Now I am going introduce you to a set of commands & System Admin Tools that may come handy<\/p>\n
FIND<\/strong><\/p>\n [bash] find -perm 755 -type f -exec chmod 644 {} \\; #Command to change all the folders under present directory with 755 to 644<\/p>\n find -type d -maxdepth 3 -exec cp file {} \\; #Copy file to 3 levels of directories below the present directory<\/p>\n find . -name “*.trn” -ctime +3 -exec rm -f {} \\; #Forcible remove files with .trn extension and 3 days old.<\/p>\n find . -cmin -5 #Find all files created or updated in the last five minutes:<\/p>\n [\/bash]<\/p>\n (Great for finding effects of make install)<\/p>\n LS<\/strong><\/p>\n [bash]<\/p>\n ls -lSh #List files by their size<\/p>\n ls -ltr #List files by date<\/p>\n ls -F #Appends a symbol after files and directories<\/p>\n [\/bash]<\/p>\n RSYNC<\/strong><\/p>\n [bash]<\/p>\n rsync -e ssh -az \/currentdirectory IP:\/remotedirectory #Sync remote directory with our current directory.<\/p>\n rsync –bwlimit=1000 fromfile tofile #Locally copy with rate limit<\/p>\n [\/bash]<\/p>\n GPG<\/strong><\/p>\n [bash]<\/p>\n gpg -c file #Encrypt file<\/p>\n gpg file.gpg #Decrypt file<\/p>\n [\/bash]<\/p>\n DF<\/strong><\/p>\n [bash]<\/p>\n du -h –max-depth 1 #Show disk space used by all the files and directories.<\/p>\n du -s * | sort -k1,1rn | head #Show top disk users in current directory.<\/p>\n df -h #Show free disk space<\/p>\n df -i #Show free inodes<\/p>\n [\/bash]<\/p>\n Add system swap space for virtual memory paging used for System Admin Tools<\/p>\n Swap space may be a swap partition, a swap file or a combination of the two. One should size swap space to be at least twice the size of the computer’s RAM. (but less than 2GB)<\/p>\n [bash]<\/p>\n dd if=\/dev\/zero of=\/swapfile bs=1024 count=265032 – #Create file filled with zeros of size 256Mb<\/p>\n mkswap \/swapfile #Create swap file<\/p>\n swapon \/swapfile #Begin use of given swap file.<\/p>\n [\/bash]<\/p>\n Assign a priority with the “-p” flag.<\/p>\n [bash]<\/p>\n swapon -s #List swap files<\/p>\n scat \/proc\/swaps #Same as above<\/p>\n [\/bash]<\/p>\n This example refers to a swap file. One may also use a swap partition. [bash]<\/p>\n \/swapfile swap swap defaults 0 0<\/p>\n [\/bash]<\/p>\n Note: To remove the use of swap space, use the command swapoff. If using a swap partition, the partition must be unmounted.<\/p>\n Debugging System Admin Tools<\/strong><\/p>\n [bash]<\/p>\n strace -c ls >\/dev\/null #Summarise\/profile system calls made by command<\/p>\n strace -f -e open ls>\/dev\/null #List system calls made by ltrace -f -e getenv ls >\/dev\/null #List library calls made by command<\/p>\n lsof -p $$ #List paths that process id has open<\/p>\n lsof -p PID #List paths PID has open<\/p>\n lsof ~ #List processes that have specified path open<\/p>\n last reboot #Indicates last reboot time<\/p>\n [\/bash]<\/p>\n renice +15 PID #To give lower priority for a PID -19 is highest and +20 is lowest<\/p>\n To check number of IP’s connecting to port 80<\/p>\n [bash]<\/p>\n netstat -tanpu |grep :80 |awk {‘print $5’} |cut -d: -f1 |sort -n |uniq -c<\/p>\n tcpdump not port 22 #To show network traffic except on port 22<\/p>\n [\/bash]<\/p>\n Perl Administration using System Admin Tools<\/strong><\/p>\n Installation of perl module can be done from tar file.<\/p>\n [bash]<\/p>\n tar xzf yourmodule.tar.gz #Untar Module<\/p>\n perl Makefile.PL #Build with PERL makefile:<\/p>\n make<\/p>\n make install #Install<\/p>\n [\/bash]<\/p>\n You can also do this from cpan shell<\/p>\n [bash] autoconfigure<\/p>\n cpan> install URI<\/p>\n cpan> i \/PerlMagick\/ #Inquire about module. (Search by keyword)<\/p>\n Distribution J\/JC\/JCRISTY\/PerlMagick-5.36.tar.gz<\/p>\n Module Image::Magick (J\/JC\/JCRISTY\/PerlMagick-5.36.tar.gz)<\/p>\n cpan> install Image::Magick<\/p>\n cpan>force install Image::Magick #Install a module forcefully.<\/p>\n [\/bash]<\/p>\n YUM :RPM Updater<\/strong><\/p>\n YUM (Yellowdog Updater, Modified) is a client command line application for updating an RPM based system from an internet repository (YUM “yum-arch” server) accessible by URL (http:\/\/xxx, ftp:\/\/yyy or even file:\/\/zzz local or NFS)<\/p>\n [bash] yum remove package-name #To remove package<\/p>\n yum list #To list available packages version and state<\/p>\n yum list extras #To list packages not available in repositories but listed in config file<\/p>\n yum list obsoletes #To list packages which are obsoleted by repositories<\/p>\n yum clean all #To list packages which are obsoleted by packages in yum repository<\/p>\n yum update #Update all packages on your system<\/p>\n yum update package-name #Update a package<\/p>\n yum update package-name-prefix\\* #Update all with same prefix<\/p>\n [\/bash]<\/p>\n You can add new repos in \/etc\/yum.repos.d with files named file.repo For the option “gpgcheck=1” to work, use the “rpm –import GPG-KEY<\/p>\n [bash] rpm –import \/usr\/share\/rhn\/RPM-GPG-KEY-fedora<\/p>\n File: \/etc\/yum.repos.d\/fedora.repo with following entry<\/p>\n [base]<\/p>\n name=Fedora Core $releasever – $basearch – Base<\/p>\n #baseurl=http:\/\/download.fedora.redhat.com\/pub\/fedora\/linux\/core\/$releasever\/$basearch\/os\/<\/p>\n mirrorlist=http:\/\/fedora.redhat.com\/download\/mirrors\/fedora-core-$releasever<\/p>\n enabled=1<\/p>\n gpgcheck=1<\/p>\n [\/bash]<\/p>\n Additional Commands <\/p>\n [bash]<\/p>\n tzselect #To change time zone of the machine<\/p>\n command 2>&1 | tee outputfile.txt #Output of a command is send to a text file<\/p>\n wget –mirror http:\/\/www.example.com #To mirror a site<\/p>\n wget -c http:\/\/www.example.com\/largefile #To continue downloading partially downloaded file<\/p>\n [\/bash]<\/p>\n Many more tricky commands to be updated soon based on System Admin Tools for more visit<\/p>\n
find -perm 777 -type d -exec chmod 755 {} \\; #Command to change all the folders under present directory with 777 to 755<\/p>\n
Make entry to \/etc\/fstab to permanently use swap file or partition.<\/p>\n
command<\/p>\n
perl -MCPAN -e shell #First time through it will ask questions Answer “no” to the first question for<\/p>\n
yum -y install package-name #To install a package along with its dependencies<\/p>\n
rpm –import \/usr\/share\/rhn\/RPM-GPG-KEY<\/p>\n