Difference between revisions of "NewLinuxInfo"

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There are hundreds if not thousands of file system tools, utilities and apps, so here I will try to go over the main, best, and most useful file system tools in my opinion.  This section will have to be a "work in progress", and I will add to this section as time permites, as I find myself needing to use these applilcations.
 
There are hundreds if not thousands of file system tools, utilities and apps, so here I will try to go over the main, best, and most useful file system tools in my opinion.  This section will have to be a "work in progress", and I will add to this section as time permites, as I find myself needing to use these applilcations.
 
<br /><br />
 
<br /><br />
 +
'''ALL of these tools and utilities must be ran as either the root superuser, or using the "sudo" prefix!'''
 +
 +
=== '''FDISK''' ===
 +
fdisk, the disk partitionling command-line tool, as are all Linux command line commands, Case Sensitive, and  therefore always lower case!  fdisk doesn't always need switches, but ALWAYS MUST have arguments!  In the case of fdisk, the most common switch is the "l" switch, a lower-case L.  It's used to only LIST, and NOT change/modify any disk partitions.  The "l" switch spits out the current partition pointed to with the argument, which is always a Linux "device" file, such as "/dev/sda", case sensitive, without the quotes.  /dev/sda is the first hard drive, with the "s" part referring to the old SCSI protocol.  Therefore, /dev/sda referres to SCSI device A, the first drive in a Linux system.  The next drive would be /dev/sdb, the third drive would be /dev/sdc, and so on.
 +
 +
On more modern systems, that don't use old-school hard drives, the newest technology drives used for storage, especially on laptops, are M.1 drives, which are solid-state drives which usually use the NVMe standard, making the device files for those drives something like /dev/nvme01p0, or similar.  CD & DVD writers(also referred to "burners"), often use "/dev/sr0" as the first CD/DVD burner on a system, which stand for "SCSI Recorder Number 0", since numbering usually starts with 0 on computer systems.
 +
 +
Regardless of the device files being used, the "fdisk" commands are all basically the same, other than the actual device you are partitionling, which is CRITICAl, as there is NO going back once you have partitioned and written that partion table to the drive!!! 
 +
Therefore, you MUST ALWAYS be 100% CERTAIN you are using the correct hard of solid-state drive file!!!
 +
 +
One more BIG concern to take into account is if the disk already has an existing partion table created, from being previously used, you MUST be sure to use the CORRECT disk partitioning tools, as newer, larger and more modern computers use the new disk partitioning tool called GDISK, instead of FDISK!  Both are used with all Lower Case letters(fdis & gdisk), but if there is already a "gdisk" partioned disk, known as a "GPT" partition table, you MUST use the "gdisk" tool to make any changes/modification to the disk's partition table, and visa versa in the case of a disk with an existing "fdisk" partion table, known as the "DOS" partition table type.  It usually shows as all lower-case, such as "dos".
 +
 +
Usesage of both partitioning tools are almost identicle, with the only real differences being the partition type hex-codes used to define the partition types at creation time.
 +
 +
The first step is the unmount the USB flash drive, before using any partitioning tools, as it can otherwise corrupt the drive. Because I am using an existing 256GB USB 3.0 flash drive, I prefer to use the udiskctl utility to both unmount and power-off USB flash drives.
 +
Here is the command I use to "unmount" the drive, before making any changes to it's partition table:
 +
<pre style="color:blue">
 +
[root@server.dawgland.com:~]# udisksctl unmount -b /dev/sdl
 +
Unmounted /dev/sdl.
 +
[root@server.dawgland.com:~]#
 +
</pre>
 +
 +
Next, I need to use the fdisk tool to delete the existing partitions on the USB flash drive:
 +
<pre style="color:blue">
 +
[root@server.dawgland.com:~]# fdisk /dev/sdl
 +
 +
Welcome to fdisk (util-linux 2.35.2).
 +
Changes will remain in memory only, until you decide to write them.
 +
Be careful before using the write command.
 +
 +
The device contains 'exfat' signature and it will be removed by a write command. See fdisk(8) man page and --wipe option for more details.
 +
 +
Command (m for help): p
 +
 +
Disk /dev/sdl: 234.38 GiB, 251658240000 bytes, 491520000 sectors
 +
Disk model: ProductCode   
 +
Units: sectors of 1 * 512 = 512 bytes
 +
Sector size (logical/physical): 512 bytes / 512 bytes
 +
I/O size (minimum/optimal): 512 bytes / 512 bytes
 +
Disklabel type: dos
 +
Disk identifier: 0x00000000
 +
 +
Device    Boot      Start        End    Sectors  Size Id Type
 +
/dev/sdl1      4294967295 8589934589 4294967295    2T ff BBT
 +
/dev/sdl2      4294967295 8589934589 4294967295    2T ff BBT
 +
/dev/sdl3      4294967295 8589934589 4294967295    2T ff BBT
 +
/dev/sdl4      4294967295 5035196669  740229375  353G ff BBT
 +
 +
Command (m for help): d
 +
Partition number (1-4, default 4):
 +
 +
Partition 4 has been deleted.
 +
 +
Command (m for help): d
 +
Partition number (1-3, default 3):
 +
 +
Partition 3 has been deleted.
 +
 +
Command (m for help): d
 +
Partition number (1,2, default 2):
 +
 +
Partition 2 has been deleted.
 +
 +
Command (m for help): d
 +
Selected partition 1
 +
Partition 1 has been deleted.
 +
 +
Command (m for help): p
 +
Disk /dev/sdl: 234.38 GiB, 251658240000 bytes, 491520000 sectors
 +
Disk model: ProductCode   
 +
Units: sectors of 1 * 512 = 512 bytes
 +
Sector size (logical/physical): 512 bytes / 512 bytes
 +
I/O size (minimum/optimal): 512 bytes / 512 bytes
 +
Disklabel type: dos
 +
Disk identifier: 0x00000000
 +
 +
Command (m for help): w
 +
The partition table has been altered.
 +
Calling ioctl() to re-read partition table.
 +
Syncing disks.
 +
 +
[root@server.dawgland.com:~]#
 +
</pre>
 +
 +
I like to manually run the "sync" command a couple of times just to make sure the disks are all synced up!  Here's is me doing so:
 +
<pre style="color:blue">
 +
[root@server.dawgland.com:~]# sync
 +
[root@server.dawgland.com:~]# sync
 +
[root@server.dawgland.com:~]# sync
 +
[root@server.dawgland.com:~]#
 +
</pre>
 +
 +
I then use the "fdisk" tool again to view my changes.  As can be seen, although the 4 partitions had vanished, as intended, it still shows the deives contains an 'exfat' signature, and althoug it states it will be removed by a "write" command, doing the "w" command does NOT remove the 'exfat' signature, as seen in this example:
 +
<pre style="color:blue">
 +
[root@server.dawgland.com:~]# fdisk /dev/sdl
 +
 +
Welcome to fdisk (util-linux 2.35.2).
 +
Changes will remain in memory only, until you decide to write them.
 +
Be careful before using the write command.
 +
 +
The device contains 'exfat' signature and it will be removed by a write command. See fdisk(8) man page and --wipe option for more details.
 +
 +
Command (m for help):
 +
</pre>
 +
 +
To resolve this issue, the "wipe" options must be CORRECTLY used, as shown in this example:
 +
<pre style="color:blue">
 +
[root@server.dawgland.com:~]# fdisk -W always /dev/sdl
 +
 +
Welcome to fdisk (util-linux 2.35.2).
 +
Changes will remain in memory only, until you decide to write them.
 +
Be careful before using the write command.
 +
 +
The device contains 'exfat' signature and it will be removed by a write command. See fdisk(8) man page and --wipe option for more details.
 +
 +
Command (m for help): w
 +
 +
The partition table has been altered.
 +
Calling ioctl() to re-read partition table.
 +
Syncing disks.
 +
 +
[root@server.dawgland.com:~]# sync
 +
[root@server.dawgland.com:~]# sync
 +
[root@server.dawgland.com:~]# fdisk /dev/sdl
 +
 +
Welcome to fdisk (util-linux 2.35.2).
 +
Changes will remain in memory only, until you decide to write them.
 +
Be careful before using the write command.
 +
 +
Device does not contain a recognized partition table.
 +
Created a new DOS disklabel with disk identifier 0xe345e7b0.
 +
 +
Command (m for help):q
 +
[root@server.dawgland.com:~]#
 +
</pre>
 +
 +
As you can now see, the 'exfat' signature warning is not gone!  The disk can now be safely and correctly partitioned as normal!
 +
 +
 +
 +
 +
 +
*** '''The "wipe" switch has a caveat which requires the addition of "always" being used after the -W switch, which must be an upper-case W.  Here is an example from a disk that had been partioned and formated using the "ExFAT" partition and filesystem, which held onto the 'exfat' signature and didn't want to clear it by a normal delete partion command and write partition table command.  It still showed as 'exfat', as seen in these examples!
 +
 +
 
