Frequently Asked Questions About Linux / UNIX » Openbsd http://www.cyberciti.biz/faq Every answer asks a more beautiful question. Fri, 03 Feb 2012 22:38:32 +0000 en hourly 1 http://wordpress.org/?v=3.3.1 Linux / Unix: Disable OpenSSH Host Key Checkinghttp://www.cyberciti.biz/faq/linux-appleosx-howto-disable-ssh-host-key-checking/ http://www.cyberciti.biz/faq/linux-appleosx-howto-disable-ssh-host-key-checking/#comments Fri, 30 Dec 2011 11:37:09 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11310 I've a remote Unix server running with OpenSSH remote login service. The openssh is configured for passwordless login using ssh keys. Our ISP allows to boot all Linux servers into the rescue mode. It allow us to bring a server online remotely in order to troubleshoot system problems that would normally only be resolved by an OS Reload (such as accidentally deleting files or wrong firewall configurations blocking ssh access). When server boots into a remote rescue mode I can connect using SSH. They SSH keys will not be the same in the rescue mode so I get key mismatch messages as SSH keys are re-generated on each boot:
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @ @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY! Someone could be eavesdropping on you right now (man-in-the-middle attack)! It is also possible that the RSA host key has just been changed. The fingerprint for the RSA key sent by the remote host is e1:9b:5c:16:a6:cd:11:10:3a:cd:1b:a2:16:cd:e5:1c. Please contact your system administrator. Add correct host key in /home/user/.ssh/known_hosts to get rid of this message. Offending key in /home/user/.ssh/known_hosts:1 RSA host key for www.cyberciti.biz has changed and you have requested strict checking. Host key verification failed.
How do I ignore OpenSSH hos key checking from my Apple OS X laptop while login using the ssh?]]> http://www.cyberciti.biz/faq/linux-appleosx-howto-disable-ssh-host-key-checking/feed/ 2 SSH: Agent Admitted Failure To Sign Using The Key Error And Solutionhttp://www.cyberciti.biz/faq/unix-appleosx-linux-bsd-agent-admitted-failuretosignusingkey/ http://www.cyberciti.biz/faq/unix-appleosx-linux-bsd-agent-admitted-failuretosignusingkey/#comments Sat, 17 Sep 2011 04:34:19 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11083 I've recently regenrated and uploaded a new public ssh-key using the ssh-copy-id command. Now I'm getting the following error:
ssh root@server3 Agent admitted failure to sign using the key. root@server3's password:
How do I fix this problem?]]> http://www.cyberciti.biz/faq/unix-appleosx-linux-bsd-agent-admitted-failuretosignusingkey/feed/ 1 OpenBSD: Install Firefox Web Browserhttp://www.cyberciti.biz/faq/openbsd-install-firefox-web-browser/ http://www.cyberciti.biz/faq/openbsd-install-firefox-web-browser/#comments Sun, 17 Jul 2011 14:01:44 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=10886 How do I install Mozilla Firefox which is a free and open source web browser under OpenBSD operating systems?]]> http://www.cyberciti.biz/faq/openbsd-install-firefox-web-browser/feed/ 0 No xauth Program; Cannot Forward With Spoofing Error and Solutionhttp://www.cyberciti.biz/faq/linux-unix-appleosx-noxauth-program-cannot-forward-with-spoofing/ http://www.cyberciti.biz/faq/linux-unix-appleosx-noxauth-program-cannot-forward-with-spoofing/#comments Wed, 15 Jun 2011 19:11:41 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=10704 I want to use my local machine as the X server over ssh. But when I try to run ssh -X -v user@server1.example.com to the remote machine, I get the following error: debug1: Remote: No xauth program; cannot forward with spoofing How do I fix this problem and use X over ssh?]]> http://www.cyberciti.biz/faq/linux-unix-appleosx-noxauth-program-cannot-forward-with-spoofing/feed/ 0 Linux / UNIX: Kill Unresponsive SSH Sessionhttp://www.cyberciti.biz/faq/openssh-linux-unix-osx-kill-hung-ssh-session/ http://www.cyberciti.biz/faq/openssh-linux-unix-osx-kill-hung-ssh-session/#comments Wed, 05 Jan 2011 12:09:06 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=9686 Sometime my ssh session just stops working because of the internet connection problem. I tried pressing CTRL+Z and CTRL+C to terminate session, but failed to work. How do I properly kill a hung SSH session without killing my local terminal or using kill command?]]