One of HDFS cluster’s hdfs dfsadmin -report reports: Under replicated blocks: 139016 Blocks with corrupt replicas: 9 Missing blocks: 0 The “Under replicated blocks” can be re-replicated automatically after some time. How to handle the missing blocks and blocks with corrupt replicas in HDFS? Understanding these blocks A block is “with corrupt replicas” in HDFS
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Author: Eric Ma
Eric is a systems guy. Eric is interested in building high-performance and scalable distributed systems and related technologies. The views or opinions expressed here are solely Eric's own and do not necessarily represent those of any third parties.How to make AdSense responsive ads show rectangle ads instead of horizontal ones?
Posted onI noticed that many sites with AdSense responsive ads show large rectangle ads (336px x 280px) or large rectangle text ads (full width x 280px). However, in my own website (640px width content area), it shows most of time horizontal ones. How to make AdSense responsive ads show rectangle ads instead of horizontal ones? At
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How to find a wireless network adapter’s speed in Linux?
Posted onHow to find a wireless adapter‘s speed in Linux? ethtool does not show the speed of the wireless adapters. For finding the configured speed of wireless adpaters in Linux, you can use the iwconfig tool. iwconfig: configure a wireless network interface For example, to find the speed of the wireless adapter wlp8s0: # iwconfig wlp8s0
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How to find a network adapter’s speed in Linux?
Posted onI have a Linux box and it is connected to a network through a network adapter, say gate. How to find what is the current speed (10Mbps, 100Mbps or 1000Mbps) of the adapter? You can find the network adapter speed by the ethtool command: ethtool: query or control network driver and hardware settings For example,
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How to disable SSH reverse DNS lookup on Linux?
Posted onHow to disable the reverse DNS lookup by the SSD server on Linux? To turn off reverse DNS lookups of the SSH daemon, log on the server and add UseDNS no to /etc/ssh/sshd_config. And remember to restart the sshd service by service sshd restart or systemctl restart sshd.service or other commands depending on your system.
Implementation of strstr in glibc
Posted onWhat is the implementation of strstr in glibc? Implementation of STRSTR in glibc (string/strstr.c): /* Return the first occurrence of NEEDLE in HAYSTACK. Return HAYSTACK if NEEDLE is empty, otherwise NULL if NEEDLE is not found in HAYSTACK. */ char * STRSTR (const char *haystack_start, const char *needle_start) { const char *haystack = haystack_start; const
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Max number of Emails allowed to Sent from Gmail SMTP per day
Posted onGmail’s SMTP is convenient. You “sender” needs not to be always your Gmail address (but the emails will include your Gmail address in the header “send by”). I am wondering how many emails at maximum can I send each day through Gmail’s SMTP. Here there a nice recent list of the sending limits of the
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How to exclude last N columns in Bash on Linux?
Posted onHow to exclude last N columns of a string in bash? The point is that the number of columns in each line is uncertain (but > N). For example, I would like to remove the last 2 columns separated by ‘.’ in the following lines. systemd.3.gz systemd.mount.3.gz systemd.mount.f.3.gz The simple cut command cut -d’.’ -f1
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Vim turns to be slow after enabling some plugins, how to find which leads the problem?
Posted onVim itself is very fast. But it turns to be slow after enabling some plugins. How to find which plugin leads the slowness of Vim? You may use the profiling mechanisms in Vim. Please check a tutorial on profiling Vim. For profiling Vim startup: vim –startuptime profile.log For profiling certain actions in Vim: :profile start
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List of all Xen hypervisor command line options
Posted onWhere can I find a list of all Xen hypervisor command line options that can be passed to Xen hypervisor during boot? This page lists all options of Xen hypervisor: Xen Hypervisor Command Line Options
Required packages for building YouCompleteMe for Vim on Fedora 21
Posted onYouCompleteMe for Vim on Fedora 21 reports this error: [zma@laptop:~/.vim/bundle/YouCompleteMe]$ ./install.sh — The C compiler identification is GNU 4.9.2 — The CXX compiler identification is GNU 4.9.2 — Check for working C compiler: /usr/bin/cc — Check for working C compiler: /usr/bin/cc — works — Detecting C compiler ABI info — Detecting C compiler ABI info
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How to edit eps file?
Posted onI have made some eps figures for my paper but now I wanna modify them. How to edit them now? You may try inkscape on Linux: https://inkscape.org/en/ It can edit eps files.
How to redirect WordPress search query to Google CSE?
Posted onHow to redirect WordPress search query to Google CSE? You can configure Google CSE to read the query variable (by default, it is q). Then, in your WordPress’s .htaccess file, add these 2 lines RewriteCond %{QUERY_STRING} ^s=(.*)$ RewriteRule ^ https://www.google.com/cse/publicurl?cx=xyz&q=%1 [R,L] Here, “https://www.google.com/cse/publicurl?cx=xyz” is your CSE’s public URL or the webpage that contains the Google
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How to move all the files under Users for a user to another drive on Windows?
Posted onUnfortunately, my C: drive is almost full. Most of the space are used by the user home under C:Users. How can I move the home directory to another drive while not affecting the user’s usage of Windows. On Linux/Unix, moving the directory to another drive/partition and then keeping a softlink is enough. But how to
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How to find which program or process is listening on a certain port in Linux?
Posted onMy program reports that the port is already used. How to find which program or process is listening on a certain port in Linux? You can use netstat to do this. netstat can print network connections. For example, to find which program is listing on port 9999 netstat -pln | grep 9999 You will need
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How to quite VirtualBox scale mode?
Posted onHow to quite VirtualBox scale mode? Use this hot key shortcut to quit VirtualBox scale mode Right_Ctrl + c
How to limit the network rate used by scp in Linux?
Posted onI am using a shared network and scp to upload files. I do not want to use most of the bandwidth available. How to limit the network rate used by scp in Linux? You can use the -l option of scp to limit the rate of bandwidth. -l limit Limits the used bandwidth, specified in
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VirtualBox report “Kernel driver not installed” on Fedora 21
Posted onVitualBox is installed on Fedora 21 by # yum install VirtualBox The following packages are installed kmod-VirtualBox-3.18.7-200.fc21.x86_64-4.3.20-4.fc21.4.x86_64 VirtualBox-4.3.20-3.fc21.x86_64 There is the kernel modules package installed. However, when running virtualbox (after reboot), it reports: [zma@laptop:~]$ virtualbox WARNING: The vboxdrv kernel module is not loaded. Either there is no module available for the current kernel (3.18.7-200.fc21.x86_64) or
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How to resolve a domain name from a specific DNS server instead of the configured one in Linux?
Posted onI would like to check whether the domain name’s IP has changed in the authoritative DNS server. The system’s configured DNS server may still cache the old IP, which is fine. The question is how to query from the authoritative DNS server the new IP? You can use dig – DNS lookup utility to query
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How to configure interface bonding in Linux?
Posted onHow to configure interface bonding to bound to 2 eth interfaces together in Linux, specifically CentOS/RHEL? This tutorial Configuring Interface Bonding on CentOS/RHEL/OEL 6.x introduces setting up interface bonding well on CentOS / RHEL / OEL 6.