*  df - DiskFree - Shows how much space is used by files, and how much space is left on storage devices connected to the system in one way or another, both locally mounted and remotely mounted file systems.
 
*  df - DiskFree - Shows how much space is used by files, and how much space is left on storage devices connected to the system in one way or another, both locally mounted and remotely mounted file systems.
 
*  du - DiskUsage - Shows how much space is used by files.
 
*  du - DiskUsage - Shows how much space is used by files.

Latest revision as of 00:23, 11 August 2024

Guides, Info & Tips on New Modern Linux Server Administration

Modern Server Administration of Critical Systems


This information pertains to very modern recent relases of Redhat based distributions, including the latest releases of CentOS and Fedora, which has had most of these service upgrades and replacements for the last few years now!



Basic Linux System Commands - System Management


TMUX - Terminal Multiplexer

TMUX is what I consider one of the most invaluable tools when it comes to managing and administering Linux servers from the command line. Among it's many features is it's ability to keep your shell connection running in the event of beding disconnected from a remote SSH session. If used properly, it allows you to reconnect to your SSH session you had running, along with whatever applicatoins, scripts, etc, you had running, without losing a beat! It's really handhy to be able to reconnect to a remote session that was inadvertently disconnected! TMUX has saved my butt many times over the years! It also can be used to open multiple shell connections all in the same window, allowing you to split one terminal into two, four, and so on! Plus, you can share the terminal with other remote users, so they can see waht you are typing, and they can also type and you control the same shell! That comes in very handy when you need to show someone how to do something within a shell.

