Linux OPS Practice-September 5, 2015 Course assignments

First, summarize the detailed usage method of the task plan (at, crontab) on Linux system;

1. At command:

To host a job that runs in the future time:

Support for using job queues:

The default is a queue;

At [option] ... Time

Time:

(1) Absolute time

HH:MM,

Mmdd[cc]yy, Mm/dd/[cc]yy, dd.mm.[cc]yy or [cc]yy-mm-dd

Tomorrow

(2) Relative time

now+ #UNIT

Minute, hour, day, week

(3) Blur time

Midnight

Noon

Teatime

Common options:

-Q queue:at Job queue;

-f/path/from/somefile: Reads the job to be run from the specified file;

-L: View a list of such running jobs in the job queue; equivalent to using the ATQ command;

-C At_job_num: Look at the contents of the running job;

-D: Delete the specified job; equivalent to ATRM

Batch

The system chooses to run the specified task when the resource is more idle;

2. Crontab: Recurring Task plan

Daemon: Crond

There are two types of recurring tasks:

(1) System cron task; There is no default running user identity, so you need to specify the additional runner;

/etc/crontab

Vim command

# 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

7 fields:

Top 5 fields: Point in time

User-name: Run the task as a user

command to being executed: to run a task

(2) User Cron Task: Submitted by a user, the default is to run as the submitter, so there is no need to specify the additional runner;

/var/spool/cron/username

VIM command; not recommended

crontab Command: Recommended

# 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

# | | | | |

# * * * * * command to be executed

5 Time points:

Minutes: valid value range 0-59;

Hours: 0-23

Day: 1-31

Month: 1-12

Weeks: 0-7

Note: The date of the month and the number of weeks, not recommended to use at the same time;

For example:

6 * * * *

Time notation:

*: Each time point in the valid value range of the time point;

-: A specific continuous time range, 3-7

,: A discrete point in time, 3,5,7

/#: The amount of time in a valid time frame, for specifying the frequency;

1-30/4, */4

5 */3 * * */bin/echo "howdy"

5 7 * * 1-5/bin/echo "Howdy"

crontab command:

crontab [-u user] [-l |-r |-e]

-u User: Not to manage your own cron task, but to specify the target user's cron task; Root has the ability to manage other users ' cron tasks; default management of their own;

-l:list, list the tasks;

-r:remove to remove all tasks;

-e:edit, edit, open a default editor for the current shell session to edit the cron task table;

Complementary tools: Anacron:

Attention:

(1) If you do not want to receive notification messages for task execution results:

COMMAND >/dev/null

COMMAND &>/dev/null

(2) for crontab file,% has a special function, if the command will appear in the%, remember to escape, or use single quotation marks to its reference;

(3) Crontab's path variable is not exactly the same as the user's variable, so it is recommended that the task in cron use an absolute path

/root/bin/a.sh

Second, every Monday to Saturday 3:20 A.M., run the CP command to save the/etc/directory for archiving, storage location is/backups/etc-yyyy-mm-dd;

[Email protected] ~]# mkdir/backups

[Email protected] ~]# CRONTAB-E

* * 1-6/bin/tar-czvf/backups/etc.$ (date +%y-%m-%d) tar.gz/etc/

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Third, 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;

[Email protected] ~]# crontab E

* * 7/BIN/CP-/etc/fstab/backup/fstab-$ (date +%y-%m-%d-%h-%m-%s)

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Four, every night 12 o'clock, get all lines in the/proc/meminfo file that begin with S or M, append to the/statistics/meminfo.txt file, and precede the daily message with a similar =============== separator line;

[Email protected] ~]# crontab E

XX * * */bin/echo =============== >/statistics/meminfo.txt&&/bin/egrep "^s|^m"/proc/meminfo >>/ Statistics/meminfo.txt

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Linux OPS Practice-September 5, 2015 Course assignments