It is common that the root disk space is not enough when running a Virtual Machine in the cloud such as Amazon Web Service (AWS). The cloud storage usually provides tools or facilities to enlarge a virtual disk size. However, to make the Linux recognize and and use the enlarged disks without rebooting the OS, […]
SysTutorials
1207 posts in total.
Do big data stream processing in the stream way
Reading: Years in Big Data. Months with Apache Flink. 5 Early Observations With Stream Processing: https://data-artisans.com/blog/early-observations-apache-flink. The article suggest adopting the right solution, Flink, for big data processing. Flink is interesting and built for stream processing. The broader view and take away may be to solve problems using the right solution. We saw many painful […]
How to set up Insync to synchronize Google Drive and Google Docs files in Ubuntu 18.04 Linux
Google Drive is a nice cloud storage service. It provides a suite of nice online document spreadsheet and slide editors Google Docs, Google Sheets and Google Slides. The collaborative editing and full history tracking features of Google Docs are excellent. Google Drive gives 16GB free storage which is pretty much larger compared to other free […]
Thunderbird Addons to Make Thunderbird Easier to Use
Thunderbird is powerful and feature rich. But different users have different needs and it is not feasible to include all features into the base software, where a plugin system shines. Thunderbird, similar to Firefox from Mozilla, supports addons/plugins and has a large ecosystems. Here, we will introduce several addons to Thunderbird that make Thunderbird easier […]
Handling Sparse Files on Linux
Sparse files are common in Linux/Unix and are also supported by Windows (e.g. NTFS) and macOSes (e.g. HFS+). Sparse files uses storage efficiently when the files have a lot of holes (contiguous ranges of bytes having the value of zero) by storing only metadata for the holes instead of using real disk blocks. They are […]
How to Add a File Based Swap for Linux
We may want to add some swap space for a Linux box while only find that all disk space is partitioned and mounted. Some partition has large available free space. For such cases, we may not want to change the partition allocation. The solution may be to add a file based swap for Linux as […]
How to resize a virtual disk of KVM
I test it for qcow2 format. Other formats are TBA. qemu-img resize kvm1.qcow2 +20G cp kvm1.qcow2 kvm1-orig.qcow2 virt-resize –expand /dev/sda1 kvm1-orig.qcow2 kvm1.qcow2 Reference: https://fatmin.com/2016/12/20/how-to-resize-a-qcow2-image-and-filesystem-with-virt-resize/ I test it for qcow2 format. Other formats are TBA. qemu-img resize kvm1.qcow2 +20G cp kvm1.qcow2 kvm1-orig.qcow2 virt-resize –expand /dev/sda1 kvm1-orig.qcow2 kvm1.qcow2 Reference: https://fatmin.com/2016/12/20/how-to-resize-a-qcow2-image-and-filesystem-with-virt-resize/ Answered by harryxiyou.
How to not use concrete types in lambda function parameters in C++11?
C++11 requires that lambda function parameters be declared with concrete types. This is sometimes annoying. auto is really nice, especially when the type is complex like std::vector<std::string>::iterator is quite long to type. I know C++14 allows auto in lambda functions. But how to not use concrete types in lambda function parameters in C++11? In C++11, […]
How to operator[] access element in a const map in C++?
How to operator[] access element in a const map in C++? For example, the compiler will report error on this piece of code: #include <iostream> #include <string> #include <map> std::int64_t count(const std::map<std::string, std::int64_t>& map) { return map[“one”] + map[“two”]; } int main () { std::map<std::string, std::int64_t> map = { {“one”, 1}, {“two”, 2} }; std::cout […]
How to hide my private IP in Email header in Thunderbird?
It seems Thunderbird sends out my private/lan IP to the SMTP server. For example, in an Email sent out by Thunderbird, the header contains Received: from [192.168.1.2] (example.com [1.2.3.4]) by mail.example.com (Postfix) with ESMTPSA id 92CD297DEA; It is fine that the SMTP server records the public IP (1.2.3.4) as it is what it sees. But […]
How to make Vim indent C++11 lambdas correctly?
Vim seems not indent C++11 lambas very well. How to make Vim indent C++11 lambdas correctly? For this following program, Vim indents it as #include <iostream> #include <string> #include <vector> #include <algorithm> int main () { std::vector<std::string> strs({“one”, “two”}); std::vector<std::string> newstrs; std::transform(strs.begin(), strs.end(), std::back_inserter(newstrs), [](const std::string& s) -> std::string { if (s == “one”) { […]
How to enable Email address auto completion in Evolution?
Does Evolution support automatic email address filling/completing in the “To” or “CC” fields which is commonly seen in other Email clients such as Thunderbird. Is is possible and how to enable Email address auto completion in Evolution? Evolution supports the contact autocompletion. To enable it, do as follows in Evolution. In Evolution Preferences dialog, in […]
How to make Evolution not wrap lines in composed Emails?
Evolution seems wrap long lines automatically in “Plain Text” mode. How to make Evolution not wrap lines in composed Emails? Evolution does not have (so far) “Flowing Text” mode where “the text is soft broken at the composer edge, but those soft breaks aren’t translated to hard breaks when the mail is sent” ( Reference: […]
How to list start and end sectors of a partition by parted in Linux?
How to list start and end of a partition by the sectors in parted on Linux? The default behavior seems be listing the start and end by bytes in parted. # parted /dev/sdc print Model: Innostor IS888 ext. HDD (scsi) Disk /dev/sdc: 2000GB Sector size (logical/physical): 512B/512B Partition Table: gpt Disk Flags: Number Start End […]
How to apply the Email sort order to all folders in Evolution?
Evolution’s default Email sort order is not very convenient, at least to me. How to apply the settings of sort order for a folder to all folders in Evolution? Manually setting the email sort order for each dir is tedious. Evolution has a function to “apply the same view settings to all folder” so that […]
How to search history commands very effectively in bash shell command line?
How to search history commands very effectively in bash shell command line? Just enter CTRL+r The function of above is: (reverse-i-search)`’: It is very fast and efficient. Answered by harryxiyou.
Why I cannot login remote server with its root
# ssh root@192.168.122.96 root@192.168.122.96’s password: Permission denied, please try again. Do according to [1]. NOTE: on Ubuntu, remember to restart ssh service like this “sudo restart ssh”. [1] https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/v2v_guide/preparation_before_the_p2v_migration-enable_root_login_over_ssh Answered by harryxiyou.
How to check CPU working frequency in iOS on iPhone?
How to check CPU working frequency in iOS on iPhone, such as my iPhone 6? The Litum Info Lite free app (Litum Info full version app) can show you the info of CPU including its frequency. The CPU frequency: You can find the CPU info page from the menu: Answered by Eric Z Ma.
How to remove newline characters from a string in C++?
How to remove newline characters from a string in C++? For example, a string like line 1 line 3 line 4 should be converted to line 1line 3line 4 In short, use this code snippet: input.erase(std::remove(input.begin(), input.end(), ‘\n’), input.end()); std::remove() shifts all elements that are equal to the value n by moving the elements in […]
How to change the default target of `make`?
The default target of make is the first target. But can I change the default target in Makefile and how to change the default target of make? The default goal of make is the first target whose name does not start with ‘.’ if .DEFAULT_GOAL is not set. Ref: make manual. To set the default […]
