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…
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”….
I need to add nomodeset to make my GPU card work on Linux. Latest Fedora and Ubuntu and their derives use grub2. How to add nomodeset permanently to grub2 on Fedora and Ubuntu? The parameters grub2 will use are stored in its grub.cfg file. The grub.cfg file is generated from grub’s default settings file /etc/default/grub….
Firefox has multiple profiles and I am aware of choosing them by invoking firefox with the -P option. But I find that after one firefox instance under one profile is running, even I choose another profile during starting with -P, the new instance is still running under the existing profile. How to run firefox with…
I have some text files which contain some long lines. Now I would like to break lines to at most 80 characters. How to wrap long lines in a text file on Linux? The fold command can wrap lines. fold – wrap each input line to fit in specified width For your purpose, fold -w…
How to enable SSH service on Fedora Linux? By default, it seems ssh is not enabled. Fedora may not have sshd service installed/enabled by default. You will need to install and configure it by yourself. The following instructions is for Fedora 22 as an example. First, install the sshd server by # dnf install openssh-server…
How to merge upstream into local fork repo with git? Merging an upstream repository into your fork: https://help.github.com/articles/merging-an-upstream-repository-into-your-fork/ Merging an upstream repository into your fork: https://help.github.com/articles/merging-an-upstream-repository-into-your-fork/
We have 2 static .a libraries and we would like to merge them into a single one for easier usage. How to merge 2 .a libraries to one .a library on Linux? With GNU ar, you can specify the single command-line option -M and control it with a script supplied via standard input, like the…
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…
The default display manager on my Fedora 22 is gdm. If I would like to change it to other display manager like KDM, LightDM or other, which is the portable and reliable method? You can use the “system-switch-displaymanager” tools to manage the display manager. This is possibly the most portable way. To install it: #…
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 #…
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….
Hi, I noticed that your site serves AdSense ads through BuySellAds and it is not in an iframe. By default, BuySellAds puts the backfill ads in an iframe. Puting AdSense ads in iframe is violation of the terms. How do you make BuySellAds not put AdSense ads in an iframe? Thanks! To inline the ads…
How to deactivate a LVM logical volume activated by #vgchange -aay on Linux You may need to make a LVM volume group inactive and thus unknown to the kernel. To deactivate a volume group, use the -a (–activate) argument of the vgchange command. To deactivates the volume group vg, use this command # vgchange -a…
I have a disk from another server installed on a new server. However, when I try to make a filesystem on it, mkfs reports # mkfs -t ext4 /dev/sdd1 mke2fs 1.42.8 (20-Jun-2013) /dev/sdd1 is apparently in use by the system; will not make a filesystem here! This is a new disk to the new server….
On Fedora, after inserting/plugging in an exteranl hard disk with LVM partitions on it, the partitions will appear under /dev like /dev/lvm-group/lvm-partition. However, on CentOS 6, the LVM volumes do not appear automatically. How to mount LVM partitions from an external hard disk on CentOS? What you need on CentOS is to activate the LVM…
The problem is like this: I would like to send a GET request using curl and the content has spaces, such as curl “http://example.com/send?msg=hello world” The space and the “world” will be left away if this command is executed directory on Linux. How to encode spaces in curl request URL? You can use the –date-urlencode…
I want to run screen on a remote host on which I do not have root/sudo privilege and screen is not installed. I can compile or copy the screen program that can run on the host. However, it reports: “Cannot make directory ‘/var/run/screen’: Permission denied” As screen is not installed on the host, the directory…
I use curl to send requests to remote servers like following command. curl http://example.com/send –date-urlencode “data=hello” However, it is blocked by the network proxy squid in some networks with message like (some info anonymized with “…”): ERROR The requested URL could not be retrieved POST /… HTTP/1.1 Proxy-Authorization: Basic … User-Agent: Mozilla/4.0 (compatible;) Host: ……
There are various lightning cables on the market. I ever purchased one but it does not work for iPhone 6… How to identify a certificated lightning cable that is good for iPhone 6? (I know the cables from Apple will definitely work. But it takes time to receive one from Apple or not always easy…