Documentation by Black Sheep Research

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[[useful:contents|Contents Page]]

====== Linux Commands ======

===== Removing comments from config files =====

from 20-lmtp.conf as an example:

     grep '^[[:blank:]]*[^[:blank:]#;]' 20-lmtp.conf

===== Installing a GPG key =====

Example:

     wget -O- https://download.webmin.com/jcameron-key.asc | sudo gpg --dearmor | sudo tee /usr/share/keyrings/jcameron-key.gpg > /dev/null 2>&1 
     
Then need to edit the sources.list file to look something like:

     deb [signed-by=/usr/share/keyrings/jcameron-key.gpg] https://download.webmin.com/download/repository sarge contrib

===== Change permissions for whole directory structure =====

For directories:

    find /desired_location -type d -print0 | xargs -0 chmod 0755
    
For files:

    find /desired_location -type f -print0 | xargs -0 chmod 0644

Adapt as required.

===== Delete all files with given pattern =====

     find . -name '*altauserpoints*' -print0 | xargs -0 -P0 rm
     
Adapt as required.

===== Make a change in every file in a directory  =====

     sed -i 's/foo/bar/g' *
     
To make the change through a whole directory tree:

     find ~/public_html/my_website/pages -type f -exec sed -i 's/2017/2018/g' {} \;
     
===== Search within specific file type =====

     grep -ir removed --include="*.txt" .
     
will search files with extension .txt ignoring case (-i)
     
===== Bluetooth =====

Using this from the command line seems to do more than the GUI:

     bluetoothctl
     
===== Limiting journal log size =====

Edit the file:

     /etc/systemd/journald.conf
     
and set SystemMaxUse, for example

     SystemMaxUse=250M

Then restart journal with:

     systemctl restart systemd-journald