this is obsolete doc -- see http://doc.nethence.com/ instead

Miscellaneous Unix tips (doesn’t fit anywhere else) 

Clean up comments 

Strip down your config files e.g. for Redhat LVM2, 

cp lvm.conf lvm.conf.dist

sed '

/^[[:space:]]*$/d;

/^[[:space:]]*#/d;

' lvm.conf.dist > lvm.conf

Broken links 

Look for broken links, 

find . -type l | (while read FN ; do test -e "$FN" || ls -ld "$FN"; done)

Clean up old logs or backups 

Remove those older than 6 days, 

find /var/dir -type f -name "*.log" -mtime +5 -exec rm -f {} \;

Report syslog messages 

When copy/pasting syslog messages to send them by email, you may want to clean the headers first, 

vi inputfile #paste here

sed 's/^...  [^:]*:[^:]*:[^:]* \(.*\): \(.*\)/\1: \2/' inputfile

Whole system with tar 

Prepare the exclude list, 

mkdir -p /var/backup

cat > /exclude.list <<EOF9

/dev

/proc

/root

/sys

/var/backup

EOF9

Launch the backup, 

cd /

tar cz -X /exclude.list -f /var/backup/backup.tar.gz .

To restore, boot with a rescue media (for example slackware install) and, 

tar xzf /var/backup/backup.tar.gz -C /

Code format 

Format your code with GNU indent (http://www.gnu.org/software/indent/). 

Convert tabs to spaces with GNU coreutils (http://www.gnu.org/software/coreutils/), 

mv file file.dist

expand file.dist > file

Proxy config 

export http_proxy=http://USERNAME:PASSWORD@proxy.example.net:8080

export https_proxy=$http_proxy

export ftp_proxy=$http_proxy

lynx www.google.fr

Note. yes, 'http: //' for ftp_proxy 

Note. on C shells, use setenv instead 

Device busy 

Determine what's using a file, directory or mount point, 

fuser -u /data

kill the processes, 

fuser -ku /data

Note. -m might be helpful too 

Search 

Search for files changed between 0 and 1 minute before, 

find . -cmin 1

between 1 and 2 minute before, 

find . -cmin 2

Permissions 

This may or may not work on all UNICES. To fix the permissions accordingly to file and directories, 

find . -type d -exec chmod 755 {} \;

find . -type f -exec chmod 644 {} \;

Note. there's also '-type l' on GUN/Linux distros 

Using cpio 

Create a cpio archive, 

cd folder/

find . | cpio -ocm > ../archive.cpio

#find . | cpio -co | gzip -9 > ../initrd.img

#(find . | cpio -co | gzip -9) > ../initrd.img

Extract an archive, 

mkdir -p folder

cd folder/

cpio -icdm < ../archive.cpio

#gzip -dc ../initrd.img | cpio -id

Time & date 

Beside distribution's specific way to setup time, there's always NTP, 

ntpdate -u ntp.obspm.fr

Note -u behind firewalls. -b at boot time. -s to report to syslog or >/dev/null to stay quiet. 

Add this to root's conrtab (crontab -e), 

0 6 * * *       ntpdate -u -s ntp1.dedibox.fr >/dev/null

Or the NTP daemon, 

ntpq -q

Crontab 

Good old crontab way works everywhere (no freacking /etc/cron.*), 

crontab -e

The ‘at’ job scheduler 

To plan the execution of a command at a precise time, 

at 20070818

... ^D

To check, 

atq

To remove the AT job, 

atrm

Tricky usermod 

To add a secondary group for some user, best practice is to edit /etc/group directly, 

vi /etc/group

because with usermod, you need to reenter the existing secondary groups : "usermod -G group2,group3 username" 

Note. -g for primary group, or simply vipw 

Note. -a to append a secondary group is available on Linux, not HP/UX. 

Usual commands 

Identify what user you are and in what primary group you're in, 

whoami; id

who; w

uname

netstat

top

Check services' ports, 

lsof -i:3260

netstat -apne | grep 3260

netstat -tulpn | grep 3260

Go to the last folder you where in, 

cd -

Misc 

To turn a process into a daemon, 

nohup ...

Otherwise use Daemon (http://libslack.org/daemon/) 

Mesure how much time a command takes, 

time command...

Troubbleshooting 

"strace" may be helpfull, 

strace command

References 

Unix Sysadmin Cross Reference : http://www.unixporting.com/quickguide.html 

UNIX® Load Average Part 1: How It Works : http://www.teamquest.com/resources/gunther/display/5/index.htm 

Solaris versus HP-UX : http://www.loudermilk.org/software/solaris-hpux.html 

Unix Toolbox : http://cb.vu/unixtoolbox.xhtml 

UNIX in a Nutshell: System V Edition. : http://docstore.mik.ua/orelly/unix/unixnut/ch04_03.htm