Linux General

NetworkSettings

LinuxMiscellany

Commands

du -hx --max-depth=1
xauth merge ~/.Xauthority
2>&1

Current kernel boot parameters

cat /proc/cmline

Find a running process The first character in brackets is the key, let's you avoid the grep -v grep, etc.

ps aux (or -elf) | grep '[a]ny_.*_process'

File/directory with spaces or special characters:

cd dir\ with \ spaces
cd ./-dont_do_this

For Loops

for i in item1 item2 item3 ; do something ; done
for i in `cmd` ; do something ; done
for i in {1..9} ; do something ; done
for i in `seq start increment end` ; do something ; done
for ((init, condition, increment)); do something ; done

Fixing filesystem errors:

Ext3	fsck -y {mount point}
GFS	gfs_fsck {mount point}

Bad superblock errors:

Ext3

dumpe2fs {mount point}

In output look for “Backup superblock”

e2fsck -b {backup superblock} {mount point}

Determine if disk is dirty and fsck required:

Look for state not equal “clean”

dumpe2fs {path_to_block_device} | grep state

Set

set -o vi sets editor to vi set -vx sets command tracing (+vx to turn off)

Select

select i in list ; do something ; done

Telnet

Escape out of telnet or Xen console = Ctrl+]

AWK

awk -F{delim} '/search_pattern/ { print $1 }'

Job Control

Background running job

xeyes

^Z

bg

Less

vi from less/more = v

Boot Issues

No boot - grub prompt

rescue mode

grub-install boot_device (ie /dev/sda)

No boot - corrupt grub

root(hd0,0) = hd#,part#

setup(hd0)

exit

Cron

crontab: minute hour dayofmonth month dayofweek command

Calc

Calc (simple):

echo $[ a + b ]

Calc (better):

echo "a / b" | bc

Big File

Make big file:

dd if=/dev/zero of=bigfile bs=1k(1M) count=N

SSH

SSH tunnelling on gumstix:

ssh -L 443:192.168.1.100:22 -g localhost

remote:

ssh mtonneson.homelinux.org -p 443

RHEV

HOST: RHEL AP 5.4 with KVM and libvirt installed.

Have to do a yum erase libvirt for RHEV-M install to work.

Failed to create RHEVM bridge - needed to reinstall.

No message or warning regarding auto-rebooting RHEL HOST - NOT GOOD!

Reinstall from “click here” does not work - endless loop - must activate-

must put into maintenance - then can't connect. Only way is to deleteand re-add.

FC - powerpath works but can't filter out emcpower in lvm.conf or thedisk creation will fail, in RHEV-M

RHCE

RHCE Study Topics

Local users & groups
Cron/crontab
tcpwrappers
SELinux
NFS server
vsftpd
sendmail/postfix
apache
dhcpd

Boot Process

Kernel loads

Writes to /var/log/messages

Starts init daemon

Reads /etc/inittab

Runs /etc/rc.d/rc.sysinit

Runs /etc/rc.d/rc.local

rc.sysinit logs to /var/log/dmesg

Additional logging to /var/log/boot.log

man pages

man1	cmds all users can access
man2	kernel errors & system subroutines
man3	library of subroutines
man4	network protocols, devices and drivers
man5	formatting info
man6	games and demos
man7	misc
man8	cmds only root can access
man9	linux kernel

man -a <keyword> = shows all pages matching keyword

Apache

program root - usually /etc/httpd/conf or /usr/local/apache web root - usually /home/httpd or /var/www/htdocs config file - httpd.conf

apachectl - control script

start/stop/restart

graceful - continues current child procs before restart

configtest - tests syntax of httpd.conf

status/fullstatus

inetd

inetd

/etc/services - lists network services and ports
/etc/inetd.conf - config file

xinetd

/etc/xinetd.conf - config file
/etc/xinetd.d/ - service specific parameter files

Debian

Debian package mgmt

dpkg
--install - install package
--remove - remove package
--print-avail - general info about package
--list - list installed packages
--listfiles - list files installed by package
--status - full package details
--search - which package owns/installed file

