• Cisco DHCP Snooping Relay Setup Information


    Switch#show ip dhcp snooping Switch DHCP snooping is disabled DHCP snooping is configured on following VLANs: 1 Insertion of option 82 is enabled circuit-id format: vlan-mod-port remote-id format: MAC Option 82 on untrusted port is not allowed Verification of hwaddr field is enabled Interface&nb........
  • gmail.com address failing in Postfix


    Aug 10 01:11:54 mailserver postfix/smtp[6180]: 020AE17C2BD1: to=, relay=none, delay=0.29, delays=0.28/0/0/0, dsn=5.4.4, status=bounced (Host or domain name not found. Name service error for name=gmail.con type=A: Host not found) A user complained that their e-mails weren't being delivered but they actually made a small typo and used gmail.con so it wasn't working as expected of course........
  • 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........
  • 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........
  • MySQL NEVER delete ib_logfile0 or ibdata1 or you'll lose data


    don't delete /var/lib/mysql/ib_logfile0 or ibdata1 or mysql won't restart I didn't realize they were internal and not part of replication like the relay files! /usr/libexec/mysqld: ready for connections. Version: '4.1.22-log' socket: '/var/lib/mysql/mysql.sock' port: 3306 Source distribution 110127 16:31:00 [Note] /usr/libexec/mysqld: Normal shutdown 110127 16:31:00 InnoDB: Starting shutdown...........
  • Postfix/Any Email Server check for Open Relay


    The first thing you need to remember is not to check from the same host/server itself. This is a silly mistake I made, the reason is that many mailservers and especially postfix are configured to allow relaying from the localhost/same host. If you do that you'll get a false positive. *Make sure you test from another host/system than the mail server itself! telnet yourmailserverhost.com 25 220 Courier (FreeBS........
  • email server messsages rejected without reverse DNS DNS check failure Client host rejected: cannot find your reverse hostname Cannot resolve PTR record


    Basically you should always be 100% sure that whatever IPyour mail server sends out with has reverse DNS/PTR records. Remember that unless you own your IPs then you won't be able to set your own reverse DNS. Even if you were to create a reverse PTR record on your DNS servers it will be ignored. Reverse DNS is queried to pre-assigned DNS servers of your ISP, so therefore you'll need to contact your ISP/Colo/Hosting provider to do a reverse DNS entry. If you don't have........
  • 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........
  • Latest Articles

  • LXC Containers LXD How to Install and Configure Tutorial Ubuntu Debian Mint
  • GlusterFS HowTo Tutorial For Distributed Storage in Docker, Kubernetes, LXC, KVM, Proxmox
  • Ubuntu Mint audio output not working pulseaudio "pulseaudio[13710]: [pulseaudio] sink-input.c: Failed to create sink input: too many inputs per sink."
  • How To Shrink Dynamically Allocated VM QEMU KVM VMware Disk Image File
  • How To Enable Linux Swapfile Instead of Partition Ubuntu Mint Debian Centos
  • 404 Not Found [IP: 151.101.194.132 80] apt update Debian 11 Bullseye Solution The repository 'http://security.debian.org bullseye/updates Release' does not have a Release file.
  • WARNING: Can't download daily.cvd from db.local.clamav.net freshclam clamav error solution
  • (firefox:9562): LIBDBUSMENU-GLIB-WARNING **: Unable to get session bus: Failed to execute child process "dbus-launch" (No such file or directory) Solution
  • Debian Mint Ubuntu Which Package Provides missing top, ps and w Solution
  • Vbox Virtualbox DNS NAT Network Mode NOT working
  • Docker Tutorial HowTo Install Docker, Use and Create Docker Container Images Clustering Swarm Mode Monitoring Service Hosting Provider
  • Zoom Password Error 'That passcode was incorrect' - Solution Wrong Passcode Wrong Meeting Name
  • How To Startup and Open Remote/Local Folder/Directory in Ubuntu Linux Mint automatically upon login
  • How To Reset Windows Server Password 2019, 2022, 7, 8, 10, 11 Recovery and Removal Guide Using Linux Ubuntu Mint Debian
  • How To Create OpenVPN Server for Secure Remote Corporate Access in Linux Debian/Mint/Ubuntu with client public key authentication
  • HongKong VPS Server, Cloud, Dedicated Server, Co-Location, Datacenter The Best Guide on Hong Kong, China Internet IT/Computing
  • ssh-keygen id_rsa private key howto remove the passphrase so no password is required and no encryption is used
  • Package wget is not available, but is referred to by another package. This may mean that the package is missing, has been obsoleted, or is only available from another source. E: Package 'wget' has no installation candidate. Solution
  • tag#4 FAILED Result: hostbyte=DID_OK driverbyte=DRIVER_SENSE tag#4 Sense Key : Illegal Request [current] res 40/00:b4:98:02:00/00:00:00:00:00/40 Emask 0x10 (ATA bus error) solution
  • Wazuh Install and Configuration Howto Tutorial Guide for Monitoring Agents