IKM System Administration Fundamentals 2 — Questions and Answers
Question 1: What is the purpose of a cron job?
- Monitor CPU temperature
- Schedule commands to run automatically at specified times (Correct answer)
- Manage passwords
- Compress logs manually
Correct answer: Schedule commands to run automatically at specified times
Cron is a time-based scheduler executing commands at specified times or intervals.
Uses five time fields: minute, hour, day of month, month, day of week. 'crontab -e' edits user crontabs. Systemd timers are a modern alternative.
Question 2: What does /etc/passwd contain?
- Encrypted passwords
- User account info: username, UID, GID, home directory, shell (Correct answer)
- Password policies
- Failed login logs
Correct answer: User account info: username, UID, GID, home directory, shell
/etc/passwd contains user account information, not actual passwords.
Format: username:x:UID:GID:comment:home:shell. The 'x' means passwords are in /etc/shadow. UID 0 is root, 1-999 system accounts, 1000+ regular users.
Question 3: What is the difference between hard and symbolic links?
- Hard links cross file systems
- Hard links point to the inode; symbolic links point to the file path (Correct answer)
- Symlinks cannot be created by users
- No practical difference
Correct answer: Hard links point to the inode; symbolic links point to the file path
Hard links share the same inode; symbolic links contain the target path.
Hard links cannot cross file systems or link to directories. Deleting one hard link does not affect others. Symbolic links can cross file systems and link to directories but break if the target is deleted.
Question 4: What does chmod do?
- Change ownership
- Change file access permissions (Correct answer)
- Change modification time
- Change file name
Correct answer: Change file access permissions
chmod modifies read, write, and execute permissions for owner, group, and others.
Numeric: r=4, w=2, x=1 (755 = rwxr-xr-x). Symbolic: u+x adds execute for owner. Special permissions: setuid, setgid, sticky bit.
Question 5: What is LVM used for?
- Network volumes
- Flexible disk storage by abstracting physical disks into logical volumes (Correct answer)
- Disk health monitoring
- Disk encryption
Correct answer: Flexible disk storage by abstracting physical disks into logical volumes
LVM provides flexible creation, resizing, and management of logical volumes.
Three layers: Physical Volumes, Volume Groups (pool), Logical Volumes (virtual partitions). Key benefits: online resize, spanning, snapshots, live data migration.
Question 6: What is SSH key-based authentication?
- Speed up connections
- Secure password-less authentication using public-private key pairs (Correct answer)
- Encrypt DNS queries
- Manage SSL certs
Correct answer: Secure password-less authentication using public-private key pairs
SSH keys provide stronger security than passwords and enable automated logins.
Public key in authorized_keys on server. Server sends challenge encrypted with public key; only the matching private key can decrypt. Supports Ed25519 and RSA.
IKM System Administration Fundamentals 2
What is the purpose of a cron job?