Useful Linux commands

Tags: Linux
Last update: Mar 2018

1. Compare binary files within the console and highlight those areas which differ. Vim and Colordiff have to be installed before.

diff -y <(xxd file.one) <(xxd file.two) | colordiff

2. Using a harddisk device for storing encrypted data:

sudo cryptsetup luksFormat -c aes-xts-plain64 -s 512 -h sha512 -y /dev/sdX
sudo cryptsetup luksOpen /dev/sdX usb-backup
sudo mkfs.btrfs -L backupharddisk /dev/mapper/backup
sudo mount /dev/mapper/backup /usb-backup

3. Mirroring with rsync from /source to /destination. Compression is great when backing up over the Internet.

rsync --compress --compress-level=9 --human-readable -av --progress --delete --log-file=/path/to/log.file /source /destination

4. Wipe a file with zeros:

shred -fvzun 0 file

5. Wipe a directory recursively with zeros:

srm -rvs directory

6. Backup of harddisks into compressed image file. Due to its multithreading capability pigz is much faster than gzip during compression.

sudo dd if=/dev/sdX status=progress bs=1M | pigz > harddisk.img.gz

7. Restore this prior zipped image file and write it directly to disk:

sudo gunzip -c image.gz | sudo dd of=/dev/sdX status=progress bs=1M

8. Recover a Linux Soft-RAID md/5:

sudo mdadm --assemble --scan
sudo cryptsetup luksOpen /dev/md/5 temp
sudo mount /dev/mapper/temp /your_path

9a. Mount a Linux Soft-RAID manually:

sudo mdadm --examine /dev/sdX
sudo mdadm -A -R /dev/md9 /dev/sdX
sudo mount /dev/md9 /openedRaidPartition

9b. And close it again:

sudo umount /openedRaidPartition
sudo mdadm -S /dev/md9

10. List all loadable kernel modules:

find /lib/modules/$(uname -r) -type f -name \*.ko

11. Template for configuring a fresh manjaro xfce installation:

#update system
sudo pacman -Syyu
 
#install zshell
sh -c "$(curl -fsSL https://raw.github.com/robbyrussell/oh-my-zsh/master/tools/install.sh)"
sudo pacman -S powerline-fonts
 
#install virtualbox
sudo pacman -S virtualbox
 
#copy fonts which you need into /usr/share/fonts and run
sudo fc-cache
 
#fixing the Manjaro Linux XFCE text shadow problem on the desktop
xfconf-query -c xfce4-desktop -p /desktop-icons/center-text -n -t bool -s false

12. Nice to have Manjaro packages:

gufw (firewall gui)
chromium (browser)
synapse (launcher)
psensor (temperature)
ether (pendrive tool)
file-roller
p7zip zip unzip unrar
tilda (background terminal)

13. Laravel development quickstart:

git clone project.git
cd project
composer install
composer update
cp .env.example .env
php artisan key:generate
php artisan serve --port=8000

14. Restricting sFTP:

Add to /etc/ssh/sshd_config:

Subsystem sftp internal-sftp
 
  Match Group sftpusers
  ChrootDirectory %h
  ForceCommand internal-sftp
  AllowTcpForwarding no
  X11Forwarding no

Adding user and change configuration:

useradd newuser
usermod -s /bin/false newuser
chown root:root /home/newuser
chmod 755 /home/newuser
mkdir /home/newuser/writablefolder
chown newuser:newuser /home/newuser/writeablefolder
chmod 755 /home/newuser/writeablefolder
 
groupadd sftpusers
usermod -G sftpusers newuser
 
service sshd restart
service vsftpd restart

15. Replacing a broken harddisk (/dev/sda) with two partitions with RAID1 (md0 + md1):

#after having replaced the harddisk; copying MBR partition table
sfdisk -d /dev/sdb | sfdisk /dev/sda
#adding partitions to existing RAID-array md0 and md1:
sudo mdadm /dev/md0 -a /dev/sda1
sudo mdadm /dev/md1 -a /dev/sda2
#reinstalling grub on both disks again, leave options empty, select two disks (/dev/sda + /dev/sdb)
sudo dpkg-reconfigure grub-pc

16. Rsync command which doesn’t copy everything every time while preserving times:

rsync -avP source destination
#a = archive mode
#v = verbose
#P = show progress

17. Bash: interate through alle files within a specific folder and count its files

for i in /folderpath /folderpath ; do 
    echo -n $i": " ; 
    (find "$i" -type f | wc -l) ; 
done