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Questions tagged [linux]

Linux is the generic term for a UNIX-like open source operating system based on the Linux kernel.

GNU/Linux is a UNIX-like Open Source operating system. Linus Torvalds originally wrote the Linux kernel with contributions from others on the MINIX usenet board. Since then, Linux had thousands of developers, both paid by companies and volunteers. The main system tools and libraries for GNU/Linux are sourced from the GNU Project, hence the nomenclature GNU/Linux (GNU Toolchain over Linux Kernel). The Linux kernel is licensed under the GPL v2 license.

There are many different Linux Distributions (sometimes shortened to distro), which consist of software applications packaged and provided with the Linux kernel, being Slackware the oldest active distro and Debian, Red Hat and CentOS among the most used on Internet servers¹.

The Linux kernel is commonly run on servers but is highly portable and is used in a variety of applications, from wireless routers and cell phones to clusters and super computers with thousands of nodes and processors.

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Does the "bs" option in "dd" really improve the speed?

Every now and then, I'm told that to increase the speed of a "dd" I should carefully choose a proper "block size". Even here, on ServerFault, someone else wrote that "...the optimum block size is hardware dependent..." (iain) or "...the perfect size…
Damiano Verzulli
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How to sort ps output by process start time?

Is there a way to sort ps output by process start time, so newest are either at the top or bottom ? On Linux ? On SysV5 ? On Mac ?
Dean Smith
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Curl: disable certificate verification

I am developing and I need to access https://localhost. I know the certificate will not match. I just want curl to ignore that. Currently it gives me the following error message: curl: (51) SSL peer certificate or SSH remote key was not OK Is it…
blueFast
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Testing UDP port connectivity

I am trying to test whether I can get to a particular port on a remote server (both of which I have access to) through UDP. Both servers are internet facing. I am using netcat to have a certain port listening. I then use nmap to check for that port…
Lock
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Why is TCP accept() performance so bad under Xen?

The rate at which my server can accept() new incoming TCP connections is really bad under Xen. The same test on bare metal hardware shows 3-5x speed ups. How come this is so bad under Xen? Can you tweak Xen to improve performance for new TCP…
cgbystrom
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Heartbleed: how to reliably and portably check the OpenSSL version?

I was looking at a reliable and portable way to check the OpenSSL version on GNU/Linux and other systems, so users can easily discover if they should upgrade their SSL because of the Heartbleed bug. I thought it would be easy, but I quickly ran into…
Martijn
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Is there a proper way to clear logs?

I was wondering if there was a proper way to clear logs in general? I'm new to Ubuntu and I'm trying to set up Postfix. The log in question is /var/log/mail.log. I was wondering if there was a correct way to clear it, rather than me going in it and…
mastofact
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create home directories after create users

I created some users with: $ useradd john and I forgot to specify the parameter -m to create the home directory and to have the skeleton files copied to each user. now I want to do that, and I don't want to recreate all users (there must be an…
cd1
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Temporarily ignore my `~/.ssh/known_hosts` file?

Is there a way to temporarily ignore my ~/.ssh/known_hostsfile? mbp:~ alexus$ ssh 10.52.11.171 @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ @ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! …
alexus
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How to get TX/RX bytes without ifconfig?

Since ifconfig is apparently being deprecated in major Linux distributions, I thought I'd learn something about the ip tool that's supposed to be used instead of ifconfig. And here I ran into a problem: when run on its own, ifconfig shows the…
justinas
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Reread partition table without rebooting?

Sometimes, when resizing or otherwise mucking about with partitions on a disk, cfdisk will say: Wrote partition table, but re-read table failed. Reboot to update table. (This also happens with other partitioning tools, so I'm thinking this is a…
Teddy
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Service start request repeated too quickly, refusing to start limit

I have a systemd service that displays the following error service start request repeated too quickly, refusing to start I understand that the service is configured to restart on failure and it is restarting again and again. But when exactly does…
Vikas Tiwari
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Best way to disable swap in Linux

I am running a custom compiled 3.18.9 kernel and I am wondering about the best way to disable swap on the system. I also use init if it makes a difference. Is it enough to comment or remove the swap line in /etc/fstab to prevent swap from…
user283167
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How to apply a filter to real time output of `tail -f `?

tail -f path The above will output modifications to the file instantly, but I want to apply a filter to the output, only show when there is a keyword xxx in it. How to approach this?
wamp
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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 is, what is wrong with just logging in as root as…
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