Upload
wastingtime08
View
140
Download
4
Embed Size (px)
Citation preview
RHCE "Cheat Sheet"
This document attempts to provide answers to all study points on the RHCE and RHCT ExamPreparation Guide [http://www.redhat.com/certification/rhce/prep_guide/] in a single-page (and thus,printable) format. This is not a “brain dump” or an attempt to cheat the RH302[https://www.redhat.com/courses/rh302_rhce_exam/] exam in any way. These are just my self-studynotes. Use them at your own risk.
Note: Study points last updated on 2009-08-11. This list may become out of date without notice(especially after I pass the test ).
Testing Environment with Sun VirtualBox
install guest additions:
yum install gcc kernel-develsh /media/VBOXADDITIONS*/VBoxLinuxAdditions-x86.runreboot
Prerequisite skills for RHCT and RHCE
Candidates should possess the following skills, as they may be necessary in order to fulfillrequirements of the RHCT and RHCE exams:
use standard command line tools (e.g., ls, cp, mv, rm, tail, cat, etc.)to create, remove, view, and investigate files and directories
use grep, sed, and awk to process text streams and files
use a terminal-based text editor, such as vim or nano, to modify textfiles
use input/output redirection
operator description
> redirect STDOUT to a file
2> redirect STDERR to a file
&> redirect all output to a file
2>&1 redirect all output to a pipe
use » to append instead of overwrite
understand basic principles of TCP/IP networking, including IPaddresses, netmasks, and gateways for IPv4 and IPv6
use su to switch user accounts
su - <user>
use passwd to set passwords
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 1/24
passwd <user>
use tar, gzip, and bzip2
# compress (tar/gzip)tar cvzf <file>.tgz <directory> # extract (tar/gzip)tar xvzf <file>.tgz # compress (tar/bzip)tar cvjf <file>.tbz <directory> # extract (tar/bzip)tar xvjf <file>.tbz
configure an email client on Red Hat Enterprise Linux
echo "message" | mail <email> -s "subject"mail <email> -s "subject" < <file>
use text and/or graphical browser to access HTTP/HTTPS URLs
elinkslynx
use lftp to access FTP URLs
RHCT skills
Troubleshooting and System Maintenance
RHCTs should be able to:
boot systems into different run levels for troubleshooting and systemmaintenance
append the desired runlevel to grub's kernel line:
1-5 runs appropriate rc and init scriptssingle only runs rc.sysinitemergency skips all rc and init scripts
diