Hosting Operations
Read-onlyDry-Run Logrotate Before Touching Logs
You need to understand what logrotate would do without compressing, renaming, or truncating real logs.
Command
logrotate -d /etc/logrotate.conf 2>&1 | sed -n '/rotating pattern/p;/considering log/p;/error:/p'Before you run this
System impact: Read-only. Low when scoped to the shown target.
When not to use it: Do not use -f unless you intentionally want to force rotation; this lesson is debug-only.
Expected output
rotating pattern and considering log lines from logrotate debug output.
System impact
Read-only. Nothing changes. The -d flag runs logrotate in debug mode and the pipe extracts useful decision lines.
May require elevated permissions on protected paths or service-owned files.
Recovery / rollback: no state is changed.
When to use it
Use before changing logrotate rules or when logs are growing and you need to see whether policies match them.
When not to use it
Do not use -f unless you intentionally want to force rotation; this lesson is debug-only.
Watch this command run
Command transcript
This sanitized transcript shows the commands and output shape without exposing host details.
$ logrotate -d /etc/logrotate.conf
reading config file /etc/logrotate.conf
including /etc/logrotate.d
reading config file nginx
reading config file app
rotating pattern: /var/log/nginx/*.log after 1 days (14 rotations)
considering log /var/log/nginx/access.log
log does not need rotating
considering log /var/log/nginx/error.log
log does not need rotating
rotating pattern: /var/log/app/app.log 52428800 bytes (7 rotations)
considering log /var/log/app/app.log
log does not need rotating$ logrotate -d /etc/logrotate.conf 2>&1 | sed -n '/rotating pattern/p;/considering log/p;/error:/p'
rotating pattern: /var/log/nginx/*.log after 1 days (14 rotations)
considering log /var/log/nginx/access.log
considering log /var/log/nginx/error.log
rotating pattern: /var/log/app/app.log 52428800 bytes (7 rotations)
considering log /var/log/app/app.logView commands shown
These are the commands shown in the sanitized transcript.
Commands shown
logrotate -d /etc/logrotate.conflogrotate -d /etc/logrotate.conf 2>&1 | sed -n '/rotating pattern/p;/considering log/p;/error:/p'
next steps
Related commands
Find Logs Missing Logrotate Coverage
The biggest log risk is often the file no policy mentions.
find /var/log -type f -name '*.log' -printf '%p\n' | while read -r log; do grep -Rqs -- "$log" /etc/logrotate.conf /etc/logrotate.d || grep -Rqs -- "$(dirname "$log")/[*].log" /etc/logrotate.conf /etc/logrotate.d || printf '%s\n' "$log"; done
Scan Every CI Log for Error Lines
One grep pass can turn a log pile into a failure list.
grep -RInE 'error|failed|failure|exception|traceback' artifacts logs | head -50
Review Log Files Before Cleanup
Before truncating logs, prove which log files are large and how old they are.
find /lab/disk-inode-cleanup/var/log -xdev -type f -printf '%10s %TY-%Tm-%Td %p\n' | sort -nr
Count Request IDs in Error Lines
Repeated request IDs can connect separate error lines to one failing path.
grep -Ei 'error|timeout|fatal|exception' fixtures/incidents/app.log | awk '{for (i=1;i<=NF;i++) if ($i ~ /^request_id=/) print $i}' | sort | uniq -c | sort -nr
Tail the Failing CI Lines
Skip the full CI log and jump straight to lines that usually explain the failure.
grep -RInE 'error|failed|exception|traceback|fatal' logs/ | tail -50
Study mapping
Use this as independent command practice: read the notes, predict the output, then compare it with the example before using a real shell.
Useful for
- LPIC-1 style command-line practice
- LFCS style performance tasks
- Linux+ style troubleshooting review
Independent study support only. No affiliation, endorsement, exam dumps, or real exam questions.