• systemd management using systemctl and journalctl to check systemd logs


    systemd is like the service manager for your Centos and other modern Linux distributions (including Debian/Mint/Ubuntu) allows you to enable services, stop them, restart them, check their status and even reboot your system. The key commands or arguments you will use with systemctl are the following: Unit Commands: list-units [PATTERN...] List loaded units &nbs........
  • Asterisk iptables block bruteforce attacks howto with fail2ban


    yum -y install fail2ban vi /etc/fail2ban/jail.conf [asterisk-tcp] enabled = true filter = asterisk action = iptables-multiport[name=asterisk-tcp, port="5060,5061", protocol=tcp] sendmail-whois[name=Asterisk, dest=you@example.com, sender=fail2ban@example.com] logpath = /var/log/asterisk/messages maxret........
  • Sendmail Gmail.com blocking


    relay=alt4.gmail-smtp-in.l.google.com. [74.125.136.26], dsn=4.0.0, stat=Deferred: 421-4.7.0 [ 10] Our system has detected an unusual rate of This is strange because the mail server IP is not blacklisted anywhere and the IP itself has not been used for years and this server is clean and has only sent a few e-mails to gmail.com in its entire time. I wonder if this is a legacy block on a whole range of IPs as punishment for others in the block........
  • pxe-32 tftp open timeout


    pxe-32 tftp open timeout The solution was to enable tftp in xinetd with "chkconfig tftp on". See the troubleshooting below: chkconfig --list NetworkManager 0:off 1:off 2:off 3:off 4:off 5:off 6:off acpid 0:off&n........
  • stat=Deferred: 451-Non-existent domain mailserver.com


    Jul 11 15:20:58 tor sendmail[9617]: r6AKjOD07: to= mailserver.com was the hostname of the server, sendmail sends this by default and many mailservers will reject mail to a hostname that does not resolve or exist. The easiest way is just to change the hostname and make sure it does resolve to something. I read there is a way in sendmail.mc to manually set a hostname but I never got it working: vi /etc/mail/sendmail.mc define(`confDOMAIN........
  • How to log all PHP based E-mails for abuse


    Step #1 - Create Wrapper Script vi /usr/local/bin/phpsendmail #!/usr/bin/php ........
  • Enable SPAMASSASSIN on Postfix in 5 minutes


    Centos 5 Postfix and SPAMASSASSIN Tutorial yum install spamassassin chkconfig spamassassin on vi /etc/mail/spamassassin/local.cf ############## #required_hits 5 #report_safe 0 #rewrite_header Subject [SPAM] #5 is the least restrictive (means only the most obvious SPAM is caught. 0 is obviously the most restrictive/sensitive and would have lots of false positives require........
  • Understanding /etc/aliases from sendmail when using with postfix or other MTA's


    understanding /etc/aliases *remember to apply changes you need to run "newaliases" after editing /etc/aliases one thing I don't get is that it doesn't allow you to specify the whole e-mail address on the left-hand side eg: yourfullemail@domain.com: someotheremail@domain.com postalias: warning: /etc/aliases, line 109: name must be local (if you try the above) It works more like this: your........
  • Linux Centos/RHEL can't find php/apache/httpd/mysql/ftp/exim/sendmail ?


    I wasted a lot of time wondering why I could never find those packages. Check the /etc/yum.conf file and at the bottom look for the "exclude=" line. Below is what I found in mine exclude=apache* httpd* mod_* mysql* MySQL* da_* *ftp* exim* sendmail* php* bind-chroot* Just remove those entries or uncomment that line and you'll get access to the missing applications.........
  • PHP cannot access /usr/bin/openssl


    PHP cannot access /usr/bin/opensslI have verified the username that runs the process is able to access /usr/bin/openssl and it does exist but the PHP script is saying it doesn't exist: [code:1:1fd0f3abbe] if (!file_exists($OPENSSL)) { //echo "ERROR: OPENSSL $OPENSSL not foundn"; }[/code:1:1fd0f3abbe] I don't get itI can clearly see the contents of /usr/bin by using the PHP system fu........
  • Latest Articles

  • Linux How To Create A RamDisk
  • mdadm force resync when resync=PENDING solution
  • Proxmox Breaks Storage/LVM Backing If Killing QEMU-IMG
  • Proxmox trying to acquire lock... TASK ERROR: can't lock file '/var/lock/qemu-server/lock-102.conf' - got timeout
  • Debian 9 SSH root password authentication failure password not working problem / solution
  • QEMU / KVM How To Manually Create Basic Virtual Machine VM
  • Linux wlan0 check all wireless clients
  • PHP Issues With Decoding Strange Smart Quotes And Non-Standard ASCII Characters
  • /etc/iproute2/rt_tables default settings file in Linux Centos 6,7 and most other NIX's
  • bind named error solutions named[2169]: error (no valid DS) resolving / error (broken trust chain) resolving / : error (no valid RRSIG) resolving 'com/DS/IN':
  • iptables how to log ALL dropped incoming packets
  • How To Edit Linux Based NM Network Manager Connection Settings Without GUI
  • Linux Disable IPV6 Centos / Debian / Mint Howto
  • Linux use growisofs to burn a larger file on a BD-R / Bluray Disc
  • Linux partprobe/partx cannot access last and 4th partition
  • DRBD Errors Caused By Physical Corruption
  • mdadm: add new device failed for /dev/sdb4 as 3: Invalid argument solution
  • Linux named / bind how to dump, view and clear the cache!
  • Centos 6 / 7 / 8 How To Change Default nameservers in /etc/resolv.conf when using DHCP / dhclient
  • Adobe Acrobat Reader for Linux to use and view XFA Fillable Forms