====== Linux ======

  -**[[linux:bash|Bash]]**
  -**[[linux:git|Git basics]]**
  -**[[linux:eGPU|Razer Core eGPU]]**
  -**[[linux:RBS|Razer Blade Stealth in Linux]]**

====== System & Diagnostics ======

===== Logs =====

Common system logs:

<code>
/var/log/syslog
</code>

View recent entries:

<code bash>
tail -f /var/log/syslog
</code>

List recently modified log files:

<code bash>
ls -lt /var/log
</code>

<WRAP info>
**Notes:**

  * ''tail -f'' follows logs in real time
  * On systemd systems, ''journalctl'' is often preferred
</WRAP>

===== System information =====

=== General overview: ===

<code bash>
inxi -F
</code>

=== Distribution: ===

<code bash>
lsb_release -d
</code>

=== Kernel: ===

<code bash>
uname -snrm
</code>

Flags:

  *''s'': kernel name
  *''n'': network node hostname
  *''r'': kernel relase number
  *''m'': machine hardware name


=== CPU: ===

<code bash>
lscpu
cat /proc/cpuinfo
</code>

=== Memory: ===

<code bash>
free -h
</code>

=== Mounted filesystems: ===

<code bash>
df -h
</code>

=== Kernel modules: ===

<code bash>
lsmod
</code>

=== Bash history: ===

<code bash>
history
</code>

----

===== Diagnostics =====

<code bash>
uptime              # load average
dmesg -T | tail     # recent kernel messages
vmstat 1            # system performance
mpstat -P ALL 1     # CPU usage per core
pidstat             # process statistics
free -h             # memory usage
</code>


====== Storage & Filesystems ======

===== Mounting =====

=== List mounts: ===

<code bash>
findmnt
</code>

=== List disks: ===

<code bash>
lsblk
</code>

=== Mount: ===

<code bash>
sudo mkdir -p /media/DRIVE
sudo mount /dev/sdX# /media/DRIVE
</code>

=== Unmount: ===

<code bash>
sudo umount /media/DRIVE
</code>

----

==== Samba ====

Manage service:

<code bash>
sudo systemctl start smbd
sudo systemctl stop smbd
sudo systemctl restart smbd
</code>

----

===== Mount/Repair NTFS =====

If an NTFS volume mounts as read-only, it is usually due to an unclean shutdown or filesystem inconsistency.

Attempt repair:

<code bash>
sudo ntfsfix /dev/sdX#
</code>

Then remount:

<code bash>
sudo mount -t ntfs3 /dev/sdX# /mnt/ntfs
</code>

Create mount point if needed:

<code bash>
sudo mkdir -p /mnt/ntfs
</code>

<WRAP info>
**Notes:**

  * ''ntfsfix'' performs basic repairs and clears the "dirty" flag
  * Full repair should be done from Windows using ''chkdsk''
  * If the issue persists, ensure Windows Fast Startup is disabled
</WRAP>

===== Repair FAT32 filesystem errors =====

If a FAT32 filesystem mounts as read-only, it is often due to detected corruption.

Check kernel logs:

<code bash>
dmesg
</code>

Typical errors:

<code bash>
FAT-fs (sdb1): error, corrupted directory (invalid entries)
FAT-fs (sdb1): Filesystem has been set read-only
FAT-fs (sdb1): error, invalid access to FAT
</code>

Repair the filesystem:

<code bash>
sudo umount /dev/sdX#
sudo fsck.vfat -a -w /dev/sdX#
</code>

  * ''-a'' automatically repair filesystem
  * ''-w'' write changes to disk

Note: Ensure the correct device is targeted before running ''fsck''.


====== File & Data Operations ======

===== Shell toolbox =====

==== File operations ====

=== Mass renaming ===

Uppercase .JPG to lowercase .jpg

<code bash>
for i in *.JPG; do mv "$i" "${i/.JPG/.jpg}"; done
</code>

Alternative (rename tool):

<code bash>
rename 's/\.JPG$/.jpg/' *.JPG
</code>

----

=== Empty a file ===

<code bash>
: > /path/to/file
</code>

----

==== Text processing ====

=== cut ===

Extract part of a string:

<code bash>
date | cut -c17-24
</code>

----

==== Archives ====

=== tar ===

<code bash>
# Extract
tar -xvf file.tar
tar -xvzf file.tar.gz

# Create
tar -cvf file.tar /path/folder
tar -cvzf file.tar.gz /path/folder
</code>

Flags:

  * ''c'' create archive
  * ''x'' extract archive
  * ''v'' verbose (list files processed)
  * ''f'' specify archive file
  * ''z'' gzip compression

----

====== User Environment ======

===== PATH =====
<WRAP round info>
PATH is the //environment variable// containing a list of directories searched for executables.
</WRAP>

<code bash>
# Print PATH
printenv PATH
echo "$PATH"

# Example resolution
ping 127.0.0.1

PATH=/bin:/sbin:/usr/bin:/usr/sbin
       │     │
       │     └── /sbin/ping ? found
       └── /bin/ping ? not found

# Add a folder to PATH (current session only)
PATH=$PATH:/path/to/app/folder
</code>

==== Local installs of binaries and PATH ====

=== Install locations ===

Common locations for manually installed binaries:

<code>
/opt/                 # bundled applications
/usr/local/bin/      # system-wide manual installs
~/.local/bin/        # user-only installs (recommended)
/home/USER/opt/      # alternative user-only location
</code>

[[http://refspecs.linuxfoundation.org/fhs.shtml|FHS Reference]]

=== Add to PATH ===

Add to ''~/.profile'' or ''~/.bashrc'':

<code bash>
export PATH="/path/to/bin:$PATH"
</code>

Apply without logout:

<code bash>
source ~/.profile
</code>

Note: PATH must point to the **directory**, not the binary itself.

