Linux Quick Reference Guide - crans.org

1 LinuxQuick Reference Guide8th edition January 2020 ForewordThis Guide stems from the notes I have been taking while studying and working as a Linux sysadmin and contains useful information about standards and tools for Linux system administration, as well as a good amount of topics from the certification exams LPIC-1 ( Linux Professional Institute Certification level 1), LPIC-2, RHCSA (Red Hat Certified System Administrator), and RHCE (Red Hat Certified Engineer). Unless otherwise specified, the shell of Reference is is an independent publication and is not affiliated with LPI or Red Hat.

2 You can freely use and share the whole Guide or the single pages, provided that you distribute them unmodified and not for document has been composed with Apache Linux hacking,Daniele RaffoVersion history1st edition2nd edition3rd edition4th edition5th edition6th edition7th edition8th editionMay 2013 September 2014 July 2015 June 2016 September 2017 August 2018 May 2019 January 2020 Bibliography and suggested readings Evi Nemeth et al., UNIX and Linux System Administration Handbook, O'Reilly Rebecca Thomas et al., advanced Programmer's Guide to Unix System V, McGraw-Hill Mendel Cooper, advanced bash - scripting Guide , Adam Haeder et al.

3 , LPI Linux Certification in a Nutshell, O'Reilly Heinrich W. Kl pping et al., The LPIC-2 Exam Prep, Michael Jang, RHCSA/RHCE Red Hat Linux Certification Study Guide , McGraw-Hill Asghar Ghori, RHCSA & RHCE RHEL 7: Training and Exam Preparation Guide , Lightning Source Inc. Colin Barschel, Unix Toolbox, Ellen Siever et al., Linux in a Nutshell, O'Reilly, Christoph Braun, Unix System Security Essentials, Addison-Wesley Bruce Barnett, The Grymoire, Brendan Gregg, Linux performance, Linus Torvalds' Linux documentation, RHEL manuals, A-Z index of bash command line, GNU software manuals, Shell command line snippets, bash command line snippets, RAM management in Linux , Regular expressions tester, bash pitfalls, Linux man pages, CentOS 7 man pages, startup service service Hierarchy and , ReiserFS.

4 CD-ROM 2 2 and text and system keysim and and POP IMAP mailbox POP/IMAP configuration configuration Hat vs Debian network and NAT bindings - bindings - X compile and zone response server main virtual global share access Hat Satellite search and ASCII Volume Management (LVM) introduces an abstraction between physical and logical storage, allowing a more versatileuse of filesystems. LVM uses the Linux device mapper feature (/dev/mapper).

5 Disks, partitions, and RAID devices are made of Physical Volumes, which are grouped into a Volume Volume Group is divided into small fixed-size chunks called Physical Extents, which are mapped 1-to-1 to Logical Extents. Logical Extents are grouped into Logical Volumes, on which filesystems are created. How to create a Logical a new disk to the that the new disk is recognized as / /dev/sdaCreate a new partition (of type 0x8E = Linux LVM) on the new disk. This is not necessary but recommended, because other OSes might not recognize the LVM header and see the whole unpartitioned disk as /dev/sda1 Initialize the Physical Volume to be used with -s 8M myvg0 /dev/sda1 Create a Volume Group and define the size of Physical Extents to 8 Mb (default value is 4 Mb)

6 Orvgextend myvg0 /dev/sda1or add the Physical Volume to an existing Volume -L 1024M -n mylv myvg0 Create a Logical -t ext3 /dev/myvg0/mylvCreate a filesystem on the Logical /dev/myvg0/mylv /mnt/mystuffMount the Logical VolumeHow to increase the size of a Logical Volume (operation possible only if the underlying filesystem allows it) a new disk to the machine, to provide the extra disk space /dev/sdcInitialize the Physical Volume myvg0 /dev/sdcAdd the Physical Volume to an existing Volume the size of an existing disk (already initialized as PV) the kernel of the new disk /dev/sdcAccommodate the Physical Volume to the new size -L 2048M /dev/myvg0/mylvExtend the Logical Volume by 2 Gborlvresize -L+2048M /dev/myvg0/mylvorlvresize -l+100%FREE /dev/myvg/mylvor extend the Logical Volume taking all free space /dev/myvg0/mylv (ext)xfs_growfs /dev/myvg0/mylv (XFS)Extend the , use lvresize -r on the previous stepHow to reduce the size of a Logical Volume (operation possible only if the underlying filesystem allows it)

