The answer is rsync -a --link-dest=/previous/backup /source /current/backup, because the --link-dest option instructs rsync to create hard links pointing to files in the specified previous backup directory whenever a file has not changed between the source and that reference directory. This enables an incremental backup strategy where only new or modified files consume additional disk space, while unchanged files are represented as hard links, dramatically reducing storage overhead. On the CompTIA Linux+ XK0-005 exam, this scenario tests your understanding of backup optimization and the distinction between hard links and symbolic links; a common trap is confusing --link-dest with --copy-dest, which copies files instead of linking them. Remember the mnemonic "Link to the past" to recall that --link-dest references an earlier backup directory for unchanged files.
XK0-005 System Management Practice Question
This XK0-005 practice question tests your understanding of system management. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A system administrator needs to configure a daily backup that creates hard links to unchanged files to save space. Which tool and option combination is most appropriate?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
rsync -a --link-dest=/previous/backup /source /current/backup
Option A is correct. rsync with --link-dest creates hard links to unchanged files, enabling incremental backups. Option B copies with hard links but not incremental. Option C does not handle incremental hard links. Option D is for disk cloning.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
dd if=/source of=/destination conv=sync
Why it's wrong here
dd is used for low-level copying; it does not support hard links or incremental backups.
✗
cp -al /source /destination
Why it's wrong here
This creates a hard-linked copy of the entire directory tree, but does not provide incremental backup; all files are copied each time.
✓
rsync -a --link-dest=/previous/backup /source /current/backup
Why this is correct
rsync --link-dest creates hard links to files in the previous backup that have not changed, saving disk space.
Related concept
Static NAT maps one inside address to one outside address.
✗
tar --hard-link --create /source > /destination/backup.tar
Why it's wrong here
tar does not natively support incremental hard-link backups; it creates an archive.
Common exam traps
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A small business has 20 workstations on the 192.168.1.0/24 network and one public IP from its ISP. The router uses PAT (NAT overload) so all 20 devices share one public address using different source ports. NAT questions test whether you understand the four address terms and which direction each translation applies.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this XK0-005 question in full detail.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related XK0-005 NAT questions on configuration and troubleshooting.
System Management — This question tests System Management — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: rsync -a --link-dest=/previous/backup /source /current/backup — Option A is correct. rsync with --link-dest creates hard links to unchanged files, enabling incremental backups. Option B copies with hard links but not incremental. Option C does not handle incremental hard links. Option D is for disk cloning.
What should I do if I get this XK0-005 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related XK0-005 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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