=== Locate a binary ===

<code bash>
type man
# man is /usr/bin/man
</code>

----

===== AppImages =====

Run an AppImage:

<code bash>
chmod +x example.AppImage
./example.AppImage
</code>

Some support automatic install:

<code bash>
./example.AppImage --install
</code>

Manual extraction:

<code bash>
./your.AppImage --appimage-extract
</code>

=== Tools ===

  * AppImageLauncher → integrates AppImages into the system (recommended)
  * AppImage Daemon → older alternative

==== Add application to Cinnamon menu ====

Launch menu editor:

<code bash>
cinnamon-menu-editor
</code>

=== Manual method ===

User-level entries:

<code>
~/.local/share/applications/
</code>

Place or create a ''.desktop'' file in this directory.

Example minimal file:

<code>
[Desktop Entry]
Name=My App
Exec=/path/to/executable
Type=Application
Terminal=false
</code>

The entry should appear automatically in the menu.

<WRAP info>
**Note:** Avoid using ''/usr/share/applications/'' unless a system-wide install is required.
</WRAP>


----

===== GRUB =====

Config file:

<code>
/etc/default/grub
</code>

Line for background image:

<code>
GRUB_BACKGROUND=/path/to/image.jpg
</code>

----

===== Limit CPU usage =====

Using ''cpulimit'':

<code bash>
cpulimit -P /path/to/executable -l 40 -b
</code>

----

===== Fonts install =====

System-wide:

<code bash>
sudo cp -r /path/to/fonts /usr/share/fonts/
sudo fc-cache -f -v
</code>

User-only:

<code>
~/.local/share/fonts/
</code>

Then refresh cache:

<code bash>
$ sudo fc-cache -f -v
</code>

----

===== PDF manipulation =====

==== Reorder / split / merge ====

CLI:

<code bash>
pdf-stapler cat in.pdf 2-3 out.pdf
</code>

GUI (recommended):

  * pdfarranger → lightweight, modern, actively maintained

==== Reducing PDF size ====

<code bash>
gs -sDEVICE=pdfwrite -dCompatibilityLevel=1.4 -dPDFSETTINGS=/ebook -dNOPAUSE -dQUIET -dBATCH -sOutputFile=output.pdf input.pdf
</code>

''-dPDFSETTINGS'' presets:

  * ''/screen'' low-resolution output, smallest file, lowest quality
  * ''/ebook'' medium-resolution output, good size/quality compromise
  * ''/printer'' print-oriented output, larger file, higher quality
  * ''/prepress'' prepress-oriented output, larger file, higher quality
  * ''/default'' general-purpose output, can produce larger files

<WRAP info>
**Note:** Ghostscript rewrites the PDF.

It often reduces file size, especially with image-heavy PDFs, but this is not guaranteed.
</WRAP>

===== Video playback (minimal UI) =====

==== mpv (recommended) ====

Lightweight video player with minimal UI, suitable for clean output on external displays.

Example:

<code bash>
mpv --fs --no-border --ontop --geometry=+3200 --osd-level=0 video.mp4
</code>

Common options:

<code>
--fs            # fullscreen
--no-border     # remove window decorations
--ontop         # keep window above others
--geometry=+X+Y # window position (multi-display setups)
--osd-level=0   # disable on-screen display
</code>

Configuration file:

<code>
~/.config/mpv/mpv.conf
</code>

----

==== mplayer (legacy) ====

Legacy setup kept for reference.

Configuration files:

  */etc/mplayer/mplayer.conf
  *~/.mplayer/config
  *~/.mplayer/input.conf
  *~/.mplayer/menu.conf

Example options:

<code>
fs=yes
noborder=yes
ontop=yes
geometry=+3200
osdlevel=0
</code>



====== Specialized & Recovery ======

===== Data recovery =====

Use **TestDisk** / **PhotoRec** as a first recovery tool.

  * **TestDisk** attempts partition repair and file undelete when filesystem metadata is still usable.
  * **PhotoRec** performs file carving by signature. It can recover files from damaged filesystems, but filenames and folder structure are usually lost.

Do not write recovered files to the source disk.

==== PhotoRec: recovered MOV files ====

For some recovered ''.mov'' files, PhotoRec may split the video into separate ''ftyp'' and ''mdat'' parts.