Here is the very simple installation process on a Red Hat based distribution, on Rocky Linux 9.2:


[jamie@rocky9vm32.dawgland.com:~]$ sudo dnf install tmux
Last metadata expiration check: 1:30:38 ago on Thu 05 Oct 2023 12:25:59 AM PDT.
Dependencies resolved.
================================================================================
 Package        Architecture     Version                 Repository        Size
================================================================================
Installing:
 tmux           x86_64           3.2a-4.el9              baseos           474 k

Transaction Summary
================================================================================
Install  1 Package

Total download size: 474 k
Installed size: 1.1 M
Is this ok [y/N]: y
Downloading Packages:
tmux-3.2a-4.el9.x86_64.rpm                      612 kB/s | 474 kB     00:00    
--------------------------------------------------------------------------------
Total                                           270 kB/s | 474 kB     00:01     
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
  Preparing        :                                                        1/1 
  Installing       : tmux-3.2a-4.el9.x86_64                                 1/1 
  Running scriptlet: tmux-3.2a-4.el9.x86_64                                 1/1 
  Verifying        : tmux-3.2a-4.el9.x86_64                                 1/1 

Installed:
  tmux-3.2a-4.el9.x86_64                                                        

Complete!
[jamie@rocky9vm32.dawgland.com:~]$



Using TMUX

Using TMUX is as simple as just typing it's name. It will change the color and look of your prompt to indicate it's running.


System Power Off & Reboot

The "shutdown" command has a number of arguments that control how it behaves, such as shutting completely down, or rebooting, with options to send system-wide broadcast messages to all logged in users, apply a delay before shutting down, and other options.

For a simple quick reboot, the alias "reboot" causes an immediate shutdown and startup, resulting in a reboot, hence the name of the command!

As with most all system control commands, you must have eleveated privilges to be the root user, or a memeber of the correct group to allow for usage of sudo to run commands as the root, aka, superuser/administrator. So, as the root user, just typing "reboot" from the command line causes in immediate system reboot without warning or options! If you are not logged in as the root user, then using sudo, assuming you are in the corect sudoers group, to allow you to run the command as if you were logged in as the root user. The command "sudo reboot" then causes an immediate reboot without warning.

The real command to shutdown and reboot the system is the "shutdown" command, with appropriate switches and/or arguments. For instance, to reboot the system now, just as before, but using the shutdown command, the full command to reboot using the shutdown command is as follows: 

[jamie@rocky9vm35.dawgland2.com:~]$ sudo shutdown -r now
[jamie@rocky9vm35.dawgland2.com:~]$ Connection to rocky9vm35 closed by remote host.
Connection to rocky9vm35 closed.



To shut down a system completely, without starting it back up, instead of using the "-r" switch without the quotes, as in the previous example, you use the "-h" switch, without the quotes, as in this example: 

[jamie@rocky9vm35.dawgland2.com:~]$ sudo shutdown -h now
[jamie@rocky9vm35.dawgland2.com:~]$ Connection to rocky9vm35 closed by remote host.
Connection to rocky9vm35 closed.



To add a time deley to the shutdown command, so as to allow logged in userrs to have time to log out cleanly, modify the command as follows to include a 30 second time delay before actually shutting down, as show here: 

[jamie@rocky9vm35.dawgland2.com:~]$ sudo shutdown -h -t 30
Shutdown scheduled for Mon 2023-09-11 19:15:53 PDT, use 'shutdown -c' to cancel.
[jamie@rocky9vm35.dawgland2.com:~]$ Connection to rocky9vm35 closed by remote host.
Connection to rocky9vm35 closed.



Users logged into the same machine will see messages similiar to this when a time delay is given to the shutdown command: 

[jamie@rocky9vm35.dawgland2.com:~]$ 
Broadcast message from root@rocky9vm35.dawgland2.com on pts/0 (Mon 2023-09-11 19:14:53 PDT):

The system will power off at Mon 2023-09-11 19:15:53 PDT!


Broadcast message from root@rocky9vm35.dawgland2.com on pts/0 (Mon 2023-09-11 19:15:53 PDT):

The system will power off now!

Connection to rocky9vm35 closed by remote host.
Connection to rocky9vm35 closed.



And last, but certently not lease, here is an example to reboot a system in ONE minute, while broadcasting a custom message to all logged on users: 

[jamie@rocky9vm35.dawgland2.com:~]$ sudo shutdown -r +1 "This Server, Rocky9VM35, will be going down in ONE MINUTE for a quick reboot. Please finish up your work and log off immediatelly!"



This produces these messages in the terminal that called the command: 

Reboot scheduled for Mon 2023-09-11 19:33:46 PDT, use 'shutdown -c' to cancel.
[jamie@rocky9vm35.dawgland2.com:~]$ Connection to rocky9vm35 closed by remote host.
Connection to rocky9vm35 closed.



Other users logged into the same system will receive messages similar to these: 

[jamie@rocky9vm35.dawgland2.com:~]$ 
Broadcast message from root@rocky9vm35.dawgland2.com on pts/0 (Mon 2023-09-11 19:32:46 PDT):

This Server, Rocky9VM35, will be going down in ONE MINUTE for a quick reboot. Please finish up your work and log off immediatelly!
The system will reboot at Mon 2023-09-11 19:33:46 PDT!


Broadcast message from root@rocky9vm35.dawgland2.com on pts/0 (Mon 2023-09-11 19:33:46 PDT):

This Server, Rocky9VM35, will be going down in ONE MINUTE for a quick reboot. Please finish up your work and log off immediatelly!
The system will reboot now!

Connection to rocky9vm35 closed by remote host.
Connection to rocky9vm35 closed.



systemctl

init.d Retired!

