20150905 after-school exercises

First, homework (exercise) content:

1. Summarize the detailed usage method of the task plan (at, crontab) on Linux system;

At

Command explanation:

One-time task execution

At:at time

At >

Exact time:

hh:mm

Blur Time:

now+ #UNIT

Noon

Midnight

Tomorrow

Example: 23:00 execute cat/etc/fstab;

650) this.width=650; "Style=" background-image:none;border-bottom:0px;border-left:0px;margin:0px;padding-left:0px ;p adding-right:0px;border-top:0px;border-right:0px;padding-top:0px; "title=" wpsc52a.tmp "border=" 0 "alt=" Wpsc52a.tmp "src=" http://s3.51cto.com/wyfs02/M01/72/BD/wKioL1XsYU_iGnzLAABPiwpT8o8051.jpg "height="/>

Example: Execute IP a command after 10 minutes;

650) this.width=650; "Style=" background-image:none;border-bottom:0px;border-left:0px;margin:0px;padding-left:0px ;p adding-right:0px;border-top:0px;border-right:0px;padding-top:0px; "title=" wpsc52b.tmp "border=" 0 "alt=" Wpsc52b.tmp "src=" http://s3.51cto.com/wyfs02/M02/72/BD/wKioL1XsYU-CWsavAABJK1urjFI757.jpg "height=" "/>

Job View:

At-l,atq

To delete a job that has not been run:

at-d [Job number]

Submit Job: Ctrl+d

Job results: Sent to the user in the form of a message.

Send and receive mail:

Netstat-antlpt | grep 25

The default send and receive messages are only made between users on this computer and only through loopback addresses.

Mail

Q: Exit

N: View Nth message

Mail user

650) this.width=650; "Style=" background-image:none;border-bottom:0px;border-left:0px;margin:0px;padding-left:0px ;p adding-right:0px;border-top:0px;border-right:0px;padding-top:0px; "title=" wpsc52c.tmp "border=" 0 "alt=" Wpsc52c.tmp "src=" http://s3.51cto.com/wyfs02/M00/72/BD/wKioL1XsYU_RDoZIAAA7liRJbxw921.jpg "height=" "/>"

650) this.width=650; "Style=" background-image:none;border-bottom:0px;border-left:0px;margin:0px;padding-left:0px ;p adding-right:0px;border-top:0px;border-right:0px;padding-top:0px; "title=" wpsc52d.tmp "border=" 0 "alt=" Wpsc52d.tmp "src=" http://s3.51cto.com/wyfs02/M01/72/BD/wKioL1XsYU_Qce3yAADH4XG-Kbk753.jpg "height=" "/>

Mail-s "title" User

650) this.width=650; "Style=" background-image:none;border-bottom:0px;border-left:0px;margin:0px;padding-left:0px ;p adding-right:0px;border-top:0px;border-right:0px;padding-top:0px; "title=" wpsc53d.tmp "border=" 0 "alt=" Wpsc53d.tmp "src=" http://s3.51cto.com/wyfs02/M02/72/BD/wKioL1XsYU_xmoCmAAA0gd000TM693.jpg "height="/>

echo "Content" | Mail-s "title" User

650) this.width=650; "Style=" background-image:none;border-bottom:0px;border-left:0px;margin:0px;padding-left:0px ;p adding-right:0px;border-top:0px;border-right:0px;padding-top:0px; "title=" wpsc53e.tmp "border=" 0 "alt=" Wpsc53e.tmp "src=" http://s3.51cto.com/wyfs02/M00/72/BD/wKioL1XsYVDA8ydCAAArAMXev4k184.jpg "height="/>

650) this.width=650; "Style=" background-image:none;border-bottom:0px;border-left:0px;margin:0px;padding-left:0px ;p adding-right:0px;border-top:0px;border-right:0px;padding-top:0px; "title=" wpsc53f.tmp "border=" 0 "alt=" Wpsc53f.tmp "src=" http://s3.51cto.com/wyfs02/M01/72/BD/wKioL1XsYVDBMf7AAADlSDhcg1w180.jpg "height=" 153 "/>

