Basic System Commands
1 PATH environment variable
echo the PATH $
2 common commands
date - to view the system clock
is often used when the file name
% F. 2019-8-26
% D 08/26/19
% H
% m% M
% S
Clock hardware clock hwclock--
cal look at the calendar
hwclock -s // system clock with the hardware clock synchronization, clock synchronization for hardware
extensions: ntp server
yum install ntp
to modify /etc/ntp.conf files, to achieve the client and server time synchronization;
pwd cd
. Contents: the current directory
.. the parent directory
~ home directory
- a directory
basedname
dirname
PWD OLDPWD
ls
involves a lot of file attribute information
-i inode information (file system-related)
the -I file type file permissions (your main group belongs to other special permission bits) of hard links relevant to your main set of files (directory) size Mtime file (directory) name
- plain text file
d directory file
l soft link is connected document file ------------------------------- character length
s ------------------------------- socket file number of this device is the master device
b block device file ----- -------------------------- number of this device is the master device
c character device file stream file device
p pipe file
view files file specific file type
plain text files are displayed as ASCALL file
start time information of view file
touch -C modifying
atime - access time - the time the file is read or executed
mtime - change time - file status change time
ctime - modify time - file contents are modified
cat tac
view the file contents
cat can combine multiple lines of input redirection
-n
Other common command
who w whoami view the current user login information
whereis
view commands absolute path
to view the man's help documentation path
Which
hatis
the shutdown the HALT the init 6 reboot the init 0 poweroff
the shutdown now // immediately shut down
shutdown -r now // immediately restart
shutdown 17 : 00 // off at the 17:00
shutdown +5 // shutdown command five minutes after
shutdown -c // cancel the shutdown command
shutdown call is poweroff
the HALT directly off --halt
poweroff - will do the inspection process and powering down
reboot - restart
init 0 / init 6