The first such service upgrade actually replaced most, if not all of the service init.d startup & shutdown scripts with a very different way of managing the startup, status and shutdown of services, such as the Apache webserver, the CUPS print server, the secure shell, aka the SSH server, and all of the other services that used to be controlled by shell scripts located in the /etc/init.d/ directory. This directory still exists so that in the event that an old legacy service needs to still be managed by the init.d shell scripts, due to the service not yet having the required setup to be managed by the replacement of all of those scripts:



Query Service Status

For instance, here is an example of systemctl being used to query the Secure Shell Server(SSH):

[root@fc24 ~]# systemctl status sshd.service
● sshd.service - OpenSSH server daemon
   Loaded: loaded (/usr/lib/systemd/system/sshd.service; enabled; vendor pres
   Active: active (running) since Sun 2016-09-11 01:12:21 PDT; 1h 20min ago
     Docs: man:sshd(8)
           man:sshd_config(5)
  Process: 791 ExecStart=/usr/sbin/sshd $OPTIONS (code=exited, status=0/SUCCE
 Main PID: 810 (sshd)
    Tasks: 1 (limit: 512)
   CGroup: /system.slice/sshd.service
           └─810 /usr/sbin/sshd

Sep 11 01:12:20 fc24.dawgland.com systemd[1]: Starting OpenSSH server daemon.
Sep 11 01:12:21 fc24.dawgland.com systemd[1]: sshd.service: PID file /var/run
Sep 11 01:12:21 fc24.dawgland.com sshd[810]: Server listening on 0.0.0.0 port
Sep 11 01:12:21 fc24.dawgland.com systemd[1]: Started OpenSSH server daemon.
lines 1-15/15 (END)



Stopping a Service

This is what is looks like after stopping the SSH server:

[root@fc24 ~]# systemctl stop sshd.service
[root@fc24 ~]# systemctl status sshd.service
● sshd.service - OpenSSH server daemon
   Loaded: loaded (/usr/lib/systemd/system/sshd.service; enabled; vendor pres
   Active: inactive (dead) since Sun 2016-09-11 02:38:55 PDT; 10s ago
     Docs: man:sshd(8)
           man:sshd_config(5)
  Process: 791 ExecStart=/usr/sbin/sshd $OPTIONS (code=exited, status=0/SUCCE
 Main PID: 810 (code=exited, status=0/SUCCESS)

Sep 11 01:12:20 fc24.dawgland.com systemd[1]: Starting OpenSSH server daemon.
Sep 11 01:12:21 fc24.dawgland.com systemd[1]: sshd.service: PID file /var/run
Sep 11 01:12:21 fc24.dawgland.com sshd[810]: Server listening on 0.0.0.0 port
Sep 11 01:12:21 fc24.dawgland.com systemd[1]: Started OpenSSH server daemon.
Sep 11 02:38:55 fc24.dawgland.com systemd[1]: Stopping OpenSSH server daemon.
Sep 11 02:38:55 fc24.dawgland.com systemd[1]: Stopped OpenSSH server daemon.
lines 1-14/14 (END)



Starting a Service Back Up

And this is the command to start it back up, and because there is no output after starting it, I've also included the output of the status once again after starting the Secure Shell Server back up:

[root@fc24 ~]# systemctl start sshd.service
[root@fc24 ~]# systemctl status sshd.service
● sshd.service - OpenSSH server daemon
   Loaded: loaded (/usr/lib/systemd/system/sshd.service; enabled; vendor pres
   Active: active (running) since Sun 2016-09-11 02:42:38 PDT; 9s ago
     Docs: man:sshd(8)
           man:sshd_config(5)
  Process: 2801 ExecStart=/usr/sbin/sshd $OPTIONS (code=exited, status=0/SUCC
 Main PID: 2803 (sshd)
    Tasks: 1 (limit: 512)
   CGroup: /system.slice/sshd.service
           └─2803 /usr/sbin/sshd

Sep 11 02:42:38 fc24.dawgland.com systemd[1]: Starting OpenSSH server daemon.
Sep 11 02:42:38 fc24.dawgland.com systemd[1]: sshd.service: PID file /var/run
Sep 11 02:42:38 fc24.dawgland.com sshd[2803]: Server listening on 0.0.0.0 por
Sep 11 02:42:38 fc24.dawgland.com systemd[1]: Started OpenSSH server daemon.
lines 1-15/15 (END)



Disabling a Service


To Disable a service, usually replacing status, start, or stop with "disable" works to disable most services, but sometimes, it doesn't always work, and you also need to "mask" the service as well.

Using Mask to Forcefully Disable a Service

This proved to be the case with the RPCBIND.service. After stopping and disabling the service, a reboot caused the service to be re-enabled and started back up. To have the service disabled and that state saved after a reboot, the "mask" argument is given to the systemctl command. For instance, in the case of RPCBIND.service, this is how to disable it:
(In the below example, ONLY the 3 commands starting with systemctl are typed by the root superuser) 

[root@vm1 ~]# systemctl stop rpcbind.service
Warning: Stopping rpcbind.service, but it can still be activated by:
  rpcbind.socket
[root@vm1 ~]# systemctl disable rpcbind.service
[root@vm1 ~]# systemctl mask rpcbind.service
ln -s '/dev/null' '/etc/systemd/system/rpcbind.service



Changing the Default Run Level the Systemd Way


To change the default run-level from booting up into the Graphical User Interface(GUI) into straight text multi-user, which is preferable on a server, the old method involved editing the /etc/inittab file changing the default runlevel from 5 to 3, as shown here: 

id:3:initdefault:



On modern RPM based systems, this has been replaced by using the systemctl command to create/change the symlink /etc/systemd/system/default.target to point to /lib/systemd/multi-user.target, and visa-versa to switch back to the GUI bootup mode. This can be done manually using the shell "ln -sf" symlink creation command, or more easily, and more importantly, more standardized with the systemctl command, as shown here. The following 3 commands show how to first check the default runlevel target, then change it from graphical to text-based multi-user, and then the 3rd command show's confirmation the command was successful. 

