On an Ubuntu installation managed by systemd, start with the service journal rather than guessing a file path. Identify the unit, then run sudo journalctl -u redis-server.service -n 100 --no-pager. If the unit is named redis.service, substitute that name. File logs may exist under /var/log/redis/, but only the active logfile setting in Redis’s configuration tells you whether a file is being written and where.
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Find the Redis service name first
Ubuntu installations do not all use the same systemd unit name. Packages and installation methods commonly expose either redis-server.service or redis.service. Querying the wrong name produces an empty result or an error even when Redis is running, so confirm the unit before reading logs.
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systemctl list-units --type=service | grep -E 'redis|redis-server'. - Look for an entry ending in
.serviceand note its exact spelling. - Check its state and recent status output, replacing the example unit if necessary:
sudo systemctl status redis-server.service.
The status screen shows whether the service is active, the main process ID, recent output, and the unit file being used. It is a useful first check, but it displays only a small recent portion of the journal. Use journalctl for a complete query.
Read Redis logs with journalctl
journalctl is the systemd utility for querying the journal. A systemd-managed Redis process can send startup messages, shutdown notices, warnings, and errors there even when no traditional log file exists.
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Show the most recent records
Display the last 100 entries without opening an interactive pager:
sudo journalctl -u redis-server.service -n 100 --no-pager-u filters by systemd unit, -n 100 limits the output to the newest 100 records, and --no-pager prints directly to the terminal. Increase or decrease the number to fit the incident you are investigating.
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To remove older boots from the result, add -b:
sudo journalctl -u redis-server.service -bThis is especially useful after a restart. It tells you what this boot recorded without mixing it with an earlier failed start. If your unit is redis.service, run sudo journalctl -u redis.service -b instead.
Filter by a time window
Use the journal’s relative time syntax when you know approximately when a problem occurred:
sudo journalctl -u redis-server.service --since '1 hour ago'You can replace the expression with another time understood by journalctl, such as a specific date and time. Keep the unit filter in place so unrelated system messages do not obscure Redis events.
Follow new messages in real time
To watch records as Redis writes them, combine follow mode with the unit filter:
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sudo journalctl -fu redis-server.service-f follows the journal, while -u restricts output to Redis. Reproduce the failure or restart the service in another terminal; new messages will appear immediately. Press Ctrl+C to stop following.
Inspect the unit when output is unexpected
If the journal is empty, the service name may be wrong or the unit may launch Redis with a different output configuration. Display the complete unit definition:
sudo systemctl cat redis-server.serviceReplace the unit name if needed. Pay attention to the ExecStart command and any service-level output directives. The command reveals which configuration file or wrapper the service actually uses, so you can compare it with the file you inspected manually.
Check file-based Redis logs and configuration
The Ubuntu redis-server package provides /etc/redis/redis.conf, a systemd unit, and a logrotate rule at /etc/logrotate.d/redis-server. Those files establish the usual package layout, but the active configuration still determines whether Redis writes a file.
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Read the active logging directives
Extract the relevant settings from the package configuration:
sudo grep -E '^(logfile|syslog-enabled|daemonize)' /etc/redis/redis.conflogfilecontrols the destination when file logging is configured. The value may be a path different from the commonly seen/var/log/redis/redis-server.log.syslog-enabledindicates whether Redis is configured to use syslog facilities rather than (or in addition to) a file, depending on the rest of the configuration and service setup.daemonizeaffects how Redis runs. A service launched under systemd may be configured to remain in the foreground so systemd can capture its output.
These lines can be commented out, overridden by another configuration file, or superseded by command-line options in ExecStart. If the values do not explain the running process, inspect the unit with systemctl cat and verify its start command.
Inspect the expected directory
sudo ls -la /var/log/redisIf a file log is configured at the package’s conventional location, view its newest records with:
sudo tail -n 100 /var/log/redis/redis-server.logA missing redis-server.log does not by itself indicate a Redis failure. The service may be sending output to journald, the configured logfile may point elsewhere, the directory may have different permissions, or Redis may not have emitted a record yet. Confirm the destination before creating files or changing permissions.
Understand rotation
Ubuntu includes /etc/logrotate.d/redis-server for package-managed file logs. Logrotate can rename or compress older files, so a current directory listing may contain rotated names rather than one continuously growing file. The rotation rule is relevant only when Redis is actually writing to files; journal records are retained according to journald’s own limits.
Journal versus file logs: what changes for you?
| Aspect | systemd journal | Redis file log | Redis Software |
|---|---|---|---|
| Typical destination | Systemd journal, queried with journalctl -u <unit> |
Path set by logfile, often under /var/log/redis/ on Ubuntu package installations |
By default under /var/opt/redislabs/log/ |
| How to locate it | Confirm the unit, then filter with journalctl |
Read /etc/redis/redis.conf and list the configured directory |
Use Redis Software’s product-specific layout |
| Retention | Controlled by journald storage and size limits | Controlled by the logrotate policy and filesystem space | Controlled by Redis Software’s logging and retention setup |
| Service name | Usually redis-server.service or redis.service for Ubuntu installs |
Uses the same systemd unit that launches Redis | Not interchangeable with the Ubuntu open-source package unit |
| Permissions | Reading system-wide records commonly requires sudo |
Directory and file permissions determine who can read them | Product installation permissions apply |
The /var/opt/redislabs/log/ location belongs to Redis Software, a separate product. Do not use it as the expected path for a normal Ubuntu redis-server package installation.
