(RHCSA) Create and Configure File Systems

This is part of the independent and unofficial RHCSA Exam Study Guide series providing free 🤑 resources to prepare for the exam.

This post covers the objectives under the section:

“CREATE AND CONFIGURE FILE SYSTEMS”

It contains two main parts:

• Resources: with links to learn and practice for each objective.
• Cheatsheet: containing some examples of commands and actions performed in each objective (when applied).

📚 Resources:

CREATE, MOUNT, UNMOUNT, AND USE VFAT, EXT4, AND XFS FILE SYSTEMS

• 📌 RHCSA v8 Practice Session: Create, mount, unmount, and use vfat, ext4, and xfs file systems

• 📌 How to create and mount filesystems in Linux

MOUNT AND UNMOUNT NETWORK FILE SYSTEMS USING NFS

• 📌 RHCSA v8 Practice Session: Mount and unmount network file systems using NFS

• 📌 Linux Server Administration - Network File System (NFS) Overview

• 📌 Learning NFS through server and client configuration

• 📌 Mount NFS filesystems with autofs

• 📌 Chapter 18. Mounting file systems on demand

EXTEND EXISTING LOGICAL VOLUMES

• 📌 RHCSA v8 Practice Session: Extend existing logical volumes

• 📌 Logical Volume Manager (LVM) versus standard partitioning in Linux

• 📌 Chapter 5. Modifying the size of a logical volume

• 📌 How to resize a logical volume with 5 simple LVM commands

• 📌 6.3. Resizing an Ext4 File System

CREATE AND CONFIGURE SET-GID DIRECTORIES FOR COLLABORATION

• 📌 RHCSA v8 Practice Session: Create and configure set-GID directories for collaboration

• 📌 Special File Permissions in Linux: SUID, GUID and Sticky Bit

• 📌 Linux permissions: SUID, SGID, and sticky bit

• 📌 Create and configure setgid directories for collaboration – RHCSA Objective Preparation

CONFIGURE DISK COMPRESSION

• 📌 RHCSA v8 Practice Session: Configure disk compression

• 📌 Tuesday Tech Tip - Virtual Data Optimizer Part 1

• 📌 A look at VDO, the new Linux compression layer

• 📌 Chapter 1. Deploying VDO

• 📌 What is VDO? Virtual Data Optimizer storage explained - RHCSA 8 Prep by Sander van Vugt

MANAGE LAYERED STORAGE

• 📌 RHCSA v8 Practice Session: Manage layered storage

• 📌 How To Manage Layered Local Storage With Stratis On RHEL 8

• 📌 RHEL 8 Beta - Managing Storage With Stratis

• 📌 23.1. Setting up Stratis file systems (skip items: from 23.1.6 to 23.1.11)

• 📌 23.2. Extending a Stratis volume with additional block devices

• 📌 23.3. Monitoring Stratis file systems

• 📌 23.4. Using snapshots on Stratis file systems

• 📌 23.5. Removing Stratis file systems

DIAGNOSE AND CORRECT FILE PERMISSION PROBLEMS

(This objective is also covered in: “understand and use essential tools / list, set, and change standard ugo/rwx permissions” and “manage security / create and use file access control lists”)

• 📌 RHCSA v8 Practice Session: Diagnose and correct file permission problems

• 📌 An introduction to Linux Access Control Lists (ACLs)

📑 Cheatsheet:

CREATE, MOUNT, UNMOUNT, AND USE VFAT, EXT4, AND XFS FILE SYSTEMS

• mkfs.ext4 /dev/sdb1 ➡ create an ext4 file system in /dev/sdb1 partition.

• mount /dev/sdb1 /test ➡ mount /dev/sdb1 file system at /test mountpoint (won’t survive a system reboot).

• unmount /dev/sdb1 ➡ unmount /dev/sdb1 filse system.

• On /etc/fstab add /dev/sdb1 /test ext4 defaults 0 0 ➡ to mount the file system on system startup.

• mount -a ➡ mount all filesystems mentioned in /etc/fstab.

MOUNT AND UNMOUNT NETWORK FILE SYSTEMS USING NFS

(Requires nfs-utils and autofs packages)

• Setup NFS server (to serve a directory):

  • chmod 755 /common ➡ add full permissions to dir, before sharing.
  • firewall-cmd --permanent --add-service nfs & firewall-cmd --reload ➡ allow NFS traffic to pass through firewalld.
  • systemctl --now enable nfs-server ➡ enable NFS server.
  • On /etc/exports file add: /common/ 192.168.0.110(rw)
  • exportfs -av ➡ export or unexport all items on /etc/exports (verbose mode).

• exportfs -u 192.168.0.110:/common ➡ unexport dir.

• Mount share on NFS client (old way to mount):

  • mkdir /local
  • mount 192.168.0.120:/common /local ➡ to mount manually.
  • On /etc/fstab add: 192.168.0.120:/common /local nfs _netdev 0 0 ➡ to mount on system startup.
  • mount | grep local ➡ to confirm mounting success.

• Mount share on client on-demand using AutoFS (preferred way to mount):

  (If using AutoFS for a sharing, do not mount manually or via /etc/fstab!)

  • USING DIRECT MAP

    • mkdir /autodir
    • On /etc/auto.master add /- /etc/auto.master.d/auto.dir ➡ to create the mapping.
    • Create /etc/auto.master.d/auto.dir file and add /autodir 192.168.0.120:/common ➡ to automount the shared fs on /autodir.

  • USING INDIRECT MAP (preferred way)

    • On /etc/auto.master add /autoindir /etc/auto.master.d/auto.indir ➡ to create the indirect mapping.
    • Create /etc/auto.master.d/auto.indir file and add common 192.168.0.120:/common ➡ to automount the shared fs on /autodir(name the mountpoint just like the shared folder’s name).
    • systemctl enable --now autofs or systemctl restart autofs ➡ to start.

