Start
Motherboard BIOS -- Grub -- kernel -- run-level results
Running level
0 Shutdown
1 single user (Repair Mode)
2. No NFS Mode
3. Full mode without image Interface
4. Custom Mode
5. Full mode with image Interface
6. Restart
Add password to Grub
Cd/boot/grub
Vi menu. lst
Add a row to timeout
Password
Save and exit
Grub-install -- no-floppy/dev/sda # Make the modified grub start content take effect
Modify the running level
Init number
Service
Chkconfig -- list # list service statuses (started)
Service name running status
Sshd 0: Disable 1: Disable 2: Enable 3: Enable 4: Enable 5: Enable 6: Disable
Modify
Chkconfig -- level 1 sshd on
The sshd service is started by default at runlevel 1.
Chkconfig -- level 1 sshd off
The sshd service is disabled by default at runlevel 1.
If no running level is set, the 2345 running level status is adjusted.
Chkconfig sshd on
Chkconfig sshd off
Xinetd is a special service.
For example, enable the telnet service.
First let the ekrb5-telnet be turned on
Xinetd is enabled.
If one of them is not enabled, the operation fails.
All xinetd-based services: The same as the method for enabling telnet
Restart service
Service name restart
Stop Service
Service name stop
Start the service
Service name start
* The firewall will affect services and disable the firewall.
Chkconfig iptables off
Service iptables stop
* Telnet cannot be used as the root user to log on directly. If you use a common user to log on, run su-to change to the root user.
/Etc/rc. d/rc. local
The last service executed when the system starts. It exists by default and is generally not canceled.
Programs and processes
View the programs currently running in the system
Ps-ax
-A for all users
-X expanded
Process number running Terminal status (S wait, s sleep, T is to stop the program, Z is a zombie program, R is running) How long to run the command
PID TTY STAT TIME COMMAND
1? Ss 0: 01/sbin/init
Top System Process Monitor
Top-09:53:35 (system time) up (system running time), 5 users (number of currently logged on users), load average: 0.00, 0.00, 0.01 (system load value)
Tasks: 197 total (number of system processes), 1 running (number of running), 196 sleeping (number of sleep), 0 stopped (stop not quit), 0 zombie (botnet)
Cpu (s): 0.2% us, 0.3% sy, 0.0% ni, 99.2% id (CPU remaining), 0.3% wa, 0.0% hi, 0.0% si, 0.0% st
Mem: 2980496 k total (total physical memory), 1023280 k used (maximum memory used), 1957216 k free (minimum idle), 132928 k buffers (Cache used for the Network)
Swap: 5079032 k total (total virtual memory), 0 k used (maximum virtual memory usage), 5079032 k free (minimum virtual memory idle ), 488952 k cached (memory ready for quick use)
Process No. User status CPU usage memory usage Run Time Command
Pid user pr ni virt res shr s % CPU % mem time + COMMAND
2869 root 20 0 2660 1120 R 848 1.0. 25 top
Memory computing
Maximum memory used-memory ready for quick use = memory used by the System
System load value (the usage of a computer is 10.00)
Every 3 minutes every 5 minutes every 15 minutes
Load average (average): 0.00, 0.00, 0.01
Close Process
Kill-9 process no.
-9 Force Execution
Killall-9 process name
-9 Force Execution
Scheduled tasks
Backup System users are required at every day
1. the/etc/passwd/etc/shadow/etc/group file to be backed up by the System user is the system's all user information files.
2. The/home directory contains the file directory of the System user.
Creation Method: copy the files and directories to the/sysbak directory at every day.
Crond Service
Crondtab-e: Enter scheduled task orchestration
Minute hour day month week command
0 1 * mkdir-p/sysbak
The time requirement must be that the table can appear.
Run every minute
*/1 ****
Hourly
0 */1 ***
Every day
0 0 */1 **
Monthly
0 0 0 */1 *
Every week
0 0 0 0 */1
Interval
1, 30 ****
Continuous
1-30 ****
0-7. Both 0 and 7 are sundays.
After the orchestration, restart the crond service.
Service crond restart
Date: view system time
Date-s 0059 modification time
This article is from the blog "Wang Dao-Xu zhongzhi (MakeWong )".