7 /dev/myvg0/mylv 900 MShrink the filesystem to 900 -L 900M /dev/myvg0/mylvShrink the Logical Volume to 900 Mborlvresize -L 900M /dev/myvg0/mylvHow to snapshot and backup a Logical -s -L 1024M -n mysnap /dev/myvg0/mylvCreate the snapshot like a Logical cvzf mysnap Backup the snapshot with any backup /dev/mvvg0/mysnapDelete the snapshotLinux Quick Reference Guide 8th ed., Jan 2020 Daniele Raffo ~raffo2/189 LVM commandsLVM commandsPV commandsVG commandsLV commandspvsReport information aboutPhysical VolumesvgsReport information about Volume GroupslvsReport information about Logical VolumespvscanScan all disks for Physical VolumesvgscanScan all disks for Volume GroupslvscanScan all disks for Logical VolumespvdisplayDisplay Physical Volume attributesvgdisplayDisplay Volume Group attributeslvdisplayDisplay Logical Volume attributespvckCheck Physical Volume metadatavgckCheck Volume Group metadatapvcreateInitialize a disk or partition for use with

8 LVMvgcreateCreate a Volume Groupusing Physical VolumeslvcreateCreate a Logical Volume in a Volume GrouppvchangeChange Physical Volume attributesvgchangeChange Volume Group attributeslvchangeChange Logical Volume attributespvremoveRemove a Physical VolumevgremoveRemove a Volume GrouplvremoveRemove a Logical VolumevgextendAdd a Physical Volume to a Volume GrouplvextendIncrease the size of a Logical Volumevgreduce Remove a Physical Volume from a Volume GrouplvreduceShrink the size a Logical VolumepvresizeModify the size of a Physical VolumelvresizeModify the size of a Logical VolumevgmergeMerge two Volume GroupsvgsplitSplit two Volume GroupsvgimportImport a Volume Groupinto a systemvgexportExport a Volume Group from a system pvmove Move the Logical Extentson a Physical Volume to wherever there are available Physical Extents (within the Volume Group) and thenput the Physical Volume offline LVM global commandsdmsetup commandPerform low-level LVM operationslvm commandPerform LVM operations.

9 May also be used as an interactive toollvmsarLVM system activity reporter. Unsupported on LVM2lvmdiskscanScan the system for disks and partitions usable by LVMlvmconfigShow the current LVM disk configuration/dev/mapper/vgname-lvname/d ev/vgname/lvnameMapping of Logical Volumes in the filesystem/etc/lvm/archive/ Directory containing Volume Groups metadata backupsLinux Quick Reference Guide 8th ed., Jan 2020 Daniele Raffo ~raffo3/189 System bootSystem bootBoot sequencePOST(Power-On Self Test)Low-level check of PC (Basic I/O System)Detection of disks and loaderGRUB(GRand UnifiedBootloader)GRUB stage 1 is loaded from the MBR and executes GRUB stage 2 from filesystem.

10 GRUB chooses which OS to boot chain loader hands over to the boot sector of the partition on which resides the chain loader also mounts initrd, an initial ramdisk (typically a compressed ext2 filesystem) to be used as the initial root device during kernel boot; this make possible to load kernel modules that recognize hard drives hardware and that are hence needed to mount the real root filesystem. Afterwards, the system runs /linuxrc with PID 1.(From Linux onwards, the system instead loads into memory initramfs, a cpio-compressed image, and unpacks it into an instance of tmpfs in RAM.)