Category: GNU-Linux

24.05.2017

what is umask? umask defines what what access rights newly created files „are born“. we are all supposed to be created equal – but depending if you are a son of Rothchild, Rockefeller or born in Namibia – your previleges […]

24.05.2017

What is yum? yum is the default package manager for RPM-based linux distributions (CentOS, Fedora, RHEL, Oracle). It’s written in python and it stands for “Yellowdog Updater, Modified”, as it was originally called “yup”, the package manager for Yellow Dog […]

24.05.2017

What is glibc? The GNU C Library project provides the core libraries for the GNU system and GNU/Linux systems, as well as many other systems that use Linux as the kernel. These libraries provide critical APIs including ISO C11, POSIX.1-2008, […]

linux verbose output during boot – show more output kernel messages
24.05.2017

1. open up grub config file and remove vim /etc/default/grub; 2. on this line remove the word „quiet“ GRUB_CMDLINE_LINUX_DEFAULT=“resume=/dev/sda1 showopts splash quiet“ 3. re generate grub config files 3.1. on redhat/centos/suse12 grub2-mkconfig -o /boot/grub2/grub.cfg 3.1. on debian/ubuntu update-grub update-grub2 #which […]

22.05.2017

vim stresscpu.sh; # create new script file #!/bin/bash while true; do echo -n "+."; done; save and quit chmod u+x stresscpu.sh; # mark it runnable nohup stresscpu.sh & # run in background htop # streeeeeeessss! it is also a harddisk-stress […]

19.05.2017

What are kernel modules? What exactly is a kernel module? Modules are pieces of code that can be loaded and unloaded into the kernel upon demand without rebooting the system. Without modules, we would have to build monolithic kernels and […]

19.05.2017

these commands are equally valid, both commands add „content“ to the end of file – if file does not exists it will be created. echo "content" >> file; >>file echo "content"; echo $?; # returns the error level (1 = […]

19.05.2017

yeah i know i sometimes make fun of distributions that have like a partition for every /root/folder but well yes it has it’s reasons. suse12 uname -a; # tested with Linux suse 4.4.21-69-default #1 SMP Tue Oct 25 10:58:20 UTC […]

19.05.2017

there are plenty 😀 debian8.8 uname -a; # tested with Linux debian 3.16.0-4-686-pae #1 SMP Debian 3.16.43-2 (2017-04-30) i686 GNU/Linux find / -type d -iname bin /bin /usr/local/bin /usr/bin /usr/share/doc/libintl-perl/examples/simplecal/bin /usr/lib/klibc/bin suse12 uname -a; # tested with Linux suse 4.4.21-69-default […]

19.05.2017

little experiment shows in what order the config files are loaded after login… login as non-root user uname -a; # tested with Linux debian 3.16.0-4-686-pae #1 SMP Debian 3.16.43-2 (2017-04-30) i686 GNU/Linux Broadcast message from user@debian (pts/0) (Fri May 19 […]

16.05.2017

this article might be largely incomplete… kernel ringbuffer boot messages messages from the kernel during first stages of boot. # all distros dmesg; # show kernel ring buffer boot messages log # Centos7 only (debian8 has the file but it […]

16.05.2017

CentOS7 yum install psmisc # install pstree [root@centos user]# pstree systemd─┬─NetworkManager─┬─dhclient         │                └─2*[{NetworkManager}]         ├─agetty         ├─auditd───{auditd}         ├─chronyd   […]

15.05.2017

the commands used for xfs are different. this is only valid for ext3/ext4. preparation: you should move your /home to a separate partition. Warning! You will need to have „physical“ access to the server’s console in order to perform these […]

14.05.2017

ps -eo size,pid,user,command –sort -size | awk ‚{ hr=$1/1024 ; printf("%13.2f Mb ",hr) } { for ( x=4 ; x<=NF ; x++ ) { printf("%s ",$x) } print "" }’| head -10    1243.09 Mb /usr/sbin/mysqld –basedir=/usr –datadir=/var/lib/mysql –plugin-dir=/usr/lib/mysql/plugin –user=mysql […]

11.05.2017

one sunny day on Debian8.7 as a result of this action: dwaves.de/2017/05/10/linux-sftp-ssh-how-to-limit-users-to-their-home-directories/ i got the stated error message: /usr/bin/xauth:  timeout in locking authority file /home/user/.Xauthority root@debian:/home/user# ls -lah|grep ICE -rwxrwxrwx  1 user user 4.7K May 10 16:25 .ICEauthority # chmod […]

09.05.2017

very basic self made benchmarking http://dwaves.de/2014/12/10/get-info-about-hardware-and-bench-benchmark-it-with-linux/ http://dwaves.de/2015/02/19/linux-bash-md5-sum-benchmark/ Open Source Benchmark Suite – http://www.phoronix-test-suite.com/ Open Source Benchmark Results – http://openbenchmarking.org/ (Web) Server Benchmark http://blog.serverbear.com/ – (Web) Server Benchmark. example result hetzner VPS: http://dwaves.de/2014/09/30/benchmark-q7-virtual-quemu-server-from-hetzner-de-for-7-90e-per-month/ non-free: https://www.spec.org/ – The Standard Performance Evaluation Corporation […]