Articles

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52 entries match these filters

0413 Fix: 502 Bad Gateway from Nginx Nginx is running but could not get a valid response from your application. Read the error log, check that the app is… Intermediate · Fixes an error · Linux Article Web servers & reverse proxies 15 Oct 2026
0423 Fix: bad interpreter or command not found after a script is copied from Windows (CRLF) A script edited on Windows carries invisible carriage returns, so Linux looks for /bin/bash^M. How to spot CRLF line endings, convert them… Beginner · Fixes an error · Linux, macOS, Windows Article Basics · Shell scripting 15 Oct 2026
0375 Fix: disk full, find what is eating the space A Linux filesystem reports 100 percent used or No space left on device. Find the culprit with df and du, check journals,… Intermediate · Fixes an error · Linux Article Alerting & dashboards · Disks, LVM & filesystems 15 Oct 2026
0382 Fix: Resource not accessible by integration and other GitHub Actions permission errors A workflow step fails with Resource not accessible by integration, 403 on git push, or a GitHub CLI call is refused. The… Intermediate · Fixes an error · Any system Article GitHub Actions 15 Oct 2026
0320 Fix: address already in use (EADDRINUSE) Something is already listening on the port your program wants. Find the process with lsof or ss, stop it or pick another… Beginner · Fixes an error · Linux, macOS Article Networking & firewalls · Node.js · Processes & ports 15 Oct 2026
0321 Fix: E: Unable to locate package / could not get lock /var/lib/dpkg/lock Two apt errors with simple causes: Unable to locate package means the package lists are stale or the name is wrong; could… Beginner · Fixes an error · Linux Article Packages & updates 15 Oct 2026
0322 Fix: user is not in the sudoers file sudo refuses because your account is not allowed to use it. Add the user to the sudo group (Debian, Ubuntu) or wheel… Beginner · Fixes an error · Linux, macOS Article Server hardening · Users, sudo & hardening 15 Oct 2026
0323 Fix: Failed to start service, how to read systemctl status and journalctl Job for x.service failed tells you only that the service did not start. The real reason is in systemctl status and journalctl… Beginner · Fixes an error · Linux Article Logs · Services & systemd 15 Oct 2026
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
0325 Fix: SSL certificate problem: unable to get local issuer certificate curl, git, pip or npm cannot chain the server's certificate to a root they trust. Usual causes: a corporate proxy that re-signs… Intermediate · Fixes an error · Linux, macOS, Windows Article Common errors · Making requests · TLS & certificates 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
0333 Fix: permission denied while trying to connect to the Docker daemon socket Every docker command fails with permission denied on /var/run/docker.sock. The daemon is fine; your user is not allowed to use its socket.… Beginner · Fixes an error · Linux Article Docker basics · Docker fixes 15 Oct 2026
0334 Fix: port is already allocated docker run or docker compose up fails with Bind for 0.0.0.0:8080 failed: port is already allocated. Find what holds the port, another… Beginner · Fixes an error · Linux, macOS, Windows Article Docker fixes · Processes & ports 15 Oct 2026
0343 Fix: Connection refused and Connection timed out, what each one means Refused means the host answered and nothing is listening there. Timed out means no answer at all, usually a firewall or wrong… Beginner · Fixes an error · Linux, macOS Article DNS, IP addresses & ports · Firewalls 15 Oct 2026
0316 Fix: command not found bash: something: command not found means the shell could not find a program with that name in any PATH directory. The usual… Beginner · Fixes an error · Linux, macOS Article Basics · Packages & updates 15 Oct 2026
0317 Fix: Permission denied when running a script (chmod +x) bash: ./script.sh: Permission denied means the file exists but you may not execute it. Usually the execute bit is missing; sometimes the… Beginner · Fixes an error · Linux, macOS Article Basics · Users, sudo & hardening 15 Oct 2026
0318 Fix: fatal: not a git repository Git looked in the current directory and every parent for a .git folder and found none. You are in the wrong directory,… Beginner · Fixes an error · Any system Article Common errors · Setup 15 Oct 2026
0319 Fix: npm ERR! EACCES permission denied npm cannot write to a directory it needs: the global install location, its cache in ~/.npm, or a node_modules owned by root.… Beginner · Fixes an error · Linux, macOS Article Common errors · Node.js 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
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 · Fixes an error · 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 · 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
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 · Fixes an error · 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 · Fixes an error · 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 · 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
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 · Fixes an error · 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 · Fixes an error · 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 · Fixes an error · Any system Article Terraform 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 · Fixes an error · 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 · Fixes an error · 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 · Fixes an error · 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 · Fixes an error · 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 · Fixes an error · 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 · Fixes an error · 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 · Fixes an error · Linux Article Networking & firewalls · Services & systemd 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 · Fixes an error · 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 · Fixes an error · 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 · Fixes an error · Linux Article Clusters & high availability 15 Oct 2026