Articles

35 entries match these filters

0007 Fix: ModuleNotFoundError: No module named ‘…’ Python cannot find a module you import. Usually the package was installed into a different interpreter or virtual environment than the one… Beginner · Fix · Any system Article Common errors · Environments & packages 15 Oct 2026
0008 Fix: TypeError: ‘NoneType’ object is not subscriptable You used [ ] on a value that is None. Something you expected to return a list, dict or match returned nothing.… Beginner · Fix · Any system Article Common errors 15 Oct 2026
0026 Fix: TypeError: Cannot read properties of undefined (reading ‘x’) You tried to read a property from a value that is undefined or null. Find which value is missing, then guard it… Beginner · Fix · Any system Article Basics · Common errors 15 Oct 2026
0027 Fix: SyntaxError: Cannot use import statement outside a module The file uses ES module import syntax, but Node or the browser is loading it as a classic script or CommonJS. Tell… Intermediate · Fix · Any system Article Common errors · Node.js 15 Oct 2026
0040 Fix: error: failed to push some refs to … Git refused your push, usually because the remote branch has commits you do not have yet. Bring them in, combine them with… Beginner · Fix · Any system Article Common errors 15 Oct 2026
0041 Fix: CONFLICT (content): Merge conflict in … Two branches changed the same lines and Git cannot choose for you. Open the file, keep the right text, remove the markers,… Intermediate · Fix · Any system Article Branching & rebasing · Common errors 15 Oct 2026
0042 Fix: fatal: refusing to merge unrelated histories Your local repository and the remote do not share a single commit, usually because both were started separately. Allow the one-time merge,… Intermediate · Fix · Any system Article Common errors 15 Oct 2026
0054 Fix: Permission denied (publickey) The server refused every key your SSH client offered. Find out which key was offered, make sure its public half is on… Intermediate · Fix · Linux, macOS, Windows Article Keys & config 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 · Fix · Any system Article Queries 15 Oct 2026
0073 Fix: json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0) Python's json module found nothing it could parse at the very first character. The input is usually empty, HTML, or already consumed.… Beginner · Fix · Any system Article Common errors · CSV & JSON 15 Oct 2026
0088 Fix: Access to fetch at ‘…’ from origin ‘…’ has been blocked by CORS policy The browser refused to give your script a cross-origin response because the server did not send the right Access-Control-* headers. Fix it… Intermediate · Fix · Browser Article Common errors · Making requests 15 Oct 2026
0089 Fix: 413 Request Entity Too Large A server or proxy rejected your request because its body is bigger than the configured limit. Find which layer set the limit,… Intermediate · Fix · Any system, Linux Article Status codes · Web frameworks 15 Oct 2026
0110 Fix: TASK ERROR: VM is locked (backup) A VM or container still carries a backup lock, usually after a backup was interrupted. Check that no backup is running, then… Beginner · Fix · Linux Article Backup & restore · VMs & containers 15 Oct 2026
0111 Fix: can’t lock file ‘/var/lock/qemu-server/lock-VMID.conf’ – got timeout Another task is holding the VM's local lock file, so a new action timed out waiting for it. Find the running or… Intermediate · Fix · Linux Article VMs & containers 15 Oct 2026
0112 Fix: TASK ERROR: cluster not ready – no quorum? The node is not part of a quorate cluster, so /etc/pve is read-only and guests cannot be started or changed. Restore the… Advanced · Fix · Linux Article Clusters & high availability 15 Oct 2026
0127 Fix: “Requested operation is not valid: network ‘default’ is not active” A libvirt VM will not start because the virtual network it uses, usually the NAT network 'default', is stopped. Start the network… Intermediate · Fix · Linux Article Basics 15 Oct 2026
0142 Fix: ImagePullBackOff and ErrImagePull in Kubernetes The pod cannot start because the node failed to pull the container image. Read the "Failed to pull image" event to see… Intermediate · Fix · Linux Article Troubleshooting 15 Oct 2026
0143 Fix: CrashLoopBackOff in Kubernetes The container starts, exits, and Kubernetes waits longer before each restart. Read the previous container's logs and its exit code to find… Intermediate · Fix · Linux Article Troubleshooting 15 Oct 2026
0144 Fix: Pod stuck in Pending with “0/3 nodes are available: Insufficient cpu” The scheduler cannot find a node with enough unreserved CPU for the pod's request. Compare the request with node allocatable resources, then… Advanced · Fix · Linux Article Troubleshooting · Workloads & services 15 Oct 2026
0145 Fix: OOMKilled (exit code 137) in Kubernetes A container used more memory than its limit and the kernel killed it. Confirm the reason, measure real usage, then raise the… Advanced · Fix · Linux Article Troubleshooting · Workloads & services 15 Oct 2026
0160 Fix: Permission denied in a container on OpenShift because of the random UID A container that works under Docker or Kubernetes crashes on OpenShift with permission denied, because restricted-v2 runs it with a random non-root… Advanced · Fix · Linux Article Troubleshooting 15 Oct 2026
0161 Fix: Error from server (Forbidden): … is forbidden: User … cannot … in OpenShift oc refuses a command with Error from server (Forbidden). The message names the user, verb, resource and project. Learn how to read… Intermediate · Fix · Any system Article Cluster administration · Troubleshooting 15 Oct 2026
0167 Fix: Job for nginx.service failed because the control process exited with error code systemctl prints this when a service's start command exits with an error. The real reason is in journalctl; for nginx it is… Intermediate · Fix · Linux Article Networking & firewalls · Services & systemd 15 Oct 2026
0172 Fix: No space left on device Writes fail because a filesystem is full, out of inodes, or holding space for deleted files that are still open. Find which… Beginner · Fix · Linux Article Disks, LVM & filesystems 15 Oct 2026
0186 Fix: Ansible UNREACHABLE! Failed to connect to the host via ssh Ansible could not open an SSH session to the host, so no task ran. The text after the colon tells you why:… Intermediate · Fix · Linux, macOS Article Ansible · SSH & servers 15 Oct 2026
0190 Fix: Terraform Error acquiring the state lock Another run holds the lock on your Terraform state, or a crashed run left it behind. Find out who holds it, wait… Advanced · Fix · Any system Article Terraform 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 · Fix · 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 · Fix · Linux Article Install & connect · Security & access 15 Oct 2026
0211 Fix: psql connection to server on socket /var/run/postgresql/.s.PGSQL.5432 failed psql tried the local Unix socket and found nothing there. The server is not running, listens on another port, or uses a… Beginner · Fix · Linux Article Install & connect 15 Oct 2026
0220 Fix: ERROR 1045 (28000): Access denied for user ‘appuser’@’localhost’ (using password: YES) The server rejected the user, host and password combination. Usually it is a wrong password, a host part that does not match,… Beginner · Fix · Linux Article Administration · 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 · Fix · 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 · Fix · Any system Article Administration · Security & access 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 · Fix · Linux, macOS, Windows Article Administration · Basics 15 Oct 2026
0239 Fix: (error) NOAUTH Authentication required. (and securing Redis with ACLs) Redis requires a login and your client sent a command without one. Pass the right user and password, and use the moment… Advanced · Fix · Linux Article Administration & persistence · Security & access 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 · Fix · Linux Article Administration & persistence 15 Oct 2026