Why older journal entries may be missing
Finding only recent Redis messages can be a retention issue rather than evidence that Redis never logged the event. Ubuntu’s systemd-journald documentation describes two storage locations:
/var/log/journalis the persistent location. Entries can survive a reboot when persistent storage is configured and space limits permit./run/log/journalis volatile runtime storage. Entries there are lost when the system reboots.
Check how much space the journal uses and which directories exist:
journalctl --disk-usage
sudo ls -ld /var/log/journal /run/log/journalReview the configured storage and limits:
sudo grep -E '^(Storage|SystemMaxUse|RuntimeMaxUse)=' /etc/systemd/journald.confAn absent /var/log/journal directory, a Storage=volatile setting, or a runtime-size limit explains why records from a previous boot are unavailable. These checks describe journal retention; they do not change it. If you need durable history, configure journald persistence and appropriate limits according to your Ubuntu administration policy, then restart or reload journald as required by that policy.
A complete troubleshooting workflow
Use this sequence when a Redis log command returns nothing, the expected file is missing, or you are diagnosing a failed start.
1. Confirm that a Redis service exists
systemctl list-units --type=service | grep -E 'redis|redis-server'If this returns no loaded unit, Redis may not be installed as a systemd service, may use a differently named unit, or may not currently be loaded. Check the installation method before assuming a package layout.
2. Check service state and recent output
sudo systemctl status redis-server.serviceRead the exact unit name from the command’s output. A failed state, exit status, or start-limit message gives you a direction for the journal query.
3. Query this boot’s records
sudo journalctl -u redis-server.service -bLook for configuration parse errors, permission failures, address-in-use messages, clean shutdowns, and restart attempts. Keep the output tied to the unit you confirmed.
4. Narrow the time range
sudo journalctl -u redis-server.service --since '1 hour ago'Use a narrow interval around the incident to reduce noise. For a known restart, query from just before that event through the present.
5. Follow a reproduction
sudo journalctl -fu redis-server.serviceLeave this command running, reproduce the client error or restart, and capture the resulting records. This distinguishes a one-time startup problem from an ongoing runtime warning.
6. Verify file logging settings
sudo grep -E '^(logfile|syslog-enabled|daemonize)' /etc/redis/redis.conf
sudo ls -la /var/log/redisRead the actual logfile value instead of assuming /var/log/redis/redis-server.log. If it points to another path, inspect that path and its parent-directory permissions.
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sudo systemctl cat redis-server.serviceRepeat with redis.service if that is the unit you found. Compare ExecStart with the configuration file you examined. A command-line configuration path or wrapper script can explain why the expected file remains empty.
8. Check retention when history is absent
journalctl --disk-usage
sudo ls -ld /var/log/journal /run/log/journal
sudo grep -E '^(Storage|SystemMaxUse|RuntimeMaxUse)=' /etc/systemd/journald.confIf the event predates a reboot and the journal is volatile, it cannot be recovered from that host’s journal. Check rotated file logs or a central logging system if your environment forwards records elsewhere.
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Common failure modes and their fixes
“No entries” from journalctl
The most common cause is a unit-name mismatch. Run the unit-list command again and query both documented names if necessary:
sudo journalctl -u redis-server.service -n 100 --no-pager
sudo journalctl -u redis.service -n 100 --no-pagerIf both are empty, verify that Redis is running under systemd and inspect the unit definition. A manually launched process may not have a matching systemd unit.
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Check logfile, syslog-enabled, and the unit’s ExecStart. The service may intentionally log only to journald, use a different path, or have produced no output. Do not create a blank file and infer that Redis will use it; the configured destination controls behavior.
Permission denied while reading
Use sudo for system journal queries and protected log directories. For a custom file destination, inspect ownership and mode with ls -la. Avoid broad permission changes; grant only the operators or service accounts that need access.
Logs disappeared after reboot
Inspect /var/log/journal, /run/log/journal, and journald’s Storage setting. Volatile storage under /run/log/journal is cleared at reboot, while persistent history depends on /var/log/journal and retention limits.
There are several similarly named files
File logging may be rotating through the rule in /etc/logrotate.d/redis-server. Sort the directory by modification time and inspect the active and rotated files. Then compare their timestamps with the journal so you do not mistake an archived file for the current stream.
Redis Software is a different installation
Redis Software is separate from the Ubuntu open-source redis-server package. Its documentation places server logs by default under /var/opt/redislabs/log/ and identifies event_log.log for configuration actions. That path should be used only when Redis Software is actually installed. Applying it to a package-managed Ubuntu server can waste time and lead you away from the correct systemd unit and configuration.
Quick Recap
Quick command checklist
- Discover the unit:
systemctl list-units --type=service | grep -E 'redis|redis-server' - Check status:
sudo systemctl status redis-server.service - Read recent records:
sudo journalctl -u redis-server.service -n 100 --no-pager - Read this boot:
sudo journalctl -u redis-server.service -b - Filter by time:
sudo journalctl -u redis-server.service --since '1 hour ago' - Follow live output:
sudo journalctl -fu redis-server.service - Inspect the unit:
sudo systemctl cat redis-server.service - Check file logging:
sudo grep -E '^(logfile|syslog-enabled|daemonize)' /etc/redis/redis.conf - Inspect the conventional directory:
sudo ls -la /var/log/redis - Check journal retention:
journalctl --disk-usage
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