21
votes
3answers
8k views

Linux - real-world hardware RAID controller tuning (scsi and cciss)

Most of the Linux systems I manage feature hardware RAID controllers (mostly HP Smart Array). They're all running RHEL or CentOS. I'm looking for real-world tunables to help optimize performance for ...
31
votes
5answers
6k views

Are VMware ESXi 5 patches cumulative?

This seems basic, but I'm confused about the patching strategy involved with manually updating standalone VMware ESXi hosts. The VMware vSphere blog attempts to explain this, but the actual process is ...
7
votes
2answers
4k views

Installing a third party application package on CentOS 6.4 fails due to missing dependencies libcrypto.so.10 and libssl.so.10

This is a Canonical Question about OpenSSL binary compatibility issues between Red Hat Enterprise Linux (and its derivatives) 6.4 and 6.5. This issue applies to a wide variety of third party ...
16
votes
1answer
8k views

Hosting a ZFS server as a virtual guest

I'm still new to ZFS. I've been using Nexenta but I'm thinking of switching to OpenIndiana or Solaris 11 Express. Right now, I'm at a point of considering virtualizing the ZFS server as a guest within ...
15
votes
3answers
2k views

Can I bind a (large) block of addresses to an interface?

I know that the ip tool lets you bind multiple addresses to an interface (eg, http://www.linuxplanet.com/linuxplanet/tutorials/6553/1/). Right now, though, I'm trying to build something on top of ...
85
votes
12answers
12k views

What solutions exist to allow the use of revision control for server configuration files? [closed]

In an environment with multiple system administrators, I see a few advantages to adding the server config files into a revision control system. Most notable are the ability to track changes, who made ...
117
votes
6answers
12k views

Are SSD drives as reliable as mechanical drives (2013)?

SSD drives have been around for several years now. But the issue of reliability still comes up. I guess this is a follow up from this question posted 4 years ago, and last updated in 2011. It's now ...
26
votes
2answers
80k views

Can I have multiple DHCP servers on one network?

This is a Canonical Question about Redundant DHCP Servers. Is it possible to have more than one DHCP server on the same LAN? What are the implications of doing this? What happens if there is ...
20
votes
4answers
4k views

Best Practices for preventing you from looking like a spammer [duplicate]

I'd like to feel more confident setting up mail for my clients with regards to false positives. Here's what I know: SPF records are good, but not every spam filter service/software (SFSS) uses ...
15
votes
6answers
15k views

Cygwin SSHd Autoblock Failed Logins

I'm running Cygwin with an SSH deamon on a Windows Server 2008 machine. I was looking at the Event Viewer and noticed as much as 5 to 6 failed login attempts per second (brute force) for the last week ...
7
votes
13answers
24k views

HP Proliant DL380 G4 - Can this server still perform in 2011?

Can the HP Proliant DL380 G4 series server still perform at high a quality in the 2011 IT world? This may sound like a weird question but we are a very small company whose primary business is NOT IT ...
2
votes
3answers
7k views

FTP and Apache permission issues

Im having issues as to which user should own my www directory - ftp or apache? When set to the ftp user, the user can add, remoe and easily modify files but php file system actions generate permission ...
33
votes
3answers
34k views

How can I connect to a Windows server using a Command Line Interface? (CLI)

Especially with the option to install Server Core in Server 2008 and above, connecting to Windows servers over a CLI is increasingly useful ability, if not one that's very widespread amongst Windows ...
53
votes
20answers
21k views

Should we host our own nameservers?

I currently have my ISP providing DNS for my domain, but they impose limitations on adding records. Therefore, I am thinking about running my own DNS. Do you prefer to host your own DNS, or is it ...
38
votes
15answers
3k views

What's your favorite ticketing system? [closed]

I'm in the market for a ticketing system and I'm curious what everyone else is using. I'd like to welcome everyone to post their favorite ticketing system and the reason they like it so much. My ...
49
votes
2answers
33k views

How do VLANs work?

What are VLANs? What problems do they solve? I'm helping a friend learn basic networking, as he's just become the sole sysadmin at a small company. I've been pointing him at various questions/answers ...
19
votes
4answers
22k views

How do I tell if my Windows server is swapping?