[root@fc21 ~]# systemctl get-default
graphical.target
[root@fc21 ~]# systemctl set-default multi-user.target
Removed symlink /etc/systemd/system/default.target.
Created symlink from /etc/systemd/system/default.target to /usr/lib/systemd/system/multi-user.target.
[root@fc21 ~]# systemctl get-default
multi-user.target

dnf


Another BIG change to a "more modern" way of managing all of the software packages on your Linux machine, is the dnf command that is a direct drop-in replacement for yum, the old, tried and true RPM package manager that for going on 20 years has been the main interface to manage Linux software installations, taking into account all of the required dependencies, as well as uninstalling, more commonly referred to "removing" software packages.

Here is an example of how to use dnf to first search for, and then install over the internet, Blender, a very powerful tool to create your own custom animation, simulations and movies: 

[root@fc24 ~]# dnf search blender
Last metadata expiration check: 2:29:11 ago on Sun Sep 11 00:31:02 2016.
=========================== N/S Matched: blender ============================
blender.x86_64 : 3D modeling, animation, rendering and post-production



After searching for and finding the package I want to install, I then use dnf, NOT YUM!, to perform the dependency checking, downloading of the package along with the required dependencies, install all of the packages, and then perform what is called the "Cleanup" portion of the process.

This is how to use dnf to download, install, and then clean up any left over junk: 

[root@fc24 ~]# dnf install blender
Last metadata expiration check: 2:30:45 ago on Sun Sep 11 00:31:02 2016.
Dependencies resolved.
=============================================================================
 Package                      Arch      Version             Repository  Size
=============================================================================
Installing:
 Field3D                      x86_64    1.7.2-1.fc24        updates    519 k
 OpenColorIO                  x86_64    1.0.9-11.fc24       fedora     439 k
 OpenImageIO                  x86_64    1.6.16-1.fc24       updates    1.7 M
 blender                      x86_64    1:2.77a-1.fc24      updates     29 M
 boost-locale                 x86_64    1.60.0-7.fc24       updates    279 k
 boost-program-options        x86_64    1.60.0-7.fc24       updates    166 k
 boost-regex                  x86_64    1.60.0-7.fc24       updates    300 k
 fftw-libs-double             x86_64    3.3.4-7.fc24        fedora     805 k
 fonts-blender                noarch    1:2.77a-1.fc24      updates    4.7 M
 google-droid-sans-fonts      noarch    20120715-10.fc24    fedora     2.5 M
 hdf5                         x86_64    1.8.16-3.fc24       fedora     1.7 M
 jack-audio-connection-kit    x86_64    1.9.10-5.fc24       fedora     555 k
 jemalloc                     x86_64    4.2.1-1.fc24        updates    182 k
 libffado                     x86_64    2.2.1-8.fc24        fedora     690 k
 libspnav                     x86_64    0.2.3-3.fc24        fedora      17 k
 libxml++                     x86_64    2.40.1-2.fc24       fedora      89 k
 pugixml                      x86_64    1.7-2.fc24          fedora      92 k
 python3-numpy                x86_64    1:1.11.0-4.fc24     fedora     3.0 M
 tinyxml                      x86_64    2.6.2-11.fc24       fedora      54 k
 yaml-cpp03                   x86_64    0.3.0-9.fc24        fedora     151 k

Transaction Summary
=============================================================================
Install  20 Packages

Total download size: 47 M
Installed size: 178 M
Is this ok [y/N]: y



Red Hat Enterprise Linux 5,6 & 7 - Common Administrative Command Cheat Sheets

Here are some very nice printable cheat sheets of the most common Red Hat Enterprise Linux administrative commands:
RedHatEnterpriseLinux_5_6_7_Cheatsheets.pdf

File System Tools & Utilities

There are hundreds if not thousands of file system tools, utilities and apps, so here I will try to go over the main, best, and most useful file system tools in my opinion. This section will have to be a "work in progress", and I will add to this section as time permites, as I find myself needing to use these applilcations.

ALL of these tools and utilities must be ran as either the root superuser, or using the "sudo" prefix!

FDISK

fdisk, the disk partitionling command-line tool, as are all Linux command line commands, Case Sensitive, and therefore always lower case! fdisk doesn't always need switches, but ALWAYS MUST have arguments! In the case of fdisk, the most common switch is the "l" switch, a lower-case L. It's used to only LIST, and NOT change/modify any disk partitions. The "l" switch spits out the current partition pointed to with the argument, which is always a Linux "device" file, such as "/dev/sda", case sensitive, without the quotes. /dev/sda is the first hard drive, with the "s" part referring to the old SCSI protocol. Therefore, /dev/sda referres to SCSI device A, the first drive in a Linux system. The next drive would be /dev/sdb, the third drive would be /dev/sdc, and so on.

