Linux
35 sheets
- LinuxQuick reference for everyday Linux administration. Topic-specific sheets: Linux Basics, User Management, Grep, SED Cheat-Sheet, AWK, Mount, NFS, UFW…
- AWKAWK (awk) is a domain-specific language designed for text processing and typically used as a data extraction and reporting tool. Similar to the Sed and Grep…
- BtrfsBtrfs is a copy-on-write Linux filesystem with built-in subvolumes, snapshots, checksums, compression, multi-device RAID profiles and send/receive replication…
- CephCeph is a distributed storage system that provides block (RBD), file (CephFS) and object (RGW) storage from commodity servers, with data replicated across…
- chronychrony is the NTP client and server used on most modern Linux distributions to keep the clock accurate. Correct time matters for TLS certificates, Kerberos…
- Disk UsageFind out what is filling a disk with df, du, ncdu and lsof. Start with df to see which filesystem is full, then du or ncdu to find the directory, and check for…
- ethtoolethtool queries and changes the settings of Ethernet network interfaces: link speed and duplex, offloads, ring buffers, driver details and Wake-on-LAN. Use it…
- firewalldfirewalld is the default firewall manager on Fedora, RHEL and derivatives. It groups interfaces and sources into zones, allows traffic by service or port, and…
- GrepGrep is a command-line utility for searching plain-text data for lines matching a regular expression. Its name comes from the ed command g/re/p (globally…
- Hardware InspectionList the PCI and USB devices, CPU, memory, disks and firmware details of a Linux machine with lspci, lsusb, lshw, dmidecode and friends. Use it to identify a…
- ip and ssip (from iproute2) shows and changes interfaces, addresses, routes and the neighbour (ARP) table; ss lists sockets and replaces netstat. Both are on every…
- IPTablesIptables is a user-space utility program that allows a system administrator to configure the IP packet filter rules of the Linux kernel firewall, implemented…
- journalctljournalctl reads the systemd journal, the log store behind systemd services and the kernel. Use it to follow a service, find what happened before a crash or…
- libvirt and KVMKVM is the Linux kernel hypervisor and QEMU the emulator that runs the guests. libvirt is the management layer on top: virsh is its shell, virt-install creates…
- Linux BasicsNetwork and host configuration on Ubuntu. For everyday commands see Linux.
- Linux Performance TroubleshootingA short path from "the server is slow" to the resource that is the cause. Start with the USE method (utilisation, saturation, errors for each resource), then…
- logrotatelogrotate rotates, compresses and removes old log files on a schedule or when they reach a size. On Debian and Ubuntu it is run daily by a systemd timer or…
- LVMThe Logical Volume Manager adds a layer between disks and file systems. Physical volumes (PV) are pooled into volume groups (VG), and logical volumes (LV) are…
- mergerfsmergerfs is a FUSE union filesystem that presents several disks or directories as one mount point, while each disk keeps its own filesystem and can be read on…
- MountIn Linux, mount attaches a filesystem on a device to a directory. Before a user can access a file on a Unix-like machine, the filesystem on the device which…
- NetplanNetplan is the network configuration layer on Ubuntu: YAML files in /etc/netplan/ are rendered into configuration for systemd-networkd or NetworkManager. Use…
- NFSNetwork File System (NFS) is a distributed file system protocol originally developed by Sun Microsystems (Sun), available in Linux, allowing a user on a client…
- nftablesnftables is the modern Linux packet filter and the successor to iptables, ip6tables, arptables and ebtables. One tool (nft) and one syntax cover IPv4, IPv6…
- RAID with mdadmmdadm manages Linux software RAID (the md driver). It builds arrays from whole disks or partitions, watches their health and rebuilds after a disk fails. RAID…
- SED Cheat-Sheetsed ("stream editor") is a Linux and Unix utility that parses and transforms text using a compact programming language. See also Grep and Awk.
- SELinux and AppArmorTwo Linux Mandatory Access Control systems. SELinux (RHEL, Fedora, Rocky, Alma) labels every file and process and applies a policy. AppArmor (Ubuntu, Debian…
- smartctlsmartctl (from smartmontools) reads and tests a disk's SMART data, and smartd watches it in the background and emails or notifies you. Use it to catch a…
- SnapRAIDSnapRAID is a snapshot parity tool for arrays of mostly static files, such as media libraries. Data disks stay independent filesystems, one or more parity…
- Storage and FilesystemsPartitioning, creating file systems, checking disk health and measuring disk speed on Linux. Mounting is covered in Mount; volume management in LVM and…
- systemdsystemd is the init system and service manager on nearly every modern Linux distribution. It starts services, runs timers, collects logs (journald) and applies…
- tunedtuned is a daemon that applies system tuning profiles (CPU governor, sysctl, disk and network settings) on Linux. It is standard on RHEL and Fedora and also…
- UFW (uncomplicated firewall)UFW (uncomplicated firewall) is a firewall configuration tool for Linux that runs on top of IPTables, included by default within Ubuntu distributions. It…
- User ManagementCreate, change and remove users and groups, set up sudo and SSH keys, and inspect logins. Debian/Ubuntu adduser is a friendlier wrapper around the lower-level…
- XFSXFS is a high-performance journalling file system, the default on RHEL and its derivatives and common for large volumes and media storage. It grows online but…
- ZFSZFS is a combined filesystem and volume manager: disks are grouped into pools (zpool), and datasets and volumes (zfs) are carved out of them with checksumming…