> http://www.cyberciti.biz/faq/openssh-linux-unix-osx-kill-hung-ssh-session/feed/ 1 Linux / UNIX: Speed up SSH X11 Forwardinghttp://www.cyberciti.biz/faq/speeding-up-ssh-x11-forwarding-with-unix-osx-linux-bsd/ http://www.cyberciti.biz/faq/speeding-up-ssh-x11-forwarding-with-unix-osx-linux-bsd/#comments Wed, 05 Jan 2011 11:51:00 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=9679 I've an CentOS based server and Ubuntu based desktop pc. I'm connecting to my CentOS using ssh X11 forwarding feature. However, speed over the Internet is pretty slow for certain apps such as VMWare console. How do I speed up OpenSSH X11 forwarding using Linux / UNIX desktop system?]]> http://www.cyberciti.biz/faq/speeding-up-ssh-x11-forwarding-with-unix-osx-linux-bsd/feed/ 2 Linux KVM: OpenBSD Guest Hangs At Starting tty Flagshttp://www.cyberciti.biz/faq/kvm-virtualization-openbsd-guest-hangs-at-starting-tty-flags/ http://www.cyberciti.biz/faq/kvm-virtualization-openbsd-guest-hangs-at-starting-tty-flags/#comments Thu, 15 Jul 2010 20:25:49 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=8337 OpenBSD version 4.5 and above made changes in kernel which prevents booting OpenBSD using KVM technology. OpenBSD 4.4 runs with mbbios enabled. However, due to some sort of bug in KVM it does not boots. The workaround is to disable mpbios. This may or may not happen with your installation. ]]> http://www.cyberciti.biz/faq/kvm-virtualization-openbsd-guest-hangs-at-starting-tty-flags/feed/ 0 KVM virt-install: Install OpenBSD As Guest Operating Systemhttp://www.cyberciti.biz/faq/kvmvirtualization-virt-install-openbsd-unix-guest/ http://www.cyberciti.biz/faq/kvmvirtualization-virt-install-openbsd-unix-guest/#comments Thu, 15 Jul 2010 19:36:26 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=8314 OpenBSD is a UNIX like system based on Berkeley Software Distribution (BSD). It was forked form NetBSD and created by Theo de Raadt in 1995. OpenBSD is famous for quality code and documentation without compromising position on software licensing. OpenBSD is also well know for focus on security features such as Memory protection, cryptography, randomization and much more in default base installation. ]]> http://www.cyberciti.biz/faq/kvmvirtualization-virt-install-openbsd-unix-guest/feed/ 0 OpenBSD: Setup Serial Consolehttp://www.cyberciti.biz/faq/openbsd-connect-serial-console/ http://www.cyberciti.biz/faq/openbsd-connect-serial-console/#comments Tue, 06 Jul 2010 12:13:55 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=8167 How do I enable console redirection under OpenBSD so that I can see my remote server boot information and any diagnostic information that is normally printed to the screen? I've already enabled serial ports in my server BIOS and wired them up. How do I configure and access OpenBSD UNIX x86/amd64 server over serial console?]]> http://www.cyberciti.biz/faq/openbsd-connect-serial-console/feed/ 0 OpenBSD: Static Routing Configurationhttp://www.cyberciti.biz/faq/howto-setup-static-routes-on-openbsd-unix-networking/ http://www.cyberciti.biz/faq/howto-setup-static-routes-on-openbsd-unix-networking/#comments Tue, 06 Jul 2010 11:42:17 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=8151 I know how to setup static routing under Linux and FreeBSD operating systems. But, how do you setup static routing under OpenBSD operating systems?]]> http://www.cyberciti.biz/faq/howto-setup-static-routes-on-openbsd-unix-networking/feed/ 3 Force SSH Client To Use Given Private Key ( identity file )http://www.cyberciti.biz/faq/force-ssh-client-to-use-given-private-key-identity-file/ http://www.cyberciti.biz/faq/force-ssh-client-to-use-given-private-key-identity-file/#comments Mon, 17 May 2010 14:54:16 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=7442 Recently, my desktop hard disk crashed. So I reinstalled Linux and created a new set of private RSA keys for authentication. However, two of my remote UNIX servers still uses old DSA keys. I do not remember root password for those servers. I do have backup of private and public DSA keys and currently stored in /backup/home/user/.ssh/id_dsa and /backup/home/user/.ssh/id_dsa.pub. How do I force my ssh clients to use identity file /backup/home/user/.ssh/id_dsa to get back to my remote UNIX servers?]]