On more modern systems, that don't use old-school hard drives, the newest technology drives used for storage, especially on laptops, are M.1 drives, which are solid-state drives which usually use the NVMe standard, making the device files for those drives something like /dev/nvme01p0, or similar. CD & DVD writers(also referred to "burners"), often use "/dev/sr0" as the first CD/DVD burner on a system, which stand for "SCSI Recorder Number 0", since numbering usually starts with 0 on computer systems.

Regardless of the device files being used, the "fdisk" commands are all basically the same, other than the actual device you are partitionling, which is CRITICAl, as there is NO going back once you have partitioned and written that partion table to the drive!!! Therefore, you MUST ALWAYS be 100% CERTAIN you are using the correct hard of solid-state drive file!!!

One more BIG concern to take into account is if the disk already has an existing partion table created, from being previously used, you MUST be sure to use the CORRECT disk partitioning tools, as newer, larger and more modern computers use the new disk partitioning tool called GDISK, instead of FDISK! Both are used with all Lower Case letters(fdis & gdisk), but if there is already a "gdisk" partioned disk, known as a "GPT" partition table, you MUST use the "gdisk" tool to make any changes/modification to the disk's partition table, and visa versa in the case of a disk with an existing "fdisk" partion table, known as the "DOS" partition table type. It usually shows as all lower-case, such as "dos".

Usesage of both partitioning tools are almost identicle, with the only real differences being the partition type hex-codes used to define the partition types at creation time.

The first step is the unmount the USB flash drive, before using any partitioning tools, as it can otherwise corrupt the drive. Because I am using an existing 256GB USB 3.0 flash drive, I prefer to use the udiskctl utility to both unmount and power-off USB flash drives. Here is the command I use to "unmount" the drive, before making any changes to it's partition table: 

[root@server.dawgland.com:~]# udisksctl unmount -b /dev/sdl
Unmounted /dev/sdl.
[root@server.dawgland.com:~]#

Next, I need to use the fdisk tool to delete the existing partitions on the USB flash drive: 

[root@server.dawgland.com:~]# fdisk /dev/sdl

Welcome to fdisk (util-linux 2.35.2).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

The device contains 'exfat' signature and it will be removed by a write command. See fdisk(8) man page and --wipe option for more details.

Command (m for help): p

Disk /dev/sdl: 234.38 GiB, 251658240000 bytes, 491520000 sectors
Disk model: ProductCode     
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x00000000

Device     Boot      Start        End    Sectors  Size Id Type
/dev/sdl1       4294967295 8589934589 4294967295    2T ff BBT
/dev/sdl2       4294967295 8589934589 4294967295    2T ff BBT
/dev/sdl3       4294967295 8589934589 4294967295    2T ff BBT
/dev/sdl4       4294967295 5035196669  740229375  353G ff BBT

Command (m for help): d
Partition number (1-4, default 4): 

Partition 4 has been deleted.

Command (m for help): d
Partition number (1-3, default 3): 

Partition 3 has been deleted.

Command (m for help): d
Partition number (1,2, default 2): 

Partition 2 has been deleted.

Command (m for help): d
Selected partition 1
Partition 1 has been deleted.

Command (m for help): p
Disk /dev/sdl: 234.38 GiB, 251658240000 bytes, 491520000 sectors
Disk model: ProductCode     
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x00000000

Command (m for help): w
The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

[root@server.dawgland.com:~]#

I like to manually run the "sync" command a couple of times just to make sure the disks are all synced up! Here's is me doing so: 

[root@server.dawgland.com:~]# sync
[root@server.dawgland.com:~]# sync
[root@server.dawgland.com:~]# sync
[root@server.dawgland.com:~]#

I then use the "fdisk" tool again to view my changes. As can be seen, although the 4 partitions had vanished, as intended, it still shows the deives contains an 'exfat' signature, and althoug it states it will be removed by a "write" command, doing the "w" command does NOT remove the 'exfat' signature, as seen in this example: 

[root@server.dawgland.com:~]# fdisk /dev/sdl

Welcome to fdisk (util-linux 2.35.2).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

The device contains 'exfat' signature and it will be removed by a write command. See fdisk(8) man page and --wipe option for more details.

Command (m for help):

To resolve this issue, the "wipe" options must be CORRECTLY used, as shown in this example: 

[root@server.dawgland.com:~]# fdisk -W always /dev/sdl

Welcome to fdisk (util-linux 2.35.2).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

The device contains 'exfat' signature and it will be removed by a write command. See fdisk(8) man page and --wipe option for more details.

Command (m for help): w

The partition table has been altered.
Calling ioctl() to re-read partition table.
Syncing disks.

[root@server.dawgland.com:~]# sync
[root@server.dawgland.com:~]# sync
[root@server.dawgland.com:~]# fdisk /dev/sdl

Welcome to fdisk (util-linux 2.35.2).
Changes will remain in memory only, until you decide to write them.
Be careful before using the write command.

Device does not contain a recognized partition table.
Created a new DOS disklabel with disk identifier 0xe345e7b0.

Command (m for help):q
[root@server.dawgland.com:~]#

As you can now see, the 'exfat' signature warning is not gone! The disk can now be safely and correctly partitioned as normal!



