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I found this interesting: amount of evil traffic on the internet
by Fred Smith 11 Jul '17

11 Jul '17

I've just done a little "study" (well, nothing quite that pretentious) of the traffic hitting my router, that gets DROPped the router's firewall. there is a surprisingly (to me, at least) enormous amount of it. over about the last 3 weeks, it has dropped over 65,000 connection attempts. I finally got around to figuring out how to have the router's logging mechanism connect to the rsyslog on my Centos workstation, so I can collect a large body of log entries to review. previously I could see only a few hundred at a time, since the router doesn't have huge storage. Here's just the first few items from the list, listed as port number ordered by total number of hits: DPT=3343 8859 DPT=23 7872 DPT=3344 5984 DPT=6 4925 DPT=68 4291 DPT=9 2625 DPT=3291 2524 DPT=32915 2523 DPT=143 2467 DPT=1433 2377 DPT=445 2037 DPT=33441 1544 DPT=33442 1522 DPT=33440 1511 DPT=33434 1511 DPT=33435 1487 DPT=33436 1486 DPT=33437 1476 DPT=33439 1458 DPT=33438 1439 DPT=80 1068 DPT=33443 1060 DPT=5060 948 Some of those are ports I've never been aware of, such as 3343, which /etc/services lists as "ms-cluster-net". Obviously something on MS systems, and apparently a lot of mal-dudes think it's a great port to hit on, in case it might just happen to be wide open. then there's port 23 (telnet) which at 7872 hits is ample evidence for why everybody who knows anything says to NEVER put a system on the internet with an open telnet port. sigh. Then, even after all this garbage is filtered out, there is another HUGE pile of things hitting my mail server that get filtered out by a variety of filtering techniques including but not limited to greylisting email. (BTW, greylisting was by far the most effective of all the filtering techniques I've found for dropping spam before it ever gets into my mail system. For mail that does get in, SpamBayes works great, once one figures out how to configure it.) If any of you don't believe that the 'net is populated by evil beings, let this be a lesson to ye! Thanks for your time! Fred -- ---- Fred Smith -- fredex(a)fcshome.stoneham.ma.us ----------------------------- "For the word of God is living and active. Sharper than any double-edged sword, it penetrates even to dividing soul and spirit, joints and marrow; it judges the thoughts and attitudes of the heart." ---------------------------- Hebrews 4:12 (niv) ------------------------------

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System Start-Up Issue
by Chris Olson 10 Jul '17

10 Jul '17

We run several Intel-based CentOS machines. They are all at 6.9 or 7.x. One of each OS is Oracle VirtualBox hosted on an up to date Windows 7 system. We use these virtual machines for checkout of new applications before they are loaded on native CentOS platforms. Regular weekly updates are run on all of our CentOS machines. I went on vacation right after an update to one of our virtual CentOS 6.9 systems so it was not restarted for a period of time. Now it will not complete boot-up with the gnome display never fully launched. A progress bar at the bottom of the start-up screen never reaches completion. We have not been able to detect a running system on the network. Two options for stopping the CentOS 6.9 virtual machine have been tried. One is to "power off" and the other is to "send the shutdown message". Both of these options appear to work properly. The shutdown output scrolls by very fast but it looks reasonable and the virtual machine eventually closes. We have also tried suspending boot-up and selecting two previous working kernels. This yields the same result of an incomplete start up. Shutdown of these old kernel systems appears the same as shutdown of the newest kernel. However, we have not been able to determine from any of the shutdown sequences exactly how much of the system was actually running. Having very little experience with such start-up issues, we are at a loss to determine how to salvage the CentOS 6.9 virtual machine. Is there a standard way to start up a system without any extras like gnome to see if we can get a running system? Would it be wise to attempt using yum update after we get a running system to see if issues are corrected? Thanks.

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Differences in CentOS and RHEL systems
by Kumuda G 10 Jul '17

10 Jul '17

Hi, I was looking at the differences between the CentOS and RHEL systems, found that tuned profile is different for these OSes. I have gone through RHEL 7 Performance Tuning Guide to see if there are more such changes, sysctl settings change which are due to tuned profile and did not find any other differences Also took diff of /etc/* config files on RHEL and CentOS installed systems, there are RHEL subscription and bugzilla references which vary So, are there more such system wide differences on CentOS? Regards, Kumuda G

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CentOS 7.3 and e1000e
by Jerry Geis 09 Jul '17

09 Jul '17

Hi All - I have a box running the above. Power was lost long enough that UPS did not work. When power came back on the C7 box boots way faster than the switch and resulted in no network. power cycling the C7 box resulted in network. This even happened a second time. The only way to get the box back was to power cycle. the box is remote and no keyboard and mouse connected. Any thoughts on why the e1000e would not talk to the switch ? The switch is an unmanaged linksys - could not get the model. It auto negotiates to 1G/full. Thanks, for any thoughts. Jerry

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Hardening Apache on CentOS 7
by Nicolas Kovacs 09 Jul '17

09 Jul '17

Hi, Some time ago one of my public servers (running Slackware64 14.0) got attacked and was misused to send phishing emails. This misadventure made me more concerned about security, so I spent the last few weeks catching up on security, reading docs about SELinux and how to use it, etc. I have a public sandbox server running CentOS 7, and I'm currently experimenting quite a lot with Apache and how to secure it. My approach is very much trial-and-error. I've started with these two articles: https://devops.profitbricks.com/tutorials/how-to-harden-the-apache-web-serv… https://www.tecmint.com/apache-security-tips/ I've also discovered the Nikto vulnerability scanner, and I'm playing around with it. Besides all this, I'd be curious to know your approach in securing Apache, the tools you use, maybe the odd do's and don'ts, suggestions, some good books and/or online docs about the subject, etc. Cheers from the sunny South of France, Niki -- Microlinux - Solutions informatiques durables 7, place de l'église - 30730 Montpezat Web : http://www.microlinux.fr Mail : info(a)microlinux.fr Tél. : 04 66 63 10 32

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performance problems with OpenLDAP and multiple simultaneous clients
by John Jasen 09 Jul '17

09 Jul '17

Running CentOS7, with openldap-2.4.40-13.el7. The environment consists of two ldap providers, in mirror mode, serving over a shared virtual IP. Client-facing services are provided by 4 consumers, most of which are accessed over a layer 4 load balancer. Periodically, the consumers encounter some sort of client request(s) which consume all available threads, cause backload threads to spike, and cause slapd to go unresponsive for a long period of time. I've no idea what is causing these events, or if there is anything in the configurations that I can tweak to help. Anyone have any ideas?

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Apache + mod_evasive : problem with test.pl
by Nicolas Kovacs 09 Jul '17

09 Jul '17

Hi, I'm currently experimenting with the mod_evasive module for Apache, to protect the server against potential DoS attacks. Here's what I did so far. # yum install mod_evasive Don't touch mod_evasive's default configuration, just restart Apache. # systemctl restart httpd The package includes a test.pl script supposed to launch a testing DoS attack. Unfortunately this script doesn't seem to work as expected. Here's the only response I get: # perl test.pl HTTP/1.1 400 Bad Request HTTP/1.1 400 Bad Request HTTP/1.1 400 Bad Request HTTP/1.1 400 Bad Request HTTP/1.1 400 Bad Request HTTP/1.1 400 Bad Request HTTP/1.1 400 Bad Request ... According to the various online tutorials I found, this should more look like: # perl test.pl HTTP/1.1 200 OK HTTP/1.1 200 OK HTTP/1.1 200 OK HTTP/1.1 200 OK HTTP/1.1 200 OK ... HTTP/1.1 403 Forbidden HTTP/1.1 403 Forbidden HTTP/1.1 403 Forbidden ... I tried this on two sandbox machine, one on my LAN, one on a public server, and both times I got the same result. Any suggestions? Niki -- Microlinux - Solutions informatiques durables 7, place de l'église - 30730 Montpezat Web : http://www.microlinux.fr Mail : info(a)microlinux.fr Tél. : 04 66 63 10 32

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Re: [CentOS] CentOS 7.3 and e1000e
by Richard Beels 09 Jul '17

09 Jul '17

At 07/07/2017 at 22:00, Shakespearean monkeys danced on Jerry Geis's keyboard and said: >Any thoughts on why the e1000e would not talk to the switch ? The switch is >an unmanaged linksys - could not get the model. It auto negotiates to >1G/full. +1 on the switch not being completely up itself. You could also stick in a (longer) pause at the boot screen. Cheers!

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certificate for www.xxxx.xx has expired ?? (hostname)
by Günther J. Niederwimmer 08 Jul '17

08 Jul '17

Hello, I found this Morning a Message in my Logs, that is new for me and I never seen this before? Is this a Error in the Certificate System?? The certificate for www.example.at has expired Datum: 08.07.17 06:31 Von: root <gjn+www(a)example.at> An: gjn+www(a)example.at ################# SSL Certificate Warning ################ Certificate for hostname 'www.example.at', in file (or by nickname): /etc/pki/tls/certs/localhost.crt The certificate needs to be renewed; this can be done using the 'genkey' program. Browsers will not be able to correctly connect to this web site using SSL until the certificate is renewed. ########################################################## Generated by certwatch(1) what is the best way to correct this Problem? -- mit freundlichen Grüssen / best regards, Günther J. Niederwimmer

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mdraid doesn't allow creation: device or resource busy
by adam_kalisz 07 Jul '17

07 Jul '17

Dear fellow CentOS users, I have never experienced this problem with hard disk management before and cannot explain it to myself on any rational basis. The setup: I have a workstation for testing, running latest CentOS 7.3 AMD64. I am evaluating oVirt and a storage-ha as part of my bachelors thesis. I have already been running a RAID1 (mdraid, lvm2) for the system and some oVirt 4.1 testing. Now I added 6x 500 GB platters from an old server running Debian 8 Jessie with software RAID of a similar fashion as well. That would unexpectably prevent the system from booting past something like (I copied it from the working setup), I ran it over night, so it was actually about 16 hours: "A start job is running for dev-mapper-vg0\x2droot.device (13s / 1min 30s)" Can it be just some kind of a scan, which takes so long? The current throughput based on time (16 h) and capacity (3 TB) would be about 50 MBps. (Those drives can be pretty slow when writing, dd showed about 30 MBps, the write cache is off.) This is actually repeatable. If I unplug those drives and boot again, it all works. I don't know, if it helps but before that I had two screens full of: "dracut-initqueue[331]: Warning: dracut-initqueue timeout - starting timeout scripts" Well, I proceded without this array, and after it booted I connected the array of 6 hard disks again. They were recognized etc. The problem is, I cannot do much. I can dd from and to the harddrives, I can create and delete partitions but I cannot create an md raid array out of them, I cannot create a physical volume or format them with a filesystem. I even tried overwriting all of those harddrives with zeroes, which worked but didn't help at all with the creation of the array afterwards. mdadm --create /dev/md6 --level=5 --raid-devices=6 /dev/sd[cdefgh]1 "mdadm: cannot open /dev/sdc1: Device or resource busy" with pvcreate, it seems as if there was no device, but I clearly see it in /dev/sdc1... "Device /dev/sdc1 not found (or ignored by filtering)." partprobe yields: "device-mapper: remove ioctl on ST3500630NS_9QG0P0PY1 failed: Device or resource busy Warning: parted was unable to re-read the partition table on /dev/mapper/ST3500630NS_9QG0P0PY (Device or resource busy). This means Linux won't know anything about the modifications you made. device-mapper: create ioctl on ST3500630NS_9QG0P0PY1part1-mpath- ST3500630NS_9QG0P0PY failed: Device or resource busy device-mapper: remove ioctl on ST3500630NS_9QG0P0PY1 failed: Device or resource busy" In some forums, it was suggested, dmraid (yes, the old) could be the trouble. I eliminated this hypothesis (overwritten all with zeroes, fakeraid was never present with these disks). Also multipathd/ dm_multipath could be the trouble, someone suggested. The problem is, if I was to remove device-mapper-multipath, I would loose oVirt-engine, because it has multipath as dependency for some reason. Do you have any ideas? What logs/ information should I provide if you want to have a look into this. Best regards Adam Kalisz

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