faculty 4096 Apr 14 09:30 notes.sh — what does the - as first symbol mean?
• CSCD240-E1-A-Q05 permissions-anatomy Describe what r, w, x, and - mean and what each group of three symbols means.
• CSCD240-E1-A-Q06 permissions First symbol d — what does this mean?
• CSCD240-E1-A-Q07 permissions First symbol l — what does this mean?
• CSCD240-E1-A-Q08 permissions What does 4096 refer to in the ls -l line?
• CSCD240-E1-A-Q09 permissions Who owns this file?
• CSCD240-E1-A-Q10 permissions What group does this file belong to?
• CSCD240-E1-A-Q41 setuid Explain the setuid bit in 1-2 sentences using the term "effective user ID".
• CSCD240-E1-A-Q45 command-substitution Print "Backup taken on <today>" using $(date +%Y-%m-%d) as the date.
• CSCD240-E1-B-Q05 permissions First symbol - on /usr/bin/passwd means what?
• CSCD240-E1-B-Q06 permissions-special Owner triad shows rws instead of rwx. Name the bit.
• CSCD240-E1-B-Q07 setuid-effect What does the setuid bit cause when the file is executed? Use "effective user ID".
• CSCD240-E1-B-Q08 setuid-chain Who owns /usr/bin/passwd in the ls -l line? Why does that matter for setuid?
• CSCD240-E1-B-Q41 command-subst Print "Backup taken on <today>" using $(date +%F).
• CSCD240-E1-C-Q04 setuid A -rwsr-xr-x file owned by root. Execution causes what?
• CSCD240-E1-C-Q06 cmd-subst Recommended modern syntax for command substitution?
• CSCD240-E1-C-Q07 permissions First character of ls -l that identifies a symbolic link?
• CSCD240-E1-C-Q16 permissions-special What does the sticky bit on a directory do?
• CSCD240-E1-C-Q41 threat-reasoning -rwsrwxrwx root root .xhelper in /tmp. Why alarming?
• CSCD240-E1-C-Q47 ssh-perms -rw------- on .ssh and drwx------ on .config — which is typical for an SSH private key and why?