Basic commands

$ cat /etc/centos-release  # version

$ lspci | grep -i nvidia  # gpu

$ uname -a  # kernel

$ lshw -html > /hardware.html  # print all info

$ lscpu  # cpu info

$ cat /proc/cpuinfo | grep name | cut -f2 -d: | uniq -c  # cpu parameters

$ cat /proc/cpuinfo| grep "physical id"| sort| uniq| wc -l  # physical cpus 

$ cat /proc/cpuinfo| grep "cpu cores"| uniq  # no.cores

$ cat /proc/cpuinfo| grep "processor"| wc -l  # virtual cpus

$ cat /proc/meminfo |grep MemTotal  # memory

$ fdisk -l |grep Disk  # disk info

$ lsscsi  # SSD

$ lsof -i # list the process name and number that has opened the ports

$ netstat -tulnp # see if a program or process is listening on a port, ready to accept a packet

$ systemctl get-default # graphical.target is useless

$ systemctl stop gdm.service

$ systemctl set-default multi-user.target

$ swapoff /dev/dm-1

$ swapon /dev/dm-1

$ swapon -s

$ yumdownloader packagename # off-line install

$ yum --disablerepo='*' install rpm-package

$ chmod -R 700 ./file

$ chown -R user:group ./file

# copy all the files including hidden files

$ cp -a /old/. /folder/

# background, continue, input, output

$ wget -bc -i url.list -o log.txt

# advanced options: -r recursive //-np no-parent //-4 connect only to IPv4 addresses.

# write output to a file named as the remote file

$ curl -O http://file

$ tar -zxvf file -C /dir # -C uncompress to directory //-z for gzip //-j for bzip

$ unzip file -d ./dir # -d uncompress to directory

$ tar -cfz archive.tar.gz file1 file2 file3

$ tar -czPf archive.tar.gz /file_dir -C /outdir  # -P don't strip leading `/'s from file names

$ date -s "2021-11-22 13:15:43"

$ clock -w

$ systemctl restart ntpd.service

$ systemctl stop ntpd.service

$ ntpd -gq

$ systemctl start ntpd.service

username       ALL=(root)      /usr/sbin/*,/sbin/*,/usr/bin/*,!/usr/bin/passwd,!/usr/sbin/visudo,!/usr/sbin/useradd,!/usr/sbin/userdel,!/usr/sbin/reboot,!/usr/sbin/poweroff,!/usr/sbin/shutdown

$ echo 'HISTTIMEFORMAT="%F %T "' >> /etc/profile

$ source /etc/profile

$ rsync -zvh backup.tar /tmp/backups/ # cp file

$ rsync -avzh /root/rpmpkgs /tmp/backups/ # cp dir

# rsync --remove-source-files -avzhR /root/rpmpkgs /tmp/backups/

$ find ./ -type f -print0 | xargs -0 md5sum >> filename.md5

$ md5sum -c filename.md5 > check.log