Jun 30, 2013
tom

Why should you run cd . before doing anything?

In this compilation of sysadmin horrors, one of the authors writes, as a rule of thumb: Always do a cd . before doing anything. Why would you want to do that? Asked by qdii You don’t. At least not just like that. The preceeding line in the quoted document is of importance: -Set up your prompt to do a `pwd` everytime you cd. -Always do a `cd .` before doing anything. This way, you as […]

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Jun 28, 2013
tom

What is the difference between /sbin/nologin and /bin/false?

I have often heard it recommended that a user account should be disabled by setting its shell to /bin/false. But, on my existing Linux systems, I see that a great number of existing accounts (all of them service accounts) have a shell of /sbin/nologin instead. I see from the man page that /sbin/nologin prints a message to the user saying the account is disabled, and then exits. Presumably /bin/false would not print anything. I also […]

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Jun 25, 2013
tom

Linux: How to know which process(s) are accessing my files?

I have a mounted partition, which I tried umounting and it’s giving me an error. There is a chance that some process is accessing some files in that mounted partition. How do I know, which process is accessing it, and which files? Or better, another way to ask this question: How to know all the processes that are accessing a resource? Such as a file? Asked by kingsmasher1 Run lsof /partitionname where “partitionname” is the […]

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Jun 24, 2013
tom

DNS wildcard entry from *.domain.com to www.domain.com

If a user enters ww2.domain.com he should be redirected to www.domain.com. This should be possible for all sort of subdomains (e.g. xxx.domain.com, ww.domain.com, …). How should I set up the DNS record? Will this DNS entry work? *.domain.com. CNAME (Type) 3600 (TTL) www.domain.com. Solution: There were several steps involved for this. First I created DNS wildcard entries like this *.domain.com A 3600 1.2.3.4 domain.com A 3600 1.2.3.4 Than in the webhost settings I added a […]

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Jun 22, 2013
tom

How to simulate air flow in a datacenter? [closed]

I have an idea for a datacenter architecture which, I believe, would be very effective in terms of passive cooling. I need to do air flow simulations to be sure that the idea is as great as I believe, before suggesting it to companies who design datacenters. I’ve read about several air flow simulations, but it seems that those software products require years of training, and moreover are adapted specifically to the specific industries which […]

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Jun 22, 2013
tom

Could this command wipe any data?

I know this is not the best question, but I’ve ran this command today and our server’s /home folder is now empty. Command: mysqldump –add-drop-table -u DB_USER -p DB_NAME > /home/mybackup.sql Asked by ProDraz If you entered this command exactly as you wrote it and if no one has replaced the mysqldump in your path with a compromised version, it will not delete anything, with the possible exception that it will overwrite any preexisting file […]

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Jun 21, 2013
tom

What is this in my syslog and should I be concerned?

I’m seeing a lot of the following line in /var/log/syslog: Jun 21 14:36:15 my-server kernel: [416219.080061] iptables denied: IN=eth0 OUT= MAC=ff:ff:ff:ff:ff:ff:the-mac-address:08:00 SRC=0.0.0.0 DST=255.255.255.255 LEN=328 TOS=0×00 PREC=0×00 TTL=128 ID=10081 PROTO=UDP SPT=68 DPT=67 LEN=308 This seems to happen just about every minute. Is this just my server trying to broadcast something and my own iptables denying it from happening? If so, what kind of service might do such a thing, and should I allow it? I’m running […]

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Jun 19, 2013
tom

Windows File Permissions and Attributes

I’m somewhat confused about the whole Windows file security scheme. I come from a unix background, so I don’t fully understand the relationship between file permissions/security settings and the attributes; specifically read-only, that a file can have. For example, if I log in as an administrator into my box and I have a file that allows full control for administrators, but has the read-only attribute set, that means I cannot write to that file? Is […]

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Jun 17, 2013
tom

What is the easiest way to upgrade my existing Perl 5.14 to Perl 5.16 on FreeBSD 9 using the ports system?

I use the ports system on FreeBSD. What is the easiest way to upgrade Perl using ports? I currently uninstall all of perl and it’s dependencies. I’d think there would be a cool way to upgrade Perl and all it’s dependencies. What would that be? Asked by EhevuTov see /usr/ports/UPDATING the entry from 20120630 has detailed description how to do it with portmaster or portupgrade Answered by arved Check more discussion of this question. Bookmark […]

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Jun 16, 2013
tom

Know if mysql has done its job

I started a mysql dump from the terminal. I am on Linux. mysqldump -u foto_admin -p foto_fotografare > /home/foto/foto_sql_back.sql It asked me to add a password. I did it and the mysql dump started. Now the terminal is stuck on there. It does not show any process. It just where I left it on the password request. When I look into the FTP I see the sql file and I see refreshing the FTP that […]

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