> http://www.cyberciti.biz/faq/force-ssh-client-to-use-given-private-key-identity-file/feed/ 2 HowTo: OpenBSD Mount an NTFS File Systemhttp://www.cyberciti.biz/faq/openbsd-mount-microsoft-ntfs-filesystem-command/ http://www.cyberciti.biz/faq/openbsd-mount-microsoft-ntfs-filesystem-command/#comments Sat, 01 May 2010 22:16:56 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=10474 I'm dual booting my Windows XP system with OpenBSD. How do I mount an NTFS file system under OpenBSD operating systems?]]> http://www.cyberciti.biz/faq/openbsd-mount-microsoft-ntfs-filesystem-command/feed/ 0 OpenBSD: Change Passwordhttp://www.cyberciti.biz/faq/openbsd-changing-user-password/ http://www.cyberciti.biz/faq/openbsd-changing-user-password/#comments Sun, 06 Dec 2009 22:16:01 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=9546 How do I change root user or any other user account password under OpenBSD operating systems?]]> http://www.cyberciti.biz/faq/openbsd-changing-user-password/feed/ 0 Ksh Read a File Line By Line ( UNIX Scripting )http://www.cyberciti.biz/faq/ksh-read-file/ http://www.cyberciti.biz/faq/ksh-read-file/#comments Fri, 20 Nov 2009 14:30:30 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=5797 How do I read a file line by line using KSH shell scripting under UNIX like operating systems?]]> http://www.cyberciti.biz/faq/ksh-read-file/feed/ 8 Firefox: Add a Trusted CAhttp://www.cyberciti.biz/faq/firefox-adding-trusted-ca/ http://www.cyberciti.biz/faq/firefox-adding-trusted-ca/#comments Mon, 31 Aug 2009 09:29:59 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=5147 The default Firefox comes with certificates from well-known commercial CAs. My ISP is also CA and Firefox cannot verified it because the CA is not recognized. How do I force Firefox to accept my ISPs certificate?]]> http://www.cyberciti.biz/faq/firefox-adding-trusted-ca/feed/ 6 UNIX Get An Alert When Disk Is Fullhttp://www.cyberciti.biz/faq/mac-osx-unix-get-an-alert-when-my-disk-is-full/ http://www.cyberciti.biz/faq/mac-osx-unix-get-an-alert-when-my-disk-is-full/#comments Thu, 13 Aug 2009 08:03:00 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=4745 I want to get an alert when my disk is full under UNIX and Mac OS X? How do I set a a specified threshold and run the script via cron?]]> http://www.cyberciti.biz/faq/mac-osx-unix-get-an-alert-when-my-disk-is-full/feed/ 24 BSD PF Firewall Block FTP Bruteforce Attackshttp://www.cyberciti.biz/faq/freebsd-openbsd-pf-stop-ftp-bruteforce-attacks/ http://www.cyberciti.biz/faq/freebsd-openbsd-pf-stop-ftp-bruteforce-attacks/#comments Thu, 13 Aug 2009 07:16:13 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=4740 I see lots of failed FTP login attempts in my log file. How do I stop FTP bruteforce attack? What should I do to solve this problem under FreeBSD 7.x server operating systems? ]]> http://www.cyberciti.biz/faq/freebsd-openbsd-pf-stop-ftp-bruteforce-attacks/feed/ 5 Shell Script While Loop Exampleshttp://www.cyberciti.biz/faq/shell-script-while-loop-examples/ http://www.cyberciti.biz/faq/shell-script-while-loop-examples/#comments Thu, 16 Jul 2009 07:33:20 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=4490 Can you provide me a while loop control flow statement shell script syntax and example that allows code to be executed repeatedly based on a given boolean condition?]]> http://www.cyberciti.biz/faq/shell-script-while-loop-examples/feed/ 10 OpenBSD: Find Out Memory RAM Sizehttp://www.cyberciti.biz/faq/openbsd-checking-for-ram-memory-size/ http://www.cyberciti.biz/faq/openbsd-checking-for-ram-memory-size/#comments Sun, 05 Jul 2009 12:30:38 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=8135 ]]> http://www.cyberciti.biz/faq/openbsd-checking-for-ram-memory-size/feed/ 0 UNIX / Linux: Send E-mail When sudo Runshttp://www.cyberciti.biz/faq/sudo-send-e-mail-sudo-log-file/ http://www.cyberciti.biz/faq/sudo-send-e-mail-sudo-log-file/#comments Wed, 01 Jul 2009 07:17:05 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=4281 I'm not told to use the root user to perform activities that do not require it. I've configured sudo for myself and for other web developers so that they can restart MySQL or Apache web server. How do I send email when sudo run by one of my user? How do I keep track of user login done via sudo command? ]]> http://www.cyberciti.biz/faq/sudo-send-e-mail-sudo-log-file/feed/ 10