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Chapter 16 Administration Tasks

Chapter 16 Administration Tasks. Configuring User and Group Accounts Backing Up Files Scheduling Tasks System Reports Keeping Users Informed Solving Problems Helping When a User Cannot Log In Speeding Up the System Monitoring Disk Usage Disk Quota System

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Chapter 16 Administration Tasks

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  1. Chapter 16 Administration Tasks • Configuring User and Group Accounts • Backing Up Files • Scheduling Tasks • System Reports • Keeping Users Informed • Solving Problems • Helping When a User Cannot Log In • Speeding Up the System • Monitoring Disk Usage • Disk Quota System • syslogd: Logs System Messages

  2. Configuring User and Group Accounts • system-config-users • useradd (adduser) • userdel • groupadd • groupmod

  3. useradd • Adds a user account # useradd –g 500 –c “Alex Watson” alex • /etc/login.defs – creates home directory • /etc/skel – puts in default startup scripts • .bashrc • .bash_profile • .xinit, etc • userdel – deletes a user, home directory, all files • usermod – modifies a users properties # usermod-e “12/31/04” rtfm

  4. groupadd • Adds a group # groupadd –g 1024 rtfm • groupmod – modifies group properties # groupmod –g 1025 rtfm # groupmod –n manuals rtfm • groupdel – deletes a group (but not members)

  5. Backing up Files • Extremely important function of system administrators of any system • Choosing a medium • Tape is most popular based on cost per MB/GB • CDROM/DVD • Other disks

  6. Backup utilities • tar – tape archive • Anyone can use, default is to tape • tar --help for list of options $ tar –ztvf /dev/st0 OR $ tar --gzip --list --verbose --file /dev/st0 • cpio – copy input output • More popular than tar, easier to use $ cpio –ivmd /home

  7. Performing backups with tar and cpio • tar tar c `find / -mtime –1 ! –type d –print` • cpio find / -mtime –1 | cpio –o > /dev/rmt1 • taper Graphical interface backup utility used with RH Linux

  8. Restoring with tar and cpio • tar tar –xp /home/mydirectory • cpio cpio -im `*bethany.txt$` < /dev/rmt0 • Viewing tape contents: tar –cv / > /tmp/backup.TOC find / -print | cpio –cv > /dev/rmt0 2> /tmp/backup.TOC

  9. dump/restore • – sys admin only tool • Used to backup files • Can use one of 10 levels • Each level defers to previous level • 0 is full backup, 1-9 are less than full • Incremental or differential

  10. Scheduling tasks • cron and crontab • Runs routine tasks • Can schedule by minute, hour, day, date, day of week, month • at • Runs occasional tasks • Schedule each task only once $ at 3am tomorrow at> reboot at> Control D Job 1 at 2005-04-07 0:300 • kcron – kde cron GUI

  11. System Reports • vmstat - reports virtual memory statistics • top – lists top cpu intensive jobs/processes • ktop – kde GUI version of top

  12. Keeping users informed • write • talk • wall • email • mesg y or n

  13. Creating Problems • Failing to perform regular backups • Failing to test to see if backups are good!!! • Not reading and following instructions (rtfm) • Failing to ask for help when instructions are not clear • Deleting or mistyping a critical file/command

  14. Solving Problems • When a user cannot log in • Who is affected • Check caps lock key • Make sure user if valid (passwd file entry) • Change user’s password • Check user’s startup files • Check hardware connections • check configuration files

  15. Speeding up your system • Check memory • Check hardware settings/configurations • Check disk • Check network components • Check for viruses, worms, etc. • Check firewall settings

  16. Find open files • Use lsof (ls for open files) zombies • Use lsof –sp pid to find zombie processes • Or ps aux and look for old processes that do not have the owner logged on • Use –rn to check each n seconds.

  17. Keep a machine log • Keep a log of all reported problems • Review the log to see if there is a trend • Use the log to see how you may have fixed old problems – especially if they return

  18. Keep the system secure • Use shadow passwords using MD5 • Do not use the default linux/unix encryption • Check your user’s passwords with crack or cops or johntheripper • Use CERT

  19. Monitor disk usage • df – to check free space • du – to check disk usage • Use –h option for “human readable” output in KB, MB, GB rather than block usage. • Use logrotate to rotate your old logs so they don’t get too large • Check for old un- or seldom used files and archive them

  20. Removing unused space • Defragment your disks regularly • ext2/ext3 minimize fragmentation but can’t prevent it entirely • Use 3rd party defragmentation software or • Manually defrag using copy and move commands

  21. Log system messages • Controlled by syslogd – system log daemon • Selectors: • auth authpriv cron daemon kern • lpr mail news user uucp local0-local7 • Priority • debug info notice warning • err crit alert emerg (panic) • Actions: • Log • Send to console • Send to file • Send to email address

  22. Any Questions?

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