5 Data
Every entry filed under Data and its subtopics.
What kind of help
Works on
What do these mean?
- Beginner
- You are new to this topic.
- Intermediate
- You use it, and want to get better.
- Advanced
- You know it well and need the details.
- Guided project
- Build something small from start to finish, step by step.
- Explains an idea
- Plain words on how something works and why.
- Step by step
- Numbered steps to get one task done.
- Cheat sheet
- Commands and options in a table, to look up fast.
- Fixes an error
- An error message, what it means, and how to solve it.
9 entries match these filters
- 0324 Fix: psql: FATAL: Peer authentication failed On local socket connections PostgreSQL checks that your OS user name equals the database role. When they differ you get this error.… Intermediate · Fixes an error · Linux Article Install & connect · Security & access 15 Oct 2026
- 0326 Fix: too many open files A process hit its file descriptor limit, usually 1024. Raise it for the shell, the systemd unit or the user, fix a… Intermediate · Fixes an error · Linux, macOS Article Performance & tuning · Processes & ports · Services & systemd 15 Oct 2026
- 0235 Fix: MongoServerSelectionError: connect ECONNREFUSED 127.0.0.1:27017 Your app or tool tried to reach MongoDB on port 27017 and nothing accepted the connection. Usually mongod is not running, crashed… Intermediate · Fixes an error · Linux, macOS, Windows Article Administration · Basics 15 Oct 2026
- 0240 Fix: MISCONF Redis is configured to save RDB snapshots, but it’s currently unable to persist to disk Redis blocks writes because its last background snapshot failed. Find the cause in the log (full disk, permissions, failed fork), fix it,… Intermediate · Fixes an error · Linux Article Administration & persistence 15 Oct 2026
- 0209 Fix: FATAL: password authentication failed for user PostgreSQL reached the server and found a matching pg_hba.conf rule, but the password check failed. Usually a wrong password, a role without… Intermediate · Fixes an error · Any system Article Roles & administration · Security & access 15 Oct 2026
- 0210 Fix: FATAL: no pg_hba.conf entry for host The server received the connection but no pg_hba.conf rule matches this client address, user, database and SSL mode. Add or correct a… Intermediate · Fixes an error · Linux Article Install & connect · Security & access 15 Oct 2026
- 0226 Fix: ORA-12541: TNS:no listener The client reached the host but nothing was listening on that port. Start or fix the Oracle listener, or correct the host… Intermediate · Fixes an error · Linux, Windows Article Administration · Concepts & tools 15 Oct 2026
- 0227 Fix: ORA-01017: invalid username/password; logon denied Oracle rejected the login. Check the password (case-sensitive), that you connect to the right PDB service, and whether the account is locked… Intermediate · Fixes an error · Any system Article Administration · Security & access 15 Oct 2026
- 0071 Fix: column “x” must appear in the GROUP BY clause or be used in an aggregate function PostgreSQL rejects a grouped query that selects a column with more than one possible value per group. Add the column to GROUP… Intermediate · Fixes an error · Any system Article Queries 15 Oct 2026