Frequently Asked Questions About Linux / UNIX » Linux http://www.cyberciti.biz/faq Every answer asks a more beautiful question. Fri, 03 Feb 2012 22:38:32 +0000 en hourly 1 http://wordpress.org/?v=3.3.1 HowTo: Flush Contents Of a Memcached Server Using Command Linehttp://www.cyberciti.biz/faq/linux-unix-flush-contents-of-memcached-instance/ http://www.cyberciti.biz/faq/linux-unix-flush-contents-of-memcached-instance/#comments Sat, 28 Jan 2012 00:35:21 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11475 I've installed memcached server under Linux but it is still showing old data. How do I flush the contents of a Memcached instance / server?]]> http://www.cyberciti.biz/faq/linux-unix-flush-contents-of-memcached-instance/feed/ 1 Debian Linux Install MySQL Database Serverhttp://www.cyberciti.biz/faq/howto-debian-mysql-install-apt-get-commands/ http://www.cyberciti.biz/faq/howto-debian-mysql-install-apt-get-commands/#comments Mon, 23 Jan 2012 22:14:44 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11427 How do I install mysql database server under Debian Linux operating system running on HP server?]]> http://www.cyberciti.biz/faq/howto-debian-mysql-install-apt-get-commands/feed/ 1 Linux / Unix: Sed Substitute Multiple Patterns [ Find & Replace ]http://www.cyberciti.biz/faq/howto-sed-substitute-find-replace-multiple-patterns/ http://www.cyberciti.biz/faq/howto-sed-substitute-find-replace-multiple-patterns/#comments Fri, 20 Jan 2012 10:58:16 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11420 I'm using the date +'%D_%T' to store Unix system date and time in a shell variable called $_now:
_now="$(date +'%D_%T')" echo $_now Outputs: 01/20/12_16:10:42
I'd like to replace / and : with _. I'm aware of the following sed command:
sed 's/\//_/g > s/:/_/g' <<<"$_now" Outputs: 01_20_12_16_14_09
How do I specify two pattern within the same sed command to replace | and : with _ so that I can get output as 01_20_12_16_10_42?]]> http://www.cyberciti.biz/faq/howto-sed-substitute-find-replace-multiple-patterns/feed/ 1 Reload Squid Proxy Server Without Restarting Squid Daemonhttp://www.cyberciti.biz/faq/howto-linux-unix-bsd-appleosx-reload-squid-conf-file/ http://www.cyberciti.biz/faq/howto-linux-unix-bsd-appleosx-reload-squid-conf-file/#comments Wed, 18 Jan 2012 11:45:43 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11401 I made some changes to the /etc/squid/squid.conf file and issued the command /sbin/service squid restart. However, this command takes way too much time to restart the server. How do I tell squid to just reread the config file and apply new changes under Linux operating systems?]]> http://www.cyberciti.biz/faq/howto-linux-unix-bsd-appleosx-reload-squid-conf-file/feed/ 2 Debian Linux Install OpenSSH SSHD Serverhttp://www.cyberciti.biz/faq/debian-linux-install-openssh-sshd-server/ http://www.cyberciti.biz/faq/debian-linux-install-openssh-sshd-server/#comments Wed, 11 Jan 2012 13:06:15 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11384 How do I install OpenSSH sshd server under Debian GNU/Linux operating systems?]]> http://www.cyberciti.biz/faq/debian-linux-install-openssh-sshd-server/feed/ 0 Linux / Unix: SysVinit Services Restart vs Reload vs Condrestarthttp://www.cyberciti.biz/faq/linux-unix-sysvinit-services-restart-vs-reload-vs-condrestart/ http://www.cyberciti.biz/faq/linux-unix-sysvinit-services-restart-vs-reload-vs-condrestart/#comments Thu, 05 Jan 2012 21:24:25 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11349 Can you tell me differences between the following sysvinit /sbin/service command:
service httpd restart service httpd condrestart service httpd reload