650) this.width=650; "Style=" background-image:none;border-bottom:0px;border-left:0px;margin:0px;padding-left:0px ;p adding-right:0px;border-top:0px;border-right:0px;padding-top:0px; "title=" wpsc540.tmp "border=" 0 "alt=" Wpsc540.tmp "src=" Http://s3.51cto.com/wyfs02/M02/72/BD/wKioL1XsYVCDReOMAAAO-5IA-Io978.jpg "height=" 6 "/>

Crontab

(1) Order Explanation:

Recurring Scheduled Tasks

(2) There are two types of crontab tasks

System crontab:/etc/crontab

User crontab: Defines a file with the same name as the user name in the/var/spool/cron/directory

Only one independent task can be defined per line

# Example of Job definition:

#.----------------Minute (0-59)

# | .-------------Hour (0-23)

# |  | .----------Day of Month (1-31)

# |  |  | .-------month (1-12) OR jan,feb,mar,apr ...

# |  |  |  | .----Day of Week (0-6) (sunday=0 or 7) or Sun,mon,tue,wed,thu,fri,sat

# |  |  |  | |

# * * * * * * user-name command to be executed

Point in time:

Minute hour day month week

Time notation:

1. Each time bit should be evaluated using its available valid range: * is used for all valid values.

17 * * * *

8 9 * * *

2.*/#, at the corresponding time bit valid value on every # time unit once

*/3 * * * * * run every 3 minutes

0 */3 * * * run every 3 hours

* */3 * * * * run every 3 hours every minute

(3) Continuous point-in-time

20 3 * * 1-6 weekly 1 to 6, 3:20

4. Discrete time points:

20 3 * * 2,4,6 per week 2,4,,6. 3:20 Execute Once

User-defined: crontab command

-L: Lists all tasks that have been defined

-E: Open the Edit Interface definition task

-R: Remove All Tasks

2, every Monday to Saturday 3:20 A.M., run the CP command to archive the/etc/directory, storage location is/BACKUPS/ETC-YYYY-MM-DD;

3 * * 1-6/bin/cp-a/etc/backups/etc-$ (date + '%y-%m-%d ')

3 * * 1-6/bin/tar-cvf/backups/etc-$ (date + '%y-%m-%d '). tar/etc

650) this.width=650; "Style=" background-image:none;border-bottom:0px;border-left:0px;margin:0px;padding-left:0px ;p adding-right:0px;border-top:0px;border-right:0px;padding-top:0px; "title=" wpsc541.tmp "border=" 0 "alt=" Wpsc541.tmp "src=" http://s3.51cto.com/wyfs02/M02/72/C1/wKiom1XsXyiT5qd7AABweZC_69g591.jpg "height="/>

3, every Sunday 2:30 A.M., run the CP command to backup the/etc/fstab file, the storage location is/BACKUP/FSTAB-YYYY-MM-DD-HH-MM-SS;

2 * * 7/bin/cp-a/etc/fstab/backup/fstab-$ (date + '%y-%m-%d-%h-%m-%s ')

650) this.width=650; "Style=" background-image:none;border-bottom:0px;border-left:0px;margin:0px;padding-left:0px ;p adding-right:0px;border-top:0px;border-right:0px;padding-top:0px; "title=" wpsc542.tmp "border=" 0 "alt=" Wpsc542.tmp "src=" http://s3.51cto.com/wyfs02/M00/72/BD/wKioL1XsYVDyOl8KAABjNYem_DY711.jpg "height=" "/>"

4, every night 12 o'clock, get all the lines in the/proc/meminfo file starting with S or M, appended to the/statistics/meminfo.txt file, and the daily message before, to add a similar =============== separator line;

1 * * * echo ' =================================== ' egrep ' ^[sm] '/proc/meminfo ' >>/statistics/meminfo.txt

650) this.width=650; "Style=" background-image:none;border-bottom:0px;border-left:0px;padding-left:0px; padding-right:0px;border-top:0px;border-right:0px;padding-top:0px; "title=" wpsc553.tmp "border=" 0 "alt=" Wpsc553.tmp "src=" http://s3.51cto.com/wyfs02/M01/72/BD/wKioL1XsYVHgaucAAABTotd4MSo938.jpg "height=" "/>:

20150905 after-school exercises