In PhotoRec ''FileOpts'', enable:

<code>
[X] mov/mdat Recover mdat atom as a separate file
</code>

Sort recovered files by name, then try concatenating matching parts:

<code bash>
cat f123_ftyp.mov f456_mdat.mov > recovered_1.mov
cat f456_mdat.mov f123_ftyp.mov > recovered_2.mov
</code>

One order may produce a usable file.

Sometimes the header/container part may be ''.mp4'' while the media data part is ''.mov'':

<code bash>
cat f54114560.mp4 f51781632_mdat.mov > recovered.mov
</code>

Note: This is a recovery attempt, not a guaranteed repair method. For valuable data, stop using the disk immediately and clone/image it before experimenting.



===== Using Apple USB SuperDrive =====

The Apple USB SuperDrive requires a vendor-specific command to activate on non-Apple systems.

=== Required package ===

<code bash>
sudo apt install sg3-utils
</code>

=== Identify device ===

Usually appears as ''/dev/sr0'':

<code bash>
lsblk
</code>

=== Send activation command ===

<code bash>
sudo sg_raw /dev/sr0 EA 00 00 00 00 00 01
</code>

The drive should become usable immediately after.

<WRAP info>
**Note:** This command must be reissued after reconnecting the drive.
</WRAP>

===== QCAD (plugin location) =====

<WRAP center round alert 60%>
NOTE : MOVE TO BOTTOM 'MISC' SECTION AFTER REWRITE
</WRAP>


To locate the QCAD plugin directory:

Go to:
  * Help > About > Plugins (Linux / Windows)
  * QCAD > About > Plugins (macOS)

Click on any plugin name to reveal its file location.

<WRAP info>
**Note:** Useful for locating and removing plugins related to trial limitations.
</WRAP>

===== Screen recording =====

==== Recommended ====

  * **OBS Studio** → full-featured, actively maintained, works for both simple and advanced recording

==== Lightweight alternatives ====

  * simplescreenrecorder → lightweight, reliable on X11
  * vokoscreenNG → simple GUI, good for quick recordings

==== Notes ====

  * Older tools such as Kazam or gtk-recordmydesktop are largely unmaintained and may not work reliably on modern systems
  * Wayland sessions may require OBS or desktop-native recording tools

===== Samba =====

==== List available shares ====

<code bash>
smbclient -L //host -U username
</code>

  * ''host'' → hostname or IP of the server
  * prompts for password

----

==== Access a share (temporary mount) ====

<code bash>
sudo mount -t cifs //host/share /mnt/share -o username=user
</code>

Create mount point if needed:

<code bash>
sudo mkdir -p /mnt/share
</code>

----

==== GUI mounts (file manager) ====

When mounting via a file manager (Nautilus, Nemo, etc.), shares are typically mounted under:

<code>
/run/user/UID/gvfs/
</code>

----

==== Notes ====

<WRAP info>
**Notes:**

  * ''smbclient -L'' is useful for discovery and debugging access issues
  * ''mount -t cifs'' provides a standard way to mount shares in scripts or system configs
  * SMB1 is deprecated and may be disabled on modern systems
</WRAP>

===== Alias =====

Create an alias:

<code bash>
alias name='command'
</code>

Example:

<code bash>
alias ll='ls -lah'
</code>

Aliases are active for the current session only.

To make them persistent, add them to:

<code>
~/.bashrc
</code>

Reload configuration:

<code bash>
source ~/.bashrc
# or
. ~/.bashrc
</code>

----

==== Manage aliases ====

List aliases:

<code bash>
alias
</code>

Remove an alias:

<code bash>
unalias name
</code>

===== Mouse button mapping =====

==== X11 method (xbindkeys) ====

Install tools:

<code bash>
sudo apt install xbindkeys xvkbd
</code>

Identify button codes:

<code bash>
xev | grep button
</code>

Create configuration:

<code bash>
touch ~/.xbindkeysrc
</code>

Example:

<code>
# Send Enter on mouse button 8
"xvkbd -text '\r'"
b:8
</code>

Start xbindkeys:

<code bash>
xbindkeys
</code>

----

<WRAP info>
**Notes:**

  * Works on X11 sessions only
  * Wayland sessions generally do not support this method
  * ''xvkbd'' simulates keypresses; alternative tools may be preferred depending on use case
</WRAP>





==== Package management ====

=== Fix broken packages ===

<code bash>
sudo dpkg --configure -a
sudo apt --fix-broken install
</code>

----



===== Additional Ressources =====

  ***[[https://en.wikipedia.org/wiki/Magic_SysRq_key#Configuration|SysRq Keys]]** -- Best combo is ''Alt + SysRq + R E I S U B''

  ***[[https://www.guruadvisor.net/en/software-saas/465-advanced-linux-troubleshooting-methods-and-tools-for-diagnostics-and-problem-identification|Advanced Linux Troubleshooting]]**

  ***[[https://wiki.networksecuritytoolkit.org/nstwiki/index.php?title=HowTo_Create_A_GPT_Disk_With_EFI_System_And_exFAT_Partitions_Using_Parted|Creating GPT/exFAT partitions using CLI]]**