Debian Reduce System Size

Remove non-critical packages
Replace packages with smaller equivalents
Remove other language man files

Close Gnome Desktop

# stop gnome graphic login program  
systemctl stop gdm

# check gdm status
systemctl status gdm

# get debian system start mode(gui:graphical.target)
systemctl get-default

Network

reset net ip

nmcli networking off
nmcli networking on

check ip

ip a

ftp server setup

# install vsftp
sudo apt install vsftpd

# backup vsftp conf file
sudo /etc/vsftpd.conf /etc/vsftpd.conf.bak

# setup vsftp
sudo vi /etc/vsftpd.conf

# set anonymous_enable
anonymous_enable=YES

# uncomment line
write_enable=YES 

# change default port
# uncomment line below
connect_from_port_20=YES
# add line below
listen_port=21

# uncomment three lines below
chroot_local_user=YES
chroot_list_enable=YES
chroot_list_file=/etc/vsftpd.chroot_list 

# add ftp user, add ftpuser in vsftpd.chroot_list 
sudo vi /etc/vsftpd.chroot_list

# add linux user ftpuser/ftpuserpasswd 
sudo adduser ftpuser 

# check user
more /etc/vsftpd.chroot_list

# check vsftpd conf
sudo cat /etc/vsftpd.conf | grep -v "^#"

# restart VSFTPD service and check the status
sudo systemctl restart vsftpd
sudo systemctl status vsftpd

System

restart, stop, start, check status services

sudo service mysqld restart
sudo service mysqld stop
sudo service mysqld start
sudo service mysqld status

sudo systemctl restart mysqld
sudo systemctl stop mysqld
sudo systemctl start mysqld
sudo systemctl status mysqld

check all exist user

more /etc/passwd
compgen -u
getent passwd

check file size in folder

du -h

find file in system

find /folder/abc/...  -name *abc123*

check disk space

df -TH

check ram usage and clear cache

top
echo 3 | sudo tee /proc/sys/vm/drop_caches

command like ‘ll’ not working

#check .bash_profile and add text below
if [ -f ~/.bashrc ];then
     source .bashrc
fi

check date time

current_day=$(date +"%Y%m%d" 2>&1 | cat)
echo $current_day
current_time=$(date +"%H%M%S" 2>&1 | cat)
echo $current_time

replace text in file

sed -i "s/text1/text2/g" filepath

Reference:

https://wiki.debian.org/ReduceDebian
https://wiki.debian.org/FTP
https://wiki.debian.org/vsftpd