Windows commonly used remote tools include SecureCRT, Putty, SSH Secure Shell, etc.
The SSH service supports a secure authentication mechanism, namely key authentication. The so-called key authentication actually uses a pair of encrypted strings, one is called the public key, and anyone can see its content and is used for encryption; the other is called the private key, Only the owner can see it for decryption. Ciphertext encrypted with the public key can be easily decrypted using the key, but it is very difficult to guess the key based on the public key. ssh's key authentication uses this feature. Both the server and the client each have their own public and secret keys.
Check if the firewall is turned off
[root@host ~]# service iptables status
Table: filter Chain INPUT (policy ACCEPT) num target prot opt source destination 1 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:4040 2 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:8080 3 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:4040
Chain FORWARD (policy ACCEPT) num target prot opt source destination
Chain OUTPUT (policy ACCEPT) num target prot opt source destination
turn off firewall
iptables: Setting chains to policy ACCEPT: filter [ OK ]
iptables: Flushing firewall rules: [ OK ]
iptables: Unloading modules: [ OK ]
[root@host ~]# service iptables status
iptables: Firewall is not running.
bin is the abbreviation of Binary, this directory stores the most frequently used commands.
arch chown df env gawk iptables-xml logger more ping rm sh taskset uname ypdomainname
awk cp dmesg ex grep iptables-xml-1.4.7 login mount ping6 rmdir sleep touch unicode_start zcat
basename cpio dnsdomainname false gtar kbd_mode ls mountpoint plymouth rpm sort tracepath unicode_stop
bash cut domainname fgrep gunzip kill lsblk mv ps rvi stty tracepath6 unlink
cat dash dumpkeys find gzip link mkdir netstat pwd rview su true usleep
chgrp date echo findmnt hostname ln mknod nice raw sed sync ulockmgr_server vi
chmod dd egrep fusermount ipcalc loadkeys mktemp nisdomainname readlink setfont tar umount view
Stored here are some core files used when starting Linux, including some connection files and image files.
This directory is used to store all configuration files and subdirectories required for system management.
The user's home directory. In Linux, each user has his own directory. Generally, the directory name is named after the user's account.
This directory stores the most basic dynamic link shared library of the system, and its function is similar to the DLL file in Windows. Almost all applications need to use these shared libraries.
The system provides this directory to allow users to temporarily mount other file systems. We can mount the CD-ROM drive on /mnt/, and then enter this directory to view the contents of the CD-ROM drive.
This directory is a virtual directory, it is a mapping of system memory, we can get system information by directly accessing this directory.
This directory is the home directory of the system administrator, also known as the super-authorized user.
s stands for Super User, which stores the system management program used by the system administrator.
This directory is unique to Redhat/CentOS. Selinux is a security mechanism, similar to the Windows firewall, but this mechanism is more complicated. This directory is used to store selinux-related files.
access booleans class context deny_unknown enforce load mls policy policyvers relabel user
avc checkreqprot commit_pending_bools create disable initial_contexts member null policy_capabilities reject_unknown status
This directory stores data that needs to be extracted after some services are started.
[root@localhost srv]# ls
[root@localhost srv]#
This directory is used to store some temporary files.
This is a very important directory. Many applications and files of the user are placed in this directory, similar to the program files directory under Windows.
-
/usr/bin: Applications used by system users.
-
/usr/sbin: The more advanced management programs and system daemons used by superusers.
-
/usr/src: The default directory for the kernel source code.
-
/var : This directory stores things that are constantly expanding. We are used to placing those frequently modified directories in this directory. Includes various log files.
total 279744
dr-xr-x--- 26 root root 4096 Apr 10 17:30 .
dr-xr-xr-x 26 root root 4096 Apr 10 16:54 ..
-rw-r--r-- 1 root root 0 Oct 19 10:06 10
-rw------- 1 root root 1037 Jul 11 2017 anaconda-ks.cfg
- When it is [ d ], it is a directory
- When it is [ - ], it is a file;
- If it is [ l ], it is represented as a link file;
- If it is [ b ], it means the interface device (random access device) that can be stored in the device file;
- If it is [ c ], it means the serial port device in the device file, such as keyboard, mouse (one-time read device).
The following characters are grouped by three, and they are all combinations of the three parameters of "rwx".
Bits 1-3 determine the permissions that the owner (the owner of the file) has on the file.
Bits 4-6 determine the permissions of the group (users in the same group of the owner) to have the file.
Bits 7-9 determine what permissions other users have on the file.