]]> http://www.cyberciti.biz/faq/linux-unix-sysvinit-services-restart-vs-reload-vs-condrestart/feed/ 0 Linux: Find Out Open Files [ Descriptors ] Commandhttp://www.cyberciti.biz/faq/linux-find-total-open-files-descriptors/ http://www.cyberciti.biz/faq/linux-find-total-open-files-descriptors/#comments Wed, 04 Jan 2012 18:25:02 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11334 How do I find out that how many files are open and how many allowed in Linux server operating systems?]]> http://www.cyberciti.biz/faq/linux-find-total-open-files-descriptors/feed/ 2 CentOS / RHEL: yum Command Reinstall Packagehttp://www.cyberciti.biz/faq/centos-redhat-fedora-linux-yum-reinstall-package-command/ http://www.cyberciti.biz/faq/centos-redhat-fedora-linux-yum-reinstall-package-command/#comments Fri, 30 Dec 2011 11:05:21 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11311 I accidental deleted the configuration file stored in /etc/ directory and the latest backup were made yesterday. How do I resinstall the package using the yum command under RHEL / CentOS Linux server?]]> http://www.cyberciti.biz/faq/centos-redhat-fedora-linux-yum-reinstall-package-command/feed/ 1 CentOS / RHEL: Change / Copy File SELinux Security Context Commandhttp://www.cyberciti.biz/faq/rhel-centos-feora-linux-change-copy-selinux-context/ http://www.cyberciti.biz/faq/rhel-centos-feora-linux-change-copy-selinux-context/#comments Wed, 28 Dec 2011 10:29:40 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11302 I've created a file as follows:
ls -l -Z /etc/cron.d/vnstat -rw-r--r--. root root system_u:object_r:system_cron_spool_t:s0 /etc/cron.d/vnstat
I've created a new file /etc/cron.d/vnstat.custom.interface:
ls -l -Z /etc/cron.d/vnstat.custom.interface -rw-r--r--. root root unconfined_u:object_r:system_cron_spool_t:s0 /etc/cron.d/vnstat.custom.interface
The /etc/cron.d/vnstat is part of default vnstat package. I've installed my own version of the same. But, due to SELinux security cron job is not running. How do I change file SELinux security contex under RHEL / CentOS 6 Linux server to system_u:object_r:system_cron_spool_t:s0 from unconfined_u:object_r:system_cron_spool_t:s0 for /etc/cron.d/vnstat.custom.interface file?]]> http://www.cyberciti.biz/faq/rhel-centos-feora-linux-change-copy-selinux-context/feed/ 0 Linux: Find Out What Partition a File Belongs Tohttp://www.cyberciti.biz/faq/linux-unix-command-findout-on-which-partition-file-directory-exits/ http://www.cyberciti.biz/faq/linux-unix-command-findout-on-which-partition-file-directory-exits/#comments Mon, 19 Dec 2011 20:18:00 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11270 How do I find out that /users/f/foo/file.txt file belongs to a specific partition?]]> http://www.cyberciti.biz/faq/linux-unix-command-findout-on-which-partition-file-directory-exits/feed/ 1 Linux / Unix curl: Pass HTTP Refererhttp://www.cyberciti.biz/faq/linux-unix-appleosx-bsd-curl-command-httpreferer/ http://www.cyberciti.biz/faq/linux-unix-appleosx-bsd-curl-command-httpreferer/#comments Sun, 06 Nov 2011 22:01:47 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11185 How do I pass the referrer (HTTP referrer)as an HTTP header field using curl command under Linux OR Unix operating systems?]]> http://www.cyberciti.biz/faq/linux-unix-appleosx-bsd-curl-command-httpreferer/feed/ 0 memcached: Failed To Set rlimit For Open Files Error and Solutionhttp://www.cyberciti.biz/faq/linux-unix-rhel-centos-memcache-failedto-setrlimit/ http://www.cyberciti.biz/faq/linux-unix-rhel-centos-memcache-failedto-setrlimit/#comments Tue, 11 Oct 2011 18:36:21 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11153 I'm using RHEL 6 / CentOS 6.x and install the memcached server. However, whey I try to start the server using service memcached start command, I get the following error:
Starting memcached: failed to set rlimit for open files. Try running as root or requesting smaller maxconns value. [FAILED]