EXTEND EXISTING LOGICAL VOLUMES

• vgextend vg100 /dev/vdc ➡ extend volume gropup adding a new physical volume.

• lvextend -L +200M /dev/vg100/lvol0 ➡ expand logical volume size.

• lvextend -r -L +80M /dev/vg200/lv200 ➡ extend local volume and its file system.

• resize2fs /dev/vg200/lv200 3T ➡ resize ext4 file system.

• xfs_growfs /dev/vg200/lv200 ➡ resize xfs file system.

CREATE AND CONFIGURE SET-GID DIRECTORIES FOR COLLABORATION

• chmod +2000 /usr/bin/write, chmod g+s /usr/bin/write ➡ enables setgid in write file without touching other predefined permissions.

• chmod +1000 /tmp, chmod o+t /tmp ➡ sets the sticky bit on the specified directory without altering existing underlying permissions. (sticky bit on public and shared writable dirs are used to protect files and subdirs owned by normal users from being deleted or moved by other normal users.)

CONFIGURE DISK COMPRESSION

(If kernel update was previously installed from file, you might need to download and install vdo and kmod-kvdo from file too.)

• vdo list, vdostats, lsblk ➡ see vdo volumes.

• vdo create --name=testvdo --device=/dev/vdh --vdoLogicalSize=16G --vdoSlabSize=128M ➡ create new vdo volume named testvdo with logical size of 16GB and slab size of 128mb.

• vdo status --name testvdo | grep -i dupl ➡ check if vdo volume has deduplication enabled.

• mkfs.xfs -K /dev/mapper/vdo-name ➡ create xfs filesystem on vdo volume.

• mkfs.ext4 -E nodiscard /dev/mapper/vdo-name ➡ create ext4 filesystem on vdo volume, avoid discarding blocks.

• On /etc/fstab add /dev/mapper/vdo-name mount-point xfs defaults,x-systemd.device-timeout=0,x-systemd.requires=vdo.service 0 0 to mount the xfs file system.

• On /etc/fstab add /dev/mapper/vdo-name mount-point ext4 defaults,x-systemd.device-timeout=0,x-systemd.requires=vdo.service 0 0 to mount the ext4 file system.

• vdo disableCompression --name testvdo ➡ disable compression to vdo volume.

MANAGE LAYERED STORAGE

(Requires stratisd and stratis-cli packages)

• systemctl enable --now stratisd ➡ Start Stratis service.

• stratis pool create strpool /dev/vdg ➡ create strpool stratis pool using /dev/vdg block device.

• stratis pool list ➡ list pools.

• stratis blockdev ➡ display information of block devices used by stratis.

• stratis fs ➡ display information of stratis filesystems.

• stratis pool add-data strpool /dev/vdh ➡ expand the stratis pool adding another block device.

• stratis fs snapshot my-pool my-fs my-fs-snapshot ➡ create a snapshot from my-fs stratis filesystem.

• mount /dev/stratis/my-pool/my-fs mount-point ➡ mount a stratis snapshot.

• stratis filesystem destroy my-pool my-fs-snapshot ➡ remove a stratis snapshot (you must unmount the snapshot first).

• stratis pool destroy strpool ➡ remove stratis pool.

• stratis filesystem create strpool5 strfs5 ➡ create strfs5 filesystem on strpool5 stratis pool.

• On /etc/fstab add UUID=a1f0b64a-4ebb-4d4e-9543-b1d79f600283 /fs1 xfs defaults,x-systemd.requires=stratisd.service 0 0 ➡ to mount a stratis file system (it must be identified by it’s UUID).

DIAGNOSE AND CORRECT FILE PERMISSION PROBLEMS

• chmod 644 somefile.txt ➡ set file permissions to u=rw,g=r,o=r.

• chmod +022 somefile.txt ➡ add g=w,o=w permissions to the file.

• chmod ug+x,o-w ➡ add user and group execute permission and remove write permission from others.

• chown root:sgrp /sdir ➡ change ownership and owning group to root and sgrp respectively.

• chmod +4000 /usr/bin/su, chmod u+s /usr/bin/su ➡ enables setuid in su file without touching other predefined permissions. (setuid is used to give special permissions on executable files)

• chmod +2000 /usr/bin/write, chmod g+s /usr/bin/write ➡ enables setgid in write file without touching other predefined permissions.

• chmod +1000 /tmp, chmod o+t /tmp ➡ sets the sticky bit on the specified directory without altering existing underlying permissions. (sticky bit on public and shared writable dirs are used to protect files and subdirs owned by normal users from being deleted or moved by other normal users.)

• chown user1:dba -R dir1 ➡ change dir1 owner to user1 and group to dba recursively (could change only group owning with chgrp too).

• setfacl -m u:user100:6 file1, setfacl -m u:user100:rw file1 ➡ gives user100 read and write permissions on file1 by using Access Control Lists (ACLs).

• setfacl -x u:user100 file1 ➡ removes any user100 ➡ ACL permissions for file1.

• setfacl -b file1 ➡ resets ACL permissions for file1.

• setfacl -dm u:user100:7,u:user200:rwx projects/ ➡ allocate default rwx permissions to user100 and user200 on projects/ dir.

• setfacl -k projects/ ➡ deletes default ACL permissions for projects/ directory.

Next:

(RHCSA) Deploy, Configure, and Maintain Systems

…or back to Red Hat Certified System Administrator (RHCSA) Exam Study Guide

Useful links & references:

• Red Hat Enterprise Linux Documentation

• Enable Sysadmin (a blog from Red Hat)

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