/var/lib/dpkg/available - available packages
/var/lib/dpkg/status - package status

dselect - menu driven version of dkpg
apt-get - cmdline package installer
alien - package converter

ARCHIVE INFO BELOW

ARCHIVE INFO BELOW

RHEL 3

RHEL3 local login w/o LDAP:

Try adding the following to nss_initgroups_ignoreusers line
to the file /etc/ldap.conf:

Just assume that there are no supplemental groups for these named users nss_initgroups_ignoreusers root,ldap,named,avahi,haldaemon,dbus,radvd,tomcat,radiusd,news,mailman,ntp,smmsp,xfs

RH online virts

RH Virtualization

aws.amazon.com
ec2
SPEC Virt
overt.et.redhat.com

LDAP

passwd: ldapsearch -x -v -h directory -b “o=domain.com” “uid=UID”

CDROM from HP iLO

VM install = cdrom://hdc:/mnt/source

VMWare

vmware-cmd -l | xargs -ipath -t -e vmware-cmd path getpid

Installing VMware Tools in a Linux Guest

Choose Settings > VMware Tools Install, then click Install. This step connects the virtual machine's CD-ROM drive to an ISO image file on the ESX Server machine.

In your Linux guest, become root, mount the VMware Tools virtual CD-ROM, copy the installer file from the virtual CD-ROM to /tmp, then unmount the CD-ROM.

mount -t iso9660 /dev/cdrom /mnt
cp /mnt/vmware-linux-tools.tar.gz /tmp
umount /dev/cdrom

Untar the VMware Tools tar file in /tmp and install it.

cd /tmp
tar zxf vmware-linux-tools.tar.gz
cd vmware-tools-distrib
./vmware-install.pl

Note: When installing VMware Tools in some versions of Linux, the installer will need to recompile VMware Tools. For this to work, you need to have a C compiler installed in the guest. In some cases you may get compiler warning messages during the VMware Tools installation. However, the control panel and drivers still work correctly.

Follow the remaining steps. Choose directories for the various files. Choose a display size for the virtual machine. Enter the number for the choice and press Enter. If you wish, start X and your graphical environment and launch the VMware Tools background application.

vmware-toolbox &

Note: If you created this virtual machine using the vmxnet driver, you now need to run netconfig or another network configuration utility in the virtual machine to set up the virtual network adapter.

HP RSM

During operation, the service logs events from the infrastructures on tty1 through tty10 (if available), as well as /var/log/messages. If this produces too much text on the screen, adding the option “-V0x0” to the hprsm startup script will silence the text.

Host rename

Server rename

/etc/hosts
/etc/sysconfig/network
/usr/openv/netbackup/bp.conf
Restart nscd service

Samba client

smbclient //windows/share -W activedirectory.domain.com -U username
mount -t smbfs -o username=user,workgroup=activedirectory.domain.com
//server/share /mnt/smb

RHEL 4 upgrade on VMWare

Upgrade VM RHEL4.0 -> RHEL4.2

cp {BusLogic}.ko /root/

shutdown

Connect floppy and CD

LSILogic -> {BusLogic}

Update to RHEL4.2 (linux dd text)

boot linux rescue

cp /etc/modprobe.conf.anacbak /etc/modprobe.conf

add 'alias scsi_hostadapter {BusLogic}' to modprobe

cat /etc/issue.rpmsave > /etc/issue

cp /root/BusLogic.ko /lib/modules/2.6.9-22.EL/kernel/drivers/scsi/

mkinitrd -v -f /boot/initrd-2.6.9-22.EL-buslogic.img 2.6.9-22.EL

edit grub.conf - add new initrd

reboot

/usr/bin/vmware-config-tools.pl