      • The "wipe" switch has a caveat which requires the addition of "always" being used after the -W switch, which must be an upper-case W. Here is an example from a disk that had been partioned and formated using the "ExFAT" partition and filesystem, which held onto the 'exfat' signature and didn't want to clear it by a normal delete partion command and write partition table command. It still showed as 'exfat', as seen in these examples!


  • df - DiskFree - Shows how much space is used by files, and how much space is left on storage devices connected to the system in one way or another, both locally mounted and remotely mounted file systems.
  • du - DiskUsage - Shows how much space is used by files.
  • ls - List - List files with a multitude of options and switches. I use ls -l, of which there usually exists an alias using "ll" as a shortcut to the "ls -l" command. The -l switch shows a Long listing, which means it shows not only file names, but file sizes and file attrubutes, ownerships, etc. I often add the "-a" switch to the "ls" command as well, meaning show "ALL" files, including "hidden" files, which start with a dot to hide them from a normal directory listing. So, I usually always use "ls -al" to list the contents of a directory, such as here:


[jamie@rocky9vm32.dawgland.com:~]$ ls -al
total 20
drwx------. 7 jamie jamie  170 Oct  5 02:01 .
drwxr-xr-x. 3 root  root    19 Jan 26  2023 ..
drwx------. 3 jamie jamie   17 Oct  4 23:04 .ansible
-rw-------. 1 jamie jamie 2875 Oct  5 02:10 .bash_history
-rw-r--r--. 1 jamie jamie   18 Nov  1  2022 .bash_logout
-rw-r--r--. 1 jamie jamie  141 Nov  1  2022 .bash_profile
-rw-r--r--. 1 jamie jamie  660 Jan 27  2023 .bashrc
drwx------. 3 jamie jamie   24 Jul 25 21:40 .cache
drwx------. 3 jamie jamie   17 Jul 25 21:38 .config
-rw-------. 1 jamie jamie   20 Oct  5 02:01 .lesshst
drwx------. 3 jamie jamie   19 Jul 25 21:38 .local
drwx------. 2 jamie jamie   61 Jan 27  2023 .ssh
[jamie@rocky9vm32.dawgland.com:~]$



MariaDB - The "Free" MySQL Alternative


MySQL, the long time "free" SQL server and client that used to be included in all standard Linux server installations server, has been acquired by Oracle, and they've "commercialized" it, so that it is no longer "officially" free for any commercial or business usage, and only "free" for personal not-for-profit use. This caused a bunch of long time developers to create what has become the "de-facto" MySQL replacement, and uses the exact same MySQL commands and syntax that we have become accustomed to throughout the years.

Installation of MariaDB

This is how I installed MariaDB on my new Fedora Linux 24, the latest and greatest! In one command, I've installed both the server and client, along with all of their dependencies! Here's how I did it: 

[root@fc24 ~]# dnf install mariadb-server mariadb
Last metadata expiration check: 3:08:41 ago on Sun Sep 11 00:31:02 2016.
Dependencies resolved.
=============================================================================
 Package                Arch        Version               Repository    Size
=============================================================================
Installing:
 mariadb                x86_64      3:10.1.16-1.fc24      updates      6.3 M
 mariadb-common         x86_64      3:10.1.16-1.fc24      updates       66 k
 mariadb-config         x86_64      3:10.1.16-1.fc24      updates       29 k
 mariadb-errmsg         x86_64      3:10.1.16-1.fc24      updates      203 k
 mariadb-libs           x86_64      3:10.1.16-1.fc24      updates      654 k
 mariadb-server         x86_64      3:10.1.16-1.fc24      updates       19 M
 perl-DBD-MySQL         x86_64      4.036-1.fc24          updates      146 k
 perl-DBI               x86_64      1.634-3.fc24          fedora       729 k
 perl-Math-BigInt       noarch      1.9997.15-2.fc24      fedora       178 k
 perl-Math-Complex      noarch      1.59-362.fc24         updates       95 k
 perl-Storable          x86_64      1:2.53-348.fc24       updates       84 k

Transaction Summary
=============================================================================
Install  11 Packages

Total download size: 28 M
Installed size: 140 M
Is this ok [y/N]:y



Here is the rest of the output from the "dnf" after hitting the "Y" key to proceed to download the installation RPM packages, install them, and then clean things up to finish the installation: 

