linux administration

Job Scheduling- As a system administrator some tasks are respective like backup. monitoring, log files.   To automate them below the commands or keys -at   -batch -crontab Crontab: to run some tasks automatically   to set a crontab for an user #crontab -e -u <user name> * * * * * /bin/echo "hello" A crontab file contains instructions to the cron deamon of the general form   "run this command at this time on this date" Cron examines entries once every minute Time mentioned here  field        allowed values  -----                   --------------  minutes               0-59  hour                  0-23  day of month     1-31  month     ...

Sudo is super user  a concept which is used to specify a customized  privilege commands to non-privileged  users. All sudo configuration is located under /etc/sudoers file.       To edit sudo configuration file use visudo command.             Add users using useradd command                                                  #useradd   sree                                 #useradd   sinu                     ...

File System Permissions- File System Permissions Umask :   umask is the value with this umask mask value kernel can identify who is going to create a file or directory. umask is the command to find out umask value root - umask 0022 normal -umask 0002 default permissions = maximum permissions-umask For a file :-      root      maximum permissions of a file 666                                           umask    022    (-)                                                   Normal User             maximum permissions of a file 666                                ...

User and  Group Administration - User(u)    -u Group(g) - Owner(own) Command Mode Practice These Steps:- vim  /etc/passwd : contains user information vim  /etc/shadow  : contains users password information vim  /etc/group : contains groups information cat /etc/passwd : to view total users info cat /etc/passwd | grep sam  (or) getent passwd sam : to view only sam users information cat /etc/shadow : to view passwords of all existing users cat /etc/shadow | grep sam (or) getent shadow sam : to view only sam users password cat /etc/group : to view all groups information cat /etc/group | grep hr (or) getent group hr : to view only hr group information. useradd <option> <username> -u : TO change uid syn: useradd -u <uidno> <username> ex: useradd -u 1000  sraviin -g : to add an user into a group useradd -g <groupname> <username> ex: useradd -g cyber sravn -G :to add an user in...

Linux Basic Commands-Memory related commands login to the unix/solaris server ip or host name Ex-   ip 10.1.21.1   host  usex10alg username: wesrg passwd         : ******* You will log in to the server. It will take you to default home_directory. - pwd it shows/prints the present working directory -ls -l gives listing of the files in present directory -cd .. takes you to previous directory mkdir <directory> will create directory  -mkdir -p /home/jb/j1/j2/j3 will create all the non-existing directories at a stretch -vi <file_name> opens file for reading/editing -cat <file_name> display contents of file -more <file_name> displays page by page contents of file -tail <file_name> shows last 10 lines of file use tail -f for continous update of file_name -head <file_name> shows first 10 lines of...