Skip to content
(ง ˙o˙)ว

Common Commands

this is overview?

Folder permission

Check folder permission

ls -ld /path/to

Check if you have write permission

Terminal window
[ -w /path/to/folder ] && echo "Writable" || echo "Not Writable"

Understand output

drwxr-xr-x. 12 root root 144 Jan 18 16:54 /usr

  • d : it is a directory
  • rwx: The owner can read(r) write(w) execute(x).
  • r-x: The group can read and execute but not write.
  • r--: Others can only read.

Change folder permission

Grant full ownership to yourself

sudo chown your_username /path/to
this is permanent change

Grant group ownership

sudo chown root:group_name /usr

Grant group some permission

sudo chmod 770 /path/to

  • 7 → Owner (root): Read, Write, Execute
  • 7 → Group (your_username or users): Read, Write, Execute
  • 0 → Others: No access

Apply recursively
sudo chmod -R 770 /path/to/folder

Group

Create a new group

sudo groupadd __groupname__

Add a user to the group

sudo usermod -aG _groupname_ _username_

  • -aG: append the user to the specified group

Lists users in a group

getent group _groupname_

Mount

Install

Terminal window
sudo dnf install ntfs-3g

Find the partition

Terminal window
lsblk

for example : /dev/sdb2

Mount it

Terminal window
sudo mount -t ntfs-3g /dev/sdb2 /mnt/D

-t: specify the file system type

Make it always mount after reboot:

Terminal window
sudo nano /etc/fstab

add line at the end:

/dev/sdb2   /mnt/D   ntfs-3g   defaults   0   0

defaults : mount options

  • rw → Read & write access
  • suid → Allow set-user-ID programs
  • dev → Allow device files (e.g., /dev/null)
  • exec → Allow executing binaries
  • auto → Mount automatically at boot
  • nouser → Only root can mount
  • async → Enable asynchronous I/O

0: Dump option, control filesystem backup

0 means do not backup with the dump command

0 : Filesystem check order, controls fsck (filesystem check) at boot

0 means do not check (recommended for NTFS)
Linux-native filesystems (like ext4) usually have 1 or 2 instead.

Then reload:

Terminal window
sudo mount -a

-a: mount all

Finding

already in a folder, and want to find anything name with “aa” (recursively)
find . -name "*aa*"

ls *aa*

Kernel

Show current kernel
uname -r

List all kernels
rpm -q kernel

Remove certain kernel
sudo dnf remove kernel-<version>

check GRUB so the deleted kernel not display on the GRUB boot menu

  1. checkls /boot/vmlinuz-* /boot/initramfs-* then you might see:
[xxx]$ ls /boot/vmlinuz-*
/boot/vmlinuz-0-rescue-5b633ea425544c99914b0944b06a7c25
/boot/vmlinuz-5.14.0-503.23.1.el9_5.x86_64
/boot/vmlinuz-5.14.0-503.23.2.el9_5.x86_64
[xxx]$ ls /boot/initramfs-*
/boot/initramfs-0-rescue-5b633ea425544c99914b0944b06a7c25.img
/boot/initramfs-5.14.0-503.23.1.el9_5.x86_64.img
/boot/initramfs-5.14.0-503.23.1.el9_5.x86_64kdump.img
/boot/initramfs-5.14.0-503.23.2.el9_5.x86_64.img
/boot/initramfs-5.14.0-503.23.2.el9_5.x86_64kdump.img
  1. remove everything about this kernel, full clean it
Terminal window
sudo dnf remove $(rpm -qa | grep 5.14.0-503.35.1.el9_5)

Copy

  • copy from our machine to a remote machine:
    scp myfile.txt ubuntu@192.168.1.30:/home/ubuntu/toRemoteHere.txt

copy from remote machine to our machine
scp ubuntu@192.168.1.30:/home/ubuntu/remoteFile.txt toLocalHere.txt

Serve

Turn your computer into a quick and easy web server

python3 -m http.server
python3 -m http.server 8000

  • -m: tell python to run a module as a script

System

systemd

Linux init system, they start when the system start

systemctl

systemctl is a command allows us to interact with the systemd process / daemon

echo "test 123" & when adding & at the end, it means put echo "test 123" in the background, and return an ID Number

check certain program PID

pgrep sshd

commandDescription
pgrep sshdcheck certain program’s PID
echo $!check latest programs
ps auxcheck current running program

sudo ncdu . check the disk space
nvtop check gpu and other parts live-time status
mc : terminal version browsing the files
watch -n1 nvidia-smi : live-time check nvidia graphic card status