Downloading Packages:
(1/11): mariadb-common-10.1.16-1.fc24.x86_64 158 kB/s |  66 kB     00:00    
(2/11): perl-DBI-1.634-3.fc24.x86_64.rpm     1.3 MB/s | 729 kB     00:00    
(3/11): perl-Math-BigInt-1.9997.15-2.fc24.no 1.9 MB/s | 178 kB     00:00    
(4/11): mariadb-errmsg-10.1.16-1.fc24.x86_64 361 kB/s | 203 kB     00:00    
(5/11): mariadb-config-10.1.16-1.fc24.x86_64 295 kB/s |  29 kB     00:00    
(6/11): perl-DBD-MySQL-4.036-1.fc24.x86_64.r 532 kB/s | 146 kB     00:00    
(7/11): mariadb-libs-10.1.16-1.fc24.x86_64.r 930 kB/s | 654 kB     00:00    
(8/11): perl-Math-Complex-1.59-362.fc24.noar 1.0 MB/s |  95 kB     00:00    
(9/11): perl-Storable-2.53-348.fc24.x86_64.r 1.0 MB/s |  84 kB     00:00    
(10/11): mariadb-10.1.16-1.fc24.x86_64.rpm   2.2 MB/s | 6.3 MB     00:02    
(11/11): mariadb-server-10.1.16-1.fc24.x86_6 3.8 MB/s |  19 MB     00:05    
-----------------------------------------------------------------------------
Total                                        4.3 MB/s |  28 MB     00:06     
Running transaction check
Transaction check succeeded.
Running transaction test
Transaction test succeeded.
Running transaction
  Installing  : mariadb-config-3:10.1.16-1.fc24.x86_64                  1/11 
  Installing  : mariadb-common-3:10.1.16-1.fc24.x86_64                  2/11 
  Installing  : mariadb-errmsg-3:10.1.16-1.fc24.x86_64                  3/11 
  Installing  : mariadb-3:10.1.16-1.fc24.x86_64                         4/11 
  Installing  : mariadb-libs-3:10.1.16-1.fc24.x86_64                    5/11 
  Installing  : perl-Storable-1:2.53-348.fc24.x86_64                    6/11 
  Installing  : perl-Math-Complex-1.59-362.fc24.noarch                  7/11 
  Installing  : perl-Math-BigInt-1.9997.15-2.fc24.noarch                8/11 
  Installing  : perl-DBI-1.634-3.fc24.x86_64                            9/11 
  Installing  : perl-DBD-MySQL-4.036-1.fc24.x86_64                     10/11 
  Installing  : mariadb-server-3:10.1.16-1.fc24.x86_64                 11/11 
  Verifying   : mariadb-server-3:10.1.16-1.fc24.x86_64                  1/11 
  Verifying   : perl-DBI-1.634-3.fc24.x86_64                            2/11 
  Verifying   : mariadb-common-3:10.1.16-1.fc24.x86_64                  3/11 
  Verifying   : mariadb-errmsg-3:10.1.16-1.fc24.x86_64                  4/11 
  Verifying   : perl-Math-BigInt-1.9997.15-2.fc24.noarch                5/11 
  Verifying   : mariadb-3:10.1.16-1.fc24.x86_64                         6/11 
  Verifying   : mariadb-config-3:10.1.16-1.fc24.x86_64                  7/11 
  Verifying   : perl-DBD-MySQL-4.036-1.fc24.x86_64                      8/11 
  Verifying   : mariadb-libs-3:10.1.16-1.fc24.x86_64                    9/11 
  Verifying   : perl-Math-Complex-1.59-362.fc24.noarch                 10/11 
  Verifying   : perl-Storable-1:2.53-348.fc24.x86_64                   11/11 

Installed:
  mariadb.x86_64 3:10.1.16-1.fc24                                            
  mariadb-common.x86_64 3:10.1.16-1.fc24                                     
  mariadb-config.x86_64 3:10.1.16-1.fc24                                     
  mariadb-errmsg.x86_64 3:10.1.16-1.fc24                                     
  mariadb-libs.x86_64 3:10.1.16-1.fc24                                       
  mariadb-server.x86_64 3:10.1.16-1.fc24                                     
  perl-DBD-MySQL.x86_64 4.036-1.fc24                                         
  perl-DBI.x86_64 1.634-3.fc24                                               
  perl-Math-BigInt.noarch 1.9997.15-2.fc24                                   
  perl-Math-Complex.noarch 1.59-362.fc24                                     
  perl-Storable.x86_64 1:2.53-348.fc24                                       

Complete!
[root@fc24 ~]#



Secure MariaDB Database Server Before Enabling SQL Server for Production


Before you enable the MariaDB SQL server, you MUST secure the server, either manually or using the included mysql_secure_installation shell script. Personally, I prefer to do it manually so that I can fine tune and tweak my installation. But the ultimate choice is your's.

Samba/CIFS Information --> Sharing Linux & Windows Stuff - A Necessary Evil~!


Excellent information on Samba 4 and using it to replace Windows AD, can be found here:
Setting up Samba 4 as Windows Active Directory Domain Controller

Password Info & Creation


Usually, passwords are created from the command line using the "passwd" command.
When creating a new user account, by default no password is set, so it must be done so manually!

If you need to create a pasword hash that can be copy and pasted into some other file manually,
there are a number of ways to do it, however I personally prefer a tool that is included with most
Linux distributions, aka "Distros". This tool is part of the Apache web server, so most systems already have it installed.
The htpasswd command is very versatile. This is an example of how to create a password hash manually: 

[root@server ~]# htpasswd -c /tmp/tmppass tim
New password: 
Re-type new password: 
Adding password for user tim
[root@server ~]# cat /tmp/tmppass 
tim:$apr1$2/FJ6Trp$YF8RcdKJvkHKsyrZBQn9N0



The hash is after the "tim:" part, and can be copy and pasted into any file you need it for.

7zip Archive Handling With Linux


Depending on your distro, you will want to get either the 7za package for RPM and APT based distros, and the p7zip packages for Slackware, my preferred server distro!

Fedora VNC Information


This is where the symlink for the vncserver@ service resides

[jamie@server system]$ ls -l vncserver@.service 
-rw-r--r--. 1 root root 1734 Jan 21  2014 vncserver@.service
[jamie@server system]$ pwd
/lib/systemd/system



Puppy Linux

Puppy Linux is one of the tiniest Linux distributions, at only 335MB in size for the 32-bit version. The verified ISO for PuppyLinux Bionic32 can be downloaded from here: https://thebestlinux.com/pub/BionicPup32-19.03-231016.iso

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