How to force umount a NFS directory on Linux?

ByEric Ma

The NFS server is down. It is reported “Stale NFS file handle”. I tried ‘umount’ and ‘umount -f’. But neither succeeded. # umount /mnt/store umount.nfs: /mnt/store: Stale NFS file handle # umount -f /mnt/store umount.nfs: /mnt/store: Stale NFS file handle How to force umounting the NFS without rebooting the Linux server? I usually have to…

How to allow websites’ .htaccess files in Apache2?

ByEric Ma

How to allow websites to use .htaccess files in Apache2 web servers? The AllowOverride directive controls this: http://httpd.apache.org/docs/current/mod/core.html#allowoverride To allow AllowOverride in a directory, add the following rules to the /etc/httpd/conf/httpd.conf or similar configuration file for your apache installation: <Directory “/var/www/www.example.com”> Options FollowSymLinks # # AllowOverride controls what directives may be placed in .htaccess files….

How to host multiple websites on a Apache Linux web server?

ByEric Ma

I have a Linux web server with Apache (httpd). How to host multiple websites on Apache? To host websites www.example1.com and www.example2.com on a single node with Apache2 on a single IP, you can use VirtualHost as follows. Edit /etc/httpd/conf/httpd.conf and add the following lines: NameVirtualHost *:80 <VirtualHost *:80> DocumentRoot /var/www/example1.com ServerName www.example1.com # Other…

How to redirect anything written on a file to another file in linux?

ByEric Ma

Suppose we have two files, a.txt and b.txt . If we write anything in a.txt & b.txt, it should be redirected to c.txt. tee may help for this purpose. tee: duplicate standard input You may try a command like this: echo “hello” | tee -a a.txt >>b.txt Both a.txt and b.txt will contain the “hello”….

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git push error

ByWeiwei Jia

$ git push error: The requested URL returned error: 403 Forbidden while accessing https://github.com/HarryWei/hummer.git/info/refs fatal: HTTP request failed Replace (or add) url=ssh://git@github.com/HarryWei/hummer.git with url=https://git@github.com/HarryWei/hummer.git under “[remote “origin”]” section in ~/.gitconfig file. Reference:http://stackoverflow.com/questions/7438313/pushing-to-git-returning-error-code-403-fatal-http-request-failed

Skype crashes because it cannot read data from “C:Documents and SettingsAdministratorLocal SettingsTemp”

ByWeiwei Jia

On my laptop, I install windows xp because it is user-friendly for me. However, Skype cannot be open because “The system is not unavailable”. At last, I find the “Skype” directory under “C:Documents and SettingsAdministratorLocal SettingsTemp” cannot be accessed. “C:Documents and SettingsAdministratorLocal SettingsTemp” is like temporary directory for specific user under Linux OS. Actually, for…

How to Passwordless SSH to an OpenWrt Router?

ByEric Ma

The good ssh-copy-id method which works well on common Linux seems not working for OpenWrt router. How to Passwordless SSH to an OpenWrt Router? OpenWrt’s SSH server is Dropbear. It can accept normal RSA keys. But the authorized_keys location is not the same as the openssh “~/.ssh/authorized_keys”. The location for the authorized_keys is /etc/dropbear/authorized_keys What…

Windows 7 repetitively tried to update but failed every time I boot Windows 7

ByEric Ma

Windows 7 repetitively tried to update but failed every time I boot Windows 7. It will reboot automatically several times itself. How should I fix it? First, you need to identify which update causes the problem. You can find this in the Updates control panel tool as follows. After identifying the failed package (e.g. KB3033929…

How to configure systemd to boot Linux to console mode (runlevel 3)?

ByEric Ma

How to configure Linux (am using Fedora 21) managed by systemd to boot to console (init 3) mode? systemd has the concept of targets as a more flexible replacement for runlevels in sysvinit. Runlevel 3 is emulated by multi-user.target. runlevel3.target is a symbolic link to multi-user.target. You can switch to ‘runlevel 3’ by running #…

How to make Fedora Linux not clean some files in /tmp/?

ByEric Ma

On my Fedora 20, I find that the system automatically clean up file under /tmp/. This is convenient. However, it cause some problems for some programs. For example, HDFS puts its DataNode pid file under /tmp/ by default like hadoop-hadoop-datanode.pid. After it is cleaned up, the hadoop-daemon.sh script will consider there is no DataNode running….