I'm using Process Explorer to monitor my windows server while it reconstructs some data. It's primarily a CPU intensive process, but I want to make sure it's not swapping. How can I tell if it is ...
20
votes
23answers
33k views

Finding the Public IP address in a shell script

I can find my IP address using ifconfig or hostname -i command. But how do I find my Public IP? (I have a static public IP but I want to find it out using unix command)
15
votes
6answers
6k views

Avoid linux out-of-memory application teardown

I'm finding that on occasion my Linux box runs out of memory and it starts tearing down random processes to deal with it. I'm curious what administrators do to avoid this? Is the only real ...
9
votes
2answers
3k views

Sharing Domain name between domain controller and webserver

In our network the name of the network domain is also the domain of the organisation's website (say, example.com). Externally people can enter example.com to visit our website but internally this ...
168
votes
11answers
53k views

Can I nohup/screen an already-started process?

I'm doing some test-runs of long-running data migration scripts, over SSH. Let's say I start running a script around 4 PM; now, 6 PM rolls around, and I'm cursing myself for not doing this all in ...
56
votes
14answers
32k views

Top level domain for private networks?

On our office network we have an internal DNS and all the hostnames are whatever.lan. On my VMware VMs, on their host-only network I call them whatever.vm. We now have a private IP space network in ...
33
votes
7answers
19k views

What is “anycast” and how is it helpful?

I'd never heard of anycast until a few seconds ago when I read this SF post. The wikipedia entry on it is quite formal and doesn't really evoke a mental picture of how it would be used. Can someone ...
56
votes
13answers
24k views

Why is RAID not a backup?

When someone mentions RAID in a conversation about backups, invariably someone declares that "RAID is not a backup." Sure, for striping, that's true. But what's the difference between redundancy and ...
45
votes
3answers
2k views

Assessing equipment damage following a lightning strike - Should I have planned more?

One of my client's sites received a direct lightning hit last week (coincidentally on Friday the 13th!). I was remote to the site, but working with someone onsite, I discovered a strange pattern of ...
20
votes
5answers
15k views

How do I differentiate “fake RAID” from real RAID?

The Ubuntu wiki page on FakeRaid says the following: [A] number of hardware products ... claim to be IDE or SATA RAID controllers... Virtually none of these are true hardware RAID ...
18
votes
3answers
69k views

How to run VMWare ESX or ESXi in a virtual machine?

Can VMWare ESX or ESXi be installed and used inside a virtual machine? It can be installed inside VMWare Workstation or Server, but then it doesn't work; the main symptoms are: It runs REALLY ...
14
votes
17answers
9k views

Who is your favorite VPS Provider? [closed]

Who is your favorite virtual hosting provider? I'm looking for your thoughts on SliceHost, Dreamhost VPS, Linode, 1and1 VPS, etc and why you like the particular provider you named. Thanks!
7
votes
1answer
6k views

How exactly does a SAS SFF-8087 breakout cable work? + RAID/connection questions

Please let me know if my question does not makes any sense as I am not sure if I am interpreting it correctly from my thoughts due to my lack of technical knowledge on this. If I am using a ...
13
votes
3answers
12k views

What should the order of DNS servers be for an AD Domain Controller and Why?

This is a Canonical Question about Active Directory DNS Settings. Related: What is Active Directory and how does it work? Assuming an environment with multiple domain controllers ...
9
votes
2answers
7k views

Third-party SSD solutions in ProLiant Gen8 servers

I was wondering if anyone had any specific experience using Intel DC3700 SSDs (or similar) in the HP (DL380p) Gen8 servers? I'm upgrading a set of database servers that use direct-attached storage. ...
13
votes
3answers
6k views

What happens when the USB key or SD card I've installed VMware ESXi on fails?

