OhSudo — new articlesPractical articles for DevOps engineers, SysAdmins and IT folks.https://ohsudo.com/en-us"Address already in use": find who is using port 80 (or any port)https://ohsudo.com/articles/address-already-in-use-port-80/https://ohsudo.com/articles/address-already-in-use-port-80/Fix "bind() failed (98: Address already in use)": find the process holding the port with ss or lsof, then stop it, move it, or change your port.Sun, 01 Nov 2026 00:00:00 GMTNetworkingportsnginxapachesslsofsystemdtroubleshootingcontact@ohsudo.com (OhSudo)Docker "exited with code 137": OOM kill or a stop that took too longhttps://ohsudo.com/articles/docker-container-exited-with-code-137/https://ohsudo.com/articles/docker-container-exited-with-code-137/Exit code 137 means the container was killed with SIGKILL. Find out if it ran out of memory or ignored docker stop, and fix each case.Sun, 01 Nov 2026 00:00:00 GMTDocker & Containersdockerdocker-composeoommemorysignalstroubleshootingcontact@ohsudo.com (OhSudo)Kubernetes CrashLoopBackOff: 7 causes and how to find yourshttps://ohsudo.com/articles/kubernetes-crashloopbackoff/https://ohsudo.com/articles/kubernetes-crashloopbackoff/CrashLoopBackOff means the container keeps exiting. Read the exit code and the previous logs, then fix the crash, OOM kill, probe or command.Sun, 01 Nov 2026 00:00:00 GMTKuberneteskuberneteskubectlpodscrashloopbackoffprobestroubleshootingcontact@ohsudo.com (OhSudo)MySQL ERROR 1045 (28000): Access denied for user — find which part is wronghttps://ohsudo.com/articles/mysql-error-1045-access-denied/https://ohsudo.com/articles/mysql-error-1045-access-denied/Fix MySQL "ERROR 1045 Access denied for user": check the user@host account, the password, socket vs TCP, option files, and Docker init passwords.Sun, 01 Nov 2026 00:00:00 GMTDatabasesmysqlmariadbauthenticationusersdockertroubleshootingcontact@ohsudo.com (OhSudo)Nginx "502 Bad Gateway": find the cause in the error loghttps://ohsudo.com/articles/nginx-502-bad-gateway/https://ohsudo.com/articles/nginx-502-bad-gateway/Fix nginx 502 Bad Gateway: read error.log, then fix the backend that is down, the wrong address or socket, the crashing app, or SELinux on RHEL.Sun, 01 Nov 2026 00:00:00 GMTNetworkingnginxreverse-proxy502systemdselinuxtroubleshootingcontact@ohsudo.com (OhSudo)No space left on device: find what is filling your Linux diskhttps://ohsudo.com/articles/no-space-left-on-device/https://ohsudo.com/articles/no-space-left-on-device/Fix "No space left on device" on Linux: find the biggest directories and files, free space safely, and handle the cases where df says there is space.Sun, 01 Nov 2026 00:00:00 GMTLinuxdisk-spacedfdufindtroubleshootingcontact@ohsudo.com (OhSudo)"Permission denied" when running a script: 5 causes and fixeshttps://ohsudo.com/articles/permission-denied-running-script/https://ohsudo.com/articles/permission-denied-running-script/Fix "bash: ./script.sh: Permission denied" and "bad interpreter" on Linux: execute bits, noexec mounts, directory permissions, Windows line endings and shebangs.Sun, 01 Nov 2026 00:00:00 GMTLinuxbashpermissionschmodscriptstroubleshootingcontact@ohsudo.com (OhSudo)PostgreSQL "duplicate key value violates unique constraint": causes and fixeshttps://ohsudo.com/articles/postgresql-duplicate-key-value-violates-unique-constraint/https://ohsudo.com/articles/postgresql-duplicate-key-value-violates-unique-constraint/Fix "duplicate key value violates unique constraint" in PostgreSQL: tell a real duplicate from a sequence that is out of sync, and fix both safely.Sun, 01 Nov 2026 00:00:00 GMTDatabasespostgresqlsequencesunique-constraintupserttroubleshootingcontact@ohsudo.com (OhSudo)PostgreSQL "permission denied for table": causes and fixeshttps://ohsudo.com/articles/postgresql-permission-denied-for-table/https://ohsudo.com/articles/postgresql-permission-denied-for-table/Fix "ERROR: permission denied for table" in PostgreSQL: check what a role can do, grant the right privileges, and fix the schema, sequence and future-table cases.Sun, 01 Nov 2026 00:00:00 GMTDatabasespostgresqlpermissionsgranttroubleshootingcontact@ohsudo.com (OhSudo)SSH "Permission denied (publickey)": how to find the real causehttps://ohsudo.com/articles/ssh-permission-denied-publickey/https://ohsudo.com/articles/ssh-permission-denied-publickey/Fix SSH "Permission denied (publickey)": read the server log, fix ~/.ssh permissions, check the key and sshd_config, and handle SELinux on RHEL.Sun, 01 Nov 2026 00:00:00 GMTLinuxsshopensshkeyspermissionstroubleshootingcontact@ohsudo.com (OhSudo)