MarkD's knowledge base for Unix

General

• Changing a process' priority
  % renice priority pid
  the higher the number, the lower scheduling priority will be used.

• Changing all *.html files to *.adp
  % ~/bin/rename.pl 's/.html/.adp/' *.html

• Changing filenames to lower case
  % ~/bin/rename.pl 'tr/A-Z/a-z/' *

• Determining the runlevel on solaris
  /bin/who -r

• Directory space consumption
  To see how much disk space a directory consumes, use
  % du -sk dir_name

• Doing a recursive FTP
  Get ncftp. Make a local directory (say urlgle) to store the incoming. then run
  % ncftpget -R -u username -p password host urgle /

• Doing something to a hierarchy of files
  To do something to all of the html files in a directory (e.g. to grep something) % cd directory
% find . -name "*.html" -exec grep Spoon {} ; -print
Don't forget the dot right after find, and the {} construct.

• Enabling core files under linux
  bash$ ulimit -c unlimited

• Getting a count from grep
  % grep -c gethandle *.tcl

• Help! My Filesystem is full!
  See my filesystem document.

• How do I find out IP addresses on Solaris
  % ifconfig -a

• How do I find out todays date in seconds-since-the-epoch
  On Linux, do
  % date '+%s'

• How do I unzip in a pipeline?
  if you don't have gzcat, use the -c option for gunzip:
  % gunzip -c blah.tar.gz | tar xf -

• Moving a directory hierarchy
  cp -r does not work for moving a directory hierarchy since it doesn't honor symbolic links (you end up with a copy of the file for each sym link). Instead, you'll need to do a "push-pull" tar using a pipe. To move /tmp/blarg to /var:
  % cd /tmp
% tar cvf - blarg | (cd /var; tar xf -)

• Multiple IP addresses
  (for Linux at least)
  # ifconfig eth0:1 192.168.100.43

• Rebooting a Solaris machine
  # shutdown -i 6 -y -g 0

• Replacing a string in a set of files
  perl -pi.bak -e 's/OLDSTRING/NEWSTRING/g' *.html

• Restricting Find to only deal with files (not directories)
  find . -type f -name "*.html" -exec grep Spoon {} ; -print

• Running a command on a set of files
  In a Bourne-shell type environment:
  $ for file in *; do
> wc -l $file;
> done


• Running a pipeline in sudo
  % sudo sh -c "tar cf - * | (cd /mirror4/web; tar xf -)"

• See what processes have network sockets open
  # netstat -tupan

• Seeing # of processors on Solaris
  % psrinfo

• Seeing who did with with sudo
  look in /var/log/authlog

• Show what processes have a socket open
  % sudo netstat -anp --protocol=inet

• Tarring a large number of files based on some criteria
  find + xargs won't work since xargs has a limit on command line size, so it'll invoke multiple tar commands, thereby blasting over the previously created archive.

  bash -c 'tar cf /tmp/touchmymonkey.tar `find . -newer /some/file/to/compare/timestamps/with | grep "^.$"`'
  

  The grep is necessary to prevent double-addition of files.

• Tarring through an ssh pipe
  % cd DIRECTORY
% tar cf - . | gzip | ssh dev0103-003 "cd /web/greentravel-dev; gunzip | tar xf -"

• Upading DNS
  

  # vi /var/named/db.arsdigita.com
    find markd
    change IP to the one you want
    go to top of file
      change the serial number to something appropriate
        the format is YYYYMMDD so if isn't today, change it to today.
  # ps -ef | grep named
  # -HUP the named process.
  # nslookup and see if it's there.
    if not, find rolf and whine

• Updating an rpm
  rpm -Uhv

• Using Image Magick to scale an image proportionally
  % find . -name "*.jpg" -exec convert -verbose -geometry 150x150 {} {} ;

• Using find for multiple -name clauses
  % find . ( -name "*_itin.htm" -o -name "*_faq.htm" ) -exec `pwd`/strip-junk.tcl {} ;

• Where can I get gmake?
  To build the Oracle Driver for AOLserver you need gmake. ftp it from a GNU mirror:
  ftp://aeneas.mit.edu/pub/gnu/make/make-3.77.tar.gz
  or snarf it from
  http://markd.arsdigita.com/misc

• debugger/threads on Solaris
  gdb doesn't seem to work. dbx seems happier
  (dbx) threads
(dbx) thread -info t@threadnum

• finding setuid and setgid files
  % find . -type f ( -perm 04000 -o -perm -02000 ) -print

• removing files with "-" in them
  % rm -- -bad-file-name

• using ssh without a password
  for things like remote cvs.

  1.on the remost host login as nsadmin and run ssh-keygen with no
                passphrase to create ~/.ssh/identity and ~/.ssh/identity.pub 
             2.copy identity.pub to the repository host and append it to
                ~nsadmin/.ssh/authorized_keys 
             3.chmod 400 ~nsadmin/.ssh/authorized_keys