An SD (SDHC) card installed in an HP ProLiant DL380p Gen8 server running VMware ESXi just failed :( I encountered some ominous looking messages on the vCenter console and in the HP ProLiant ILO event ...
3
votes
1answer
3k views

Openfiler iSCSI performance

Hoping someone can point me in the right direction with some iSCSI performance issues I'm having. I'm running Openfiler 2.99 on an older ProLiant DL360 G5. Dual Xeon processor, 6GB ECC RAM, Intel ...
3
votes
3answers
3k views

Permission denied in vhost document root

I'm having a problem setting up a vhost on Apache 2.4, using CentOS 6.3. This question seems to have been answered several times on this forum, but none of the solutions work for me. Basically, I ...
2
votes
4answers
4k views

How can I stop a currently active DDoS attack? [duplicate]

My VPS is under a DDoS attack. I cannot access RDP, and I cannot take it offline, or access it in any way at all. What can I do? They are not trying to bruteforce, just trying to stop access to the ...
113
votes
26answers
211k views

Using DD for disk cloning

There's been a number of questions regarding disk cloning tools and dd has been suggested at least once. I've already considered using dd myself, mainly because ease of use, and that it's readily ...
88
votes
2answers
31k views

How do I select which Apache MPM to use?

I'm a little confused between the different MPMs offered by Apache - 'worker', 'event', 'prefork', etc. What are the major differences between them, and how can I decide which one will be best for a ...
50
votes
9answers
14k views

Company Password Management [closed]

The topic of personal password management has been covered in great detail time after time. This question is aimed at the business or organization that needs to keep track of many unique passwords for ...
11
votes
3answers
11k views

How to configure postfix to pipe all incoming email to a script?

Using postfix, I'd like all incoming mail, to any address (including those that don't map to local users) to be piped to a script. I've tried configuring mailbox_command in /etc/postfix/main.cf: ...
21
votes
3answers
16k views

Linux - How can I see what's waiting for disk IO

I have a server that has a really high load. Nothing is jumping out at me in terms of CPU usage, and it's not swapping. I think it's cause some processes are waiting for disk IO, and I want to see ...
27
votes
5answers
8k views

Debugger for Iptables

I'm looking for an easy way to follow a packet through the iptables rules. This is not so much about logging, because I don't want to log all traffic (and I only want to have LOG targets for very few ...
66
votes
14answers
4k views

What's wrong with always being root?

I have a feeling this is a stupid question, but this is something I've wondered for awhile. I have a VPS and this is my first big linux venture. I am the only person who has access to it. My question ...
33
votes
5answers
3k views

Smoothest workflow to handle SSH host verification errors?

This is a simple issue that we all face and probably resolve manually without giving much thought. As servers change, are re-provisioned, or IP addresses reallocated, we receive the SSH host ...
18
votes
9answers
12k views

Multiple domains with SSL on same IP

I know that a dedicated IP is needed for setting up SSL. What happens if we add SSL for domains sharing an IP ? (Namevirtualhost)
13
votes
4answers
8k views

Set root domain record to be a CNAME

I need to create an NS record for a domain that is a CNAME, for the purpose of having two domains pointed at one IP, and not having to maintain the current IP address in two different places. The DNS ...
8
votes
1answer
4k views

In DNS can an IN NS point to a CNAME?

Is it allowed to have an NS record be a CNAME? E.g.: subdomain.example.com. IN NS ns1.example.com. ns1.example.com. CNAME foo.example.com. foo.example.com. IN A ...
1
vote
1answer
191 views

Lame DNS server

I'm trying to setup my BIND with a domain I own and I'm using dnssy.com and intodns.com to check if everything is ok, but I'm getting errors in both. The error says that my DNS server is "lame" ...
14
votes
4answers
3k views

How is Windows Server different from regular Windows?

I can run IIS on a normal installation, what is so different about windows server?
2
votes
2answers
3k views

Non-volatile cache RAID controllers: what kind of protection is there against NVCACHE failure?

The battery back-up (BBU) model: admin enables write-back cache with BBU writes are cached to the RAID controller's RAM (major performance benefit) the battery saves uncommitted and cached data in ...
272
votes
21answers
49k views

How do you search for backdoors from the previous IT person?

We all know it happens. A bitter old IT guy leaves a backdoor into the system and network in order to have fun with the new guys and show the company how bad things are without him. I've never ...

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