Linux Stuffs

common-uses.md

• Enable sudo and add user to sudoers

  • # apt install sudo
  • # adduser myuser-1 sudo
  • # chmod 0440 /etc/sudoers
  • $ sudo echo "it works"
  • If you have sudo: sudo usermod -aG sudo,group2 myuser-1
  • https://linuxize.com/post/how-to-add-user-to-group-in-linux/

• Installing docker now need a degree: https://docs.docker.com/engine/install/debian/

• less longfile.txt

  Scroll forward: Ctrl-f
  
  Scroll backward: Ctrl-b
  
  End of file: G
  
  Quit less: q

• Get the amount of your physical RAM: grep MemTotal /proc/meminfo

• Kill a process: https://www.cyberciti.biz/faq/how-to-check-running-process-in-linux-using-command-line/

  • find it # ps -aux or # top
  • # kill pid

• https://unix.stackexchange.com/questions/31824/how-do-i-attach-a-terminal-to-a-detached-process

• https://developers.redhat.com/cheat-sheets/linux-commands-cheat-sheet

• https://developers.redhat.com/cheat-sheets/advanced-linux-commands

• check size of folder/ file : https://shapeshed.com/unix-du/

• rsync:

  • https://www.digitalocean.com/community/tutorials/how-to-use-rsync-to-sync-local-and-remote-directories
  • https://linuxize.com/post/how-to-use-rsync-for-local-and-remote-data-transfer-and-synchronization/

ctag_cscope.md

CTAG and CSCOPE

1. First install them sudo apt install ctag cscope

2. For the kernel:

       make defconfig cscope
       ctags R .
   

3. grab this vimrc https://github.com/ddvlad/cfg/blob/master/_vimrc

resources:

• https://linux-kernel-labs.github.io/refs/pull/183/merge/labs/introduction.html
• http://cscope.sourceforge.net/large_projects.html
• https://himadripandya.me/post/185609415870/how-cscope-makes-my-life-easier
• https://www.fsl.cs.sunysb.edu/~rick/cscope.html
• https://www.embeddedarm.com/blog/tag-jumping-in-a-codebase-using-ctags-and-cscope-in-vim/

Disk_Partition.md

• To check if you are usin LVM - Logical Volume Mgmt

  • # apt install lvm2
  • # lvs if nothing is shown then you are not using lvm
  • OR just check: cat /etc/fstab @more - https://askubuntu.com/a/202652/804122

• Ran out of swap ?! How do you extend it

  1. Create or Extend existing partition: https://opensource.com/article/18/9/swap-space-linux-systems https://www.thegeekdiary.com/how-to-extend-an-lvm-swap-partition-in-linux/ https://www.2daygeek.com/add-extend-swap-space-linux/

  2. Create a SWAP file: https://askubuntu.com/questions/178712/how-to-increase-swap-space https://unix.stackexchange.com/questions/297149/how-to-resolve-the-insecure-warning-in-swapon https://linuxize.com/post/create-a-linux-swap-file/ https://linuxhint.com/change_swap_size_ubuntu/

     • make sure the swapfile is owned by root:root
     • make the file permission is 0600
     • why? research and blog

• File Permissions:

  • https://www.namecheap.com/support/knowledgebase/article.aspx/400/205/file-permissions/
  • http://www.filepermissions.com/file-permission/0644
  • http://permissions-calculator.org/decode/0644/
  • MAKE A command line tool with cmd ui

• Free up SWAP: just switch off, wait a bit and switch it back on https://www.redhat.com/sysadmin/clear-swap-linux

• Swapiness Issue"

    60
    saheed@saheed-deb:~$ sudo sysctl vm.swappiness=sudo sysctl vm.swappiness=100
    [sudo] password for saheed: 
    sysctl: setting key "vm.swappiness": Invalid argument
    vm.swappiness = sudo
    sysctl: cannot stat /proc/sys/sysctl: No such file or directory
    vm.swappiness = 100

files_folders_archives.md

1. extract a tar file:

tar -xvf file.tar tar -xzvf file.tar.gz tar -xjvf file.tar.bz2 -x : Extract a tar ball. -v : Verbose output or show progress while extracting files. -f : Specify an archive or a tarball filename. -j : Decompress and extract the contents of the compressed archive created by bzip2 program (tar.bz2 extension). -z : Decompress and extract the contents of the compressed archive created by gzip program (tar.gz extension).

ref: https://www.cyberciti.biz/faq/tar-extract-linux/

networking.md

d

• These tools are all deprecated: ifconfig, ipconfig,, ifup, ifdown, ...

• List interfaces : ip address or ip a; if not found you need to install the driver

• Brint it up: ip link set wlan0 up or down

• I tried to use iw to setup my wifi but it did not work

  • I think this is beacause I have set the wifi interface to allow-hotplug
  • the config setup is done in: /etc/network/interfaces.d
  • It should have looked like: \

        auto eth0
        iface eth0 inet static
                address 192.168.1.10
                netmask 255.255.255.0
                gateway 192.168.1.1
    
        auto wlan0
        iface wlan inet dhcp
                wpa-ssid <my ssid>
                wpa-psk <aes key>
        #        address 192.168.1.11
        #        netmask 255.255.255.0
        #        gateway 192.168.1.1
    

• wpa_supplicant worked instead. Nice setup details is here

  • you will have to setup the config in: /etc/wpa_supplicant/wpa_supplicant.conf

• Very use infor:

  • https://wiki.archlinux.org/index.php/Network_configuration
  • https://wiki.archlinux.org/index.php/Network_configuration/Wireless
  • https://wiki.archlinux.org/index.php/Network_configuration/Ethernet
  • https://www.cyberciti.biz/faq/linux-list-network-cards-command/
  • https://www.linuxbabe.com/command-line/ubuntu-server-16-04-wifi-wpa-supplicant

• Ethernet tool: apt install -y ethtool

  • https://linuxhint.com/ethtool_commands_examples/
  • https://www.thegeekstuff.com/2010/10/ethtool-command/

• GCC and other dev tools: apt install build-essential

• Kernel Headers: apt install linux-headers-$(uname -r)