Linux
Linux commands, diagnostics and resources for Debian, Ubuntu, Bash, systemd, SSH, files, network, logs and backups
Linux / Debian Center
Linux/Debian diagnostic: systemd, boot, network, DNS, SSH, disk, apt/dpkg, memory, logs, permissions, NTP,19th and Docker
Command / scriptList failed systemd services
Displays the currently systemd units in state
Command / scriptShow Linux disk space and filesystems
Displays volumes mounted with their size, space used, space available and occupancy rates
Command / scriptIdentify large folders under Linux
Classifies the main root files according to their size to find the source of saturation
Command / scriptList listening ports on Linux
Displays the Twitter and UDP listening as well as associated processes
Knowledge hubIT Cheat Sheets
Printable memo sheets for PowerShell, Windows, DNS, SMTP, Active Directory, FortiGate, Linux, VMware, M365 and Robocopy.
Knowledge hubHome
Free tools, procedures, diagnostics, scripts, dictionary and practical resources for IT technicians, system administrators and SMEs
IT dictionarySSH Jump Host
An SSH jump host is an intermediate system used to reach otherwise inaccessible machines securely.
IT dictionarySSH Forwarding
SSH forwarding securely transports selected local, remote, or dynamic TCP connections through an encrypted SSH session.
IT dictionarySSH Host Key
An SSH host key identifies the remote SSH server and helps clients detect connection interception.
IT dictionarySSH ControlMaster
SSH ControlMaster allows multiple SSH sessions to reuse one authenticated network connection.
IT dictionaryKerberos Client Linux
A Linux Kerberos client obtains and uses tickets to authenticate to services within a Kerberos realm.
IT dictionaryNSS Linux
Linux Name Service Switch controls how applications resolve user, group, host, and other identity data.
ResourceHow to check the disk space of, Linux server
Quickly display l, use file systems on Linux
ResourceHow to find what fills a Linux drive
It is necessary to distinguish space saturation, saturation in inodes and deleted files still open before cleaning a Linux server
ResourceHow to diagnose a systemd timer
This BOAI guide provides a structured method for diagnosing a systemd timer without multiplying unnecessary changes
ResourceHow to scan a systemd service that does not start
systemctl gives the immediate state of the service while journalctl often explains why the main process has stopped
ResourceHow to diagnose a Linux filesystem read-only
Reading-only editing can be a protective measure after a storage error or filesystem
Resourcesystemd — Start request repeated too quickly
systemd stopped restarting a service after several rapid failures
Troubleshootingsystemd timer does not trigger
A task planned via systemd does not run at the expected time
ResourceLinux — No spaceleft on device
Linux cannot write to the target filesystem because capacity, inodes or a storage quota have been exhausted.
TroubleshootingDocker volume fills the Linux disk
A container volume or log gradually consumes the entire filesystem
TroubleshootingFilesystem Linux passed read-only
The file system is mounted read-only and the scripts fail
ResourceTCP vs UDP: What Is the Difference?
TITLE focuses on reliability and data order. UDP focuses on simplicity and speed, without guaranteeing delivery
ProcedureSet up a systemd timer
Controlled procedure to set up a systemd timer
ProcedureHandle a saturated Linux filesystem without risky deletion
Procedure to find the cause of a full filesystem before cleaning
ProcedureSet up an immutable backup repository
Plan a Veeam Linux hardened repository, validate product-managed immutability and restricted administration, then prove recovery using an isolated restore.
ProcedureHandle a VMware VM with an inconsistent snapshot chain
Secure the VM and analyze descriptors when a parent of the company is missing or disabled
ProcedureImplement a 3-2-1 backup strategy
Design multiple copies, on separate media, with at least one external or isolated copy
ProcedureSecure a compromised WordPress site
Keep it up, incident, preserve the evidence, clean the files and prevent a new Emma
ResourceLinux — Essential commands
Linux commands for services, logs, processes, storage, networking, DNS, permissions and system diagnostics.
ResourceDNS — memo form
DNS record types, resolver checks, delegation, caching and commands for diagnosing name resolution.
ResourceNetwork ports — memo form
Common TCP and UDP ports, their services and practical checks for network administration.
Knowledge hubIT Networking
Tools and methods for DNS, DHCP, VLAN, routing, Wi-Fi, LINK, TITLE/IP, latency, MTU and network diagnostics
Knowledge hubBackup & Disaster Recovery
Backup, restoration and resumption of activity: Veeam, Acronis, VSS, RPO, RTO, immutability, replication and restoration tests.
Knowledge hubCybersecurity
Defensive resources for phishing, ransomware, compromised accounts, MFA, hardening,19th, incidents and protection of backups
Knowledge hubProxmox VE
Proxmox VE administration and troubleshooting: nodes, QEMU VM, LXC, Cluster, Ceph containers, storage, backups, migration and network
Knowledge hubSQL / Databases
SQL Server, MySQL, MariaDB and PostgreSQL administration and troubleshooting: connections, performance, blocking, backups, logs and storage