How do I fix this problem?]]> http://www.cyberciti.biz/faq/linux-unix-rhel-centos-memcache-failedto-setrlimit/feed/ 2 Mplayer Shuffle Command: Play Files In Random Orderhttp://www.cyberciti.biz/faq/mplayer-shuffle-ubuntu-redhat-fedora-debian-bsd/ http://www.cyberciti.biz/faq/mplayer-shuffle-ubuntu-redhat-fedora-debian-bsd/#comments Sat, 01 Oct 2011 12:44:08 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11147 How do I play files in random order using the mplayer command line player under Linux / Unix operating systems?]]> http://www.cyberciti.biz/faq/mplayer-shuffle-ubuntu-redhat-fedora-debian-bsd/feed/ 7 Bash Shell: Find Out If a Variable Is Set or Nothttp://www.cyberciti.biz/faq/linux-unix-howto-check-if-bash-variable-defined-not/ http://www.cyberciti.biz/faq/linux-unix-howto-check-if-bash-variable-defined-not/#comments Sun, 25 Sep 2011 10:34:33 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11132 How do I check if a bash shell variable called $input is defined or not under BSD / Apple OS X / Unix / Linux like operating systems?]]> http://www.cyberciti.biz/faq/linux-unix-howto-check-if-bash-variable-defined-not/feed/ 1 Linux / UNIX: HowTo Empty Directoryhttp://www.cyberciti.biz/faq/howto-empty-linux-unix-directory-delete-all-files/ http://www.cyberciti.biz/faq/howto-empty-linux-unix-directory-delete-all-files/#comments Tue, 20 Sep 2011 21:14:33 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11109 How do I empty a directory (delete all files) under Linux / Unix without deleting directory itself?]]> http://www.cyberciti.biz/faq/howto-empty-linux-unix-directory-delete-all-files/feed/ 7 KSH: Import File With Variables and Functionshttp://www.cyberciti.biz/faq/unix-linux-import-file-in-ksh-call-ksh-script/ http://www.cyberciti.biz/faq/unix-linux-import-file-in-ksh-call-ksh-script/#comments Tue, 20 Sep 2011 20:05:13 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11095 How do I import variables and functions defined in lib.ksh script to another ksh script called setup.ksh under Linux / Unix like operating systems? How do I execute commands from a file in the current KSH shell?]]> http://www.cyberciti.biz/faq/unix-linux-import-file-in-ksh-call-ksh-script/feed/ 0 Debian Linux: Change Hostname / Computer Name Permanentlyhttp://www.cyberciti.biz/faq/debian-change-hostname-permanently/ http://www.cyberciti.biz/faq/debian-change-hostname-permanently/#comments Mon, 19 Sep 2011 10:25:38 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11090 How do I change the hostname of a Debian Linux system permanently using the command line tools?]]> http://www.cyberciti.biz/faq/debian-change-hostname-permanently/feed/ 2 Linux / Unix: Bash Find Matching All Dot Fileshttp://www.cyberciti.biz/faq/linux-unix-bsd-appleosx-ksh-csh-bash-find-hidden-dotfiles/ http://www.cyberciti.biz/faq/linux-unix-bsd-appleosx-ksh-csh-bash-find-hidden-dotfiles/#comments Wed, 14 Sep 2011 06:18:12 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11078 A dot-file is generally any file whose name begins with a full stop. In Linux or Unix like operating system it is also called as hidden file. How do I list all dot files in my home directory?]]> http://www.cyberciti.biz/faq/linux-unix-bsd-appleosx-ksh-csh-bash-find-hidden-dotfiles/feed/ 4 Linux / Unix: Find Out What tty I’m Usinghttp://www.cyberciti.biz/faq/linux-unix-appleosx-bsd-what-tty-command/ http://www.cyberciti.biz/faq/linux-unix-appleosx-bsd-what-tty-command/#comments Wed, 14 Sep 2011 06:05:23 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11067 What is a tty under Linux / UNIX? How do I find out what tty I'm on?]]> http://www.cyberciti.biz/faq/linux-unix-appleosx-bsd-what-tty-command/feed/ 0 Linux: NFS4 mount Error reason given by server: No such file or directoryhttp://www.cyberciti.biz/faq/mount-nfs4-reason-given-by-server-no-such-file-directory/ http://www.cyberciti.biz/faq/mount-nfs4-reason-given-by-server-no-such-file-directory/#comments Tue, 06 Sep 2011 23:41:49 +0000 Vivek Gite http://www.cyberciti.biz/faq/?p=11006 I recently installed NFS server v4 on my HP Linux server. However, I'm not able to mount it from Linux nfs4 client using the following command:
mount.nfs4 server2:/data /data
I'm getting the following error:
mount.nfs4: mounting server2:/data failed, reason given by server: No such file or directory
How do I fix this problem?]]> http://www.cyberciti.biz/faq/mount-nfs4-reason-given-by-server-no-such-file-directory/feed/ 0