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*    *   *  *   *  command to be executed -     -    -   -  - |     |     |   |    | |     |     |   |    +----- day of week(0 - 6) (Sunday=0) |     |     |   +------- month (1 - 12) |     |     +--------- day of month (1 - 31) |     +----------- hour (0 - 23) +------------- min (0 - 59) Disable Mail Alert by Cron: 0 1 5 10 * /path/

You can share a bash screen using a utility call screen. yum install screen 1. Connect to a shell and type  issue command : screen 2. Hit Ctrl + a and then type < :multiuser on> 3. Other user type screen -x and connect to the session. 4. Press Ctrl + a

Enable Selected Commands Only (You have to set PermitRootLogin forced-commands-only  in order for this to work ) PermitRootLoginyes,no,without-password,forced-commands-only without-password : allow root login without password ( Using Keys ) forced-commands-only ( Allow only forced commands  with public key authentication and only if the command option has been specified which can be useful

Create .htaccess file with following AuthUserFile /home/username/.htpasswd<br></br> AuthGroupFile /dev/null<br></br> AuthName “Private Area”<br></br> AuthType Basic<br></br> require valid-user``` **create password file :** `httpasswd -bc /path/to/

How to forbid visitors to read files from a directory? Forbidding all files: deny from all Allow access from a certain IP address: order allow deny<br></br> deny from all<br></br> allow from <your_IP>``` In this case,

Change AllowOverride None to AllowOverride All from httpd.conf And then create a file named .htaccess in the folder you want to deny access and put the folowing : order deny,allow deny from all allow from

Find Directories: > find / -name -type d find / -iname -type d (Ignore Case) Find Empty Directories: > find / -type d -empty Find and count the result : > find / -type d -empty | wc -l Find and delete : > find / -type d -empty -exec rmdir {} ; Find and count Not matching criteria (non

Load balancing in Apache is pretty much simple. You need to have a load balancer, and more than one web server. Required module : mod_proxy_balancer This module is an Apache module available starting Apache 2.1. It enables an Apache to act as a load balancer. It can also

> Options -Indexes (disables directory listing) DirectoryIndex myfile.html (displays myfile.html) IndexIgnore *.gif *.jpg (Ignores files)

> $max)) { return FALSE; } else { return TRUE; } } ?> 5) && ($length <> 9)) { return FALSE; } return isDigits($code); case 'CA': if ($length <> 6) { return FALSE; } return preg_match ("/([A-z][0-9]){3}/", $code); } } ?>

> $result= mysql_query(“sql query”); if(mysql_num_rows($result)> 0) { $num_fields=mysql_num_fields($result); $headers = array(“Col1 Name”,”Col2 Name”,”Col3 Name”); $fp = fopen(‘php://output’, ‘w’); if ($fp && $result) { header(‘Content-Type: text/csv’); header(‘Content-Disposition: attachment; filename=”export.csv”‘); header(‘Pragma: no-cache’

> if (isset($_POST[‘submit’]) ) { foreach($_POST as $key=>$value) { $$key = $value; }

Open httpd.conf and set AllowOverride All restart apache web server and create a .htaccess file on the directory you want to block by ip : order deny,allowallow from x.y.z.a deny from all

Sync Files or folders to a remote host from local host : Rsync Syntax : #rsync options source destination -v, --verbose increase verbosity -q, --quiet decrease verbosity -c, --checksum always checksum -a, --archive archive mode. It is a quick way of saying you want recursion and want to preserve everything. -r, --recursive

> !/bin/sh Alert Email Address ALERT_EMAIL=”email address” ALERT_LEVEL=10 NO_MONITOR=”/dev/shm” #use pipe to separate multiple function calculate_usage() { while read raw_input; do used_space=$(echo $raw_input | awk ‘{ print $1}’ | cut -d’%’ -f1) partition=$(echo $raw_input | awk ‘{print $2}’) if [ $used_

** DSN: Service unavailable** RESOLUTION: set hostname other than localhost -------------------------------------------------------------------------------- -------------------------------------------------------------------------------- Relay host : open /etc/mail/sendmail.mc  and configure SMART HOST to your relay and remove the dnl at the front. vi /etc/mail/sendmail.mc dnl define(SMART_HOST', relayserver.domain.com')dnl make it look

dd if=/dev/cdrom of=~/cdrom_image.iso or mkisofs -o /tmp/cd.iso /tmp/directory

> rasterisk -x ‘database show’|grep -r “^/CF”

> 1. conf t 2. ip access-list {standard | extended} access-list-name 3. sequence-number acl 4. ip access-list resequence access-list-name starting-sequence-number increment eg. ip access-list resequence 111 100 15

Setting default group permission on a directory Set recursive sticky bit for the group on dir > chmod -R g+s /path/to/dir Recursively set group ownership of the directory > chown -R user:group /path/to/dir