7
votes
5answers
4k views

Is it worth the effort to block failed login attempts

Is it worthwhile running fail2ban, sshdfilter or similar tools, which blacklist IP addresses which attempt and fail to login? I've seen it argued that this is security theatre on a "properly ...
25
votes
5answers
9k views

CNAME for top of domain?

Is it possible to set a CNAME record at the top of a domain? (i.e. @ CNAME www, @ CNAME foobar.com., etc.) My ISP says that it's only possible to use CNAME's for subdomains but I've read somewhere ...
10
votes
2answers
2k views

Enabling hardware virtualisation BIOS; anything to beware?

A lot of recent virtualisation tools can either make use of, or demand, BIOS support (Intel-VT, AMD-V, etc). But in most of the BIOS screens I've seen, it has been disabled by default - sometimes even ...
7
votes
9answers
7k views

No free disk space [duplicate]

I have weird situation because Linux df command says that there is no free disk space [root@backup cache]# df -h Filesystem Size Used Avail Use% Mounted on /dev/sda3 72G ...
4
votes
5answers
5k views

How can I automaticaly change the DNS A record to point my site to a secondary server in case of a failure?

My hosting is charging me a $50/month fee to put my servers on the same VLAN so that I create a cluster using the Network Load Balancing feature. I'm really not needing split the load between the ...
3
votes
4answers
5k views

HP D2700 enclosure and SSDs. Will any SSD work?

I've got an HP D2700 enclosure that I'm looking to shove some 2.5" SSD drives in. Looking at the prices of HP's SSD drives vs something like an Intel 710 and even something less 'enterprisey', there's ...
7
votes
2answers
639 views

Difference between SSL products

I'm looking into getting a few SSL certificates for domains to cover the following: autodiscover.example.com remote.example.com www.example.com Wildcard certificates are too expensive, so I'm ...
1
vote
2answers
2k views

My OpenSolaris Server hangs when writing large files after upgrading zpool

yesterday I added new harddrives(four as a raidz1 and one as hot-spare) to a opensolaris server, after extending the zpool the server hangs when writing large files but not when reading large ...
25
votes
0answers
1k views

What should I name my Active Directory? [duplicate]

Possible Duplicate: Windows AD Domain naming recommendations There are a lot of really screwed up configurations out there, because people didn't take a minute to sit down and think about ...
4
votes
2answers
2k views

3rd party SSD drive in HP Proliant server only shows 3G transfer speed

After receiving some excellent advice in a previous question, we've bought a OWC Mercury Extreme Pro drive for use in our HP Proliant DL360 G7 server. Both the drive, and the P410i array controller, ...
3
votes
4answers
712 views

ssh delay when connecting

When connecting to one specific server (running Debian Lenny) it always takes about 5 seconds before it prompts me to enter a password. After login there is no noticable delay anymore. There is also ...
71
votes
6answers
137k views

Boot and Install Windows from a USB thumb drive

Installing Windows from a thumb drive is vastly superior to burning a copy to a DVD which will fill some landfill somewhere with toxic stuff. Not to mention it's about 50x faster to install Windows ...
59
votes
5answers
16k views

Active Directory explained

If you had to explain Active Directory to someone how would you explain it?
58
votes
3answers
20k views

How does IPv6 subnetting work and how does it differ from IPv4 subnetting?

This is a Canonical Question about IPv6 Subnetting. Related: How does IPv4 Subnetting Work? I know a lot about IPv4 Subnetting, and as I prepare to (deploy|work on) an IPv6 ...
36
votes
20answers
18k views

Storing a million images in the filesystem

I have a project that will generate a huge number of images. Around 1,000,000 for start. They are not large images so I will store them all on one machine at start. How do you recommended on ...
58
votes
11answers
16k views

Multiple data centers and HTTP traffic: DNS Round Robin is the ONLY way to assure instant fail-over?

Multiple A records pointing to the same domain seem to be used almost exclusively to implement DNS Round Robin as a cheap load balancing technique. The usual warning against DNS RR is that it is not ...
67
votes
7answers
54k views

Can anyone explain precisely what IOWait is?

As much as I have read about iowait, it is still mystery to me. I know it's the time spent by the CPU waiting for a IO operations to complete, but what kind of IO operations precisely? What I am also ...
55
votes
11answers
118k views

How do I find if there is a rogue DHCP server on my Network?

What's the best approach towards determining if I have a rogue DHCP server inside my network? I'm wondering how most admins approach these kinds of problems. I found "DHCP Probe" ...
123
votes
12answers
11k views

Should servers be turned off at night?

There is a server that is used from 4:30 am in the morning until ~ 22:00. Should it be turned off? I think that it is a server and that it won't have a problem to stay on, but serious professors are ...
95
votes
4answers
15k views

Should I quit using Ifconfig?

With the servers that mount Infiniband cards, when I use the ifconfig command, I get this warning: Ifconfig uses the ioctl access method to get the full address information, which limits hardware ...
36
votes
16answers
33k views

Is Round-Robin DNS “good enough” for load balancing static content?

We have a set of shared, static content that we serve up between our websites at http://sstatic.net. Unfortunately, this content is not currently load balanced at all -- it's served from a single ...
54
votes
6answers
12k views

Heartbleed: are services other than HTTPS affected?

The OpenSSL 'heartbleed' vulnerability (CVE-2014-0160) affects webservers serving HTTPS. Other services also use OpenSSL. Are these services also vulnerable to heartbleed-like data leakage? I'm ...
27
votes
5answers
38k views

What is the difference between SAN, NAS and DAS?

What is the difference between SAN, NAS and DAS?
17
votes
6answers
11k views

MySQL InnoDB - innodb_file_per_table cons?

By default MySQL InnoDB stores all tables of all DBs in one global file. You can change this by setting innodb_file_per_table in the config, which then creates one data file for each table. I am ...
31
votes
1answer
7k views

Why are my XFS filesystems suddenly consuming more space and full of sparse files?

I've run XFS filesystems as data/growth partitions for nearly 10 years across various Linux servers. I've noticed a strange phenomenon with recent CentOS/RHEL servers running version 6.2+. Stable ...
16
votes
7answers
20k views

Force local IP traffic to an external interface

I have a machine with several interfaces that I can configure as I want, for instance: eth1: 192.168.1.1 eth2: 192.168.2.2 I would like to forward all the traffic sent to one of these local ...
16
votes
5answers
22k views

how i can identify which process is making UDP traffic on linux?

my machine is continously making udp dns traffic request. what i need to know is the PID of the process generating this traffic. The normal way in TCP connection is to use netstat/lsof and get the ...
29
votes
6answers
10k views

Meaning of directories on Unix and Unix like systems

I've been using Linux for a couple of years now but I still haven't figured out what the origin or meaning of some the directory names are on Unix and Unix like systems. E.g. what does etc stand for ...
7
votes
3answers
26k views

iptables - Target to route packet to specific interface?

My home server has two main interfaces, eth1 (a standard internet connection) and tun0 (an OpenVPN tunnel). I'd like to use iptables to force all packets generated by a local process owned by UID ...
27
votes
6answers
37k views

Apache Default/Catch-All Virtual Host?

If I have 3 domains, domain1.com, domain2.com, and domain3.com, is it possible to set up a default virtual host to domains not listed? For example, if I would have: <VirtualHost 192.168.1.2 ...
22
votes
6answers
20k views

Why would a server not send a SYN/ACK packet in response to a SYN packet

Lately, we've become aware of a TCP connection issue that is mostly limited to mac and Linux users who browse our websites. From the user perspective, it presents itself as a really long connection ...
26
votes
13answers
3k views

Server Hosting from your House - $200 to $300 per month range

I'm a developer lacking some infrastructure knowledge. What is the fattest pipe I can get to my house in the $200 to $300 range? I'd like to host a few servers at my house. Then if my company gets ...
20
votes
5answers
5k views

Unix Server Partitioning & Filesystem Layout

There's a lot of contradictory information about Unix server partitioning out on the internet, so I need some advice on how to proceed. So far, on the servers I in our test environment I didn't ...
48
votes
6answers
37k views

Is X.Y.Z.0 a valid IP address?

Are IP addresses with a 0 in the last octet valid? 10.6.43.0 In my case, I have the the following netmask 255.255.252.0 What about a 0 for the other octets?
16
votes
4answers
7k views

Common wisdom about Active Directory authentication for Linux Servers?

What is the common wisdom in 2014 about Active Directory authentication/integration for Linux servers and modern Windows Server operating systems (CentOS/RHEL-focused)? Over the years since my first ...
14
votes
5answers
65k views

Huge amount of TIME_WAIT connections says netstat

Okay, this is creeping me out - I see about 1500-2500 of these: root@wherever:# netstat Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 ...
27
votes
8answers
25k views

Private IP address in public DNS

We have an SMTP only mail server behind a firewall which will have a public A record of mail.. The only way to access this mail server is from another server behind the same firewall. We do not run ...
24
votes
8answers
26k views

Will disabling hyperthreading improve performance on our SQL Server install

Related to: Current wisdom on SQL Server and Hyperthreading Recently we upgraded our Windows 2008 R2 database server from an X5470 to a X5560. The theory is both CPUs have very similar performance, ...
15
votes
10answers
28k views

How do I know if I am running 32 or 64-bit Linux?

what would be a command to run in different distros?
19
votes
12answers
49k views

How do I know if I'm working on a Virtual Machine or not?

Is there a way to know if the Windows machine I'm working on is virtual or physical? (I'm connecting with RDP to the machine. If it's a virtual machine it is working and handled by VMWare).
9
votes
9answers
23k views

How to repair/restore ubuntu 10.04 after 'sudo chmod / 777'

See Also: Why is “chmod -R 777 /” destructive? I changed file permissions recursively on the root directory / by executing sudo chmod -R / 777, and after that my system won't ...
10
votes
2answers
6k views

SSL site not using the correct IP in Apache and Ubuntu

I'm trying to set up an apache-ubuntu-php webserver. My webserver will host multiple SSL sites, each SSL site will have it's own IP address (unless there's a better way to do this). So I suppose the ...
13
votes
5answers
5k views

ZFS best practices with hardware RAID

If one happens to have some server-grade hardware at ones disposal, is it ever advisable to run ZFS on top of a hardware-based RAID1 or some such? Should one turn off the hardware-based RAID, and run ...
6
votes
4answers
2k views

Rotate logs of a dumb non-interactive application

Ubuntu 10.4 Server. I have a dumb non-interactive legacy service which is running constantly on my server. It is writing its log to a file with fixed name (/var/log/something.log). It does not ...
4
votes
3answers
5k views

How to diagnose causes of oom-killer killing processes

I have a small virtual private server running CentOS and www/mail/db, which has recently had a couple of incidents where the web server and ssh became unresponsive. Looking at the logs, I saw that ...
2
votes
1answer
1k views

Setting up a Rails 2.3.x app on EC2 for easy scalability

I'm running a simple rails stack on a single dedicated machine. We're reaching our full capacity and have absolutely no setup for scaling, just one app on one machine. I did some research and came up ...
26
votes
9answers
28k views

Disk full, du tells different. How to further investigate?

I have a SCSI disk in a server (hardware Raid 1), 32G, ext3 filesytem. df tells me that the disk is 100% full. If I delete 1G this is correctly shown. However, if I run a du -h -x / then du tells me ...
13
votes
9answers
32k views

NRPE unable to read output, but why?

I have this problem with NRPE, all the stuff I've found so far on the net seems to point me at things I've already tried. # /usr/local/nagios/plugins/check_nrpe -H nrpeclient gives NRPE v2.12 as ...
5
votes
6answers
26k views

Windows Event Log - email notification

Is there an easy way to send an email when a particular severity of event from a particular service hits the Windows server event log? This is on Windows Server 2003, if it makes a difference. n.b. ...
5
votes
4answers
19k views

Disabling RAID feature on HP Smart Array P400

I'm planning to use ZFS on my system (HP ML370 G5, Smart Array P400, 8 SAS disk). I want ZFS to manage all disks individually, so it can utilize better scheduling (i.e. I want to use software RAID ...

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