How to simulate pressing multiple keys together on Linux?

This post introduces a key presser on Linux with xvkb. But how to simulate pressing multiple keys together on Linux? That is, I would like to have multiple keys such as “A” “B” “C” “D” pressed together and being hold. How to simulate this on Linux with programs/commands? You can make use of xdotool (xdotool: […]

How to set the replication factor for one file when it is uploaded by `hdfs dfs -put` command line in HDFS?

When uploading a file by the hdfs dfs -put command line in HDFS, how to set a replication factor instead of the global one for that file? For example, HDFS’s global replication factor is 3. For some temporary files, I would like to save just one copy for faster uploading and saving disk space. The […]

How to iterate all files and directories under a directory in Python?

How to iterate all files and directories under a directory in Python? For example, I would like to iterate each file and directory under /mnt/data/ /mnt/data/ |– file.txt `– great That is: /mnt/data/files.txt /mnt/data/great You can use the os.walk to do this: root, dirs, files = os.walk(path).next() root will be the path.dirs will contain the […]

How to detect whether Linux runs in UEFI or BIOS mode inside the Linux?

How to detect whether Linux runs in UEFI or BIOS mode inside the Linux itself without needed to boot the the management console of the mother board? You can detect whether Linux runs in EFI mode by checking whether /sys/firmware/efi exist. In bash, you can test by [ -d /sys/firmware/efi/ ] This technique is used […]

How to allow websites’ .htaccess files in Apache2?

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 force umount a NFS directory on Linux?

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

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. […]

How to run screen on a Linux host reporting “Cannot make directory ‘/var/run/screen’: Permission denied”?

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 […]

How to make curl request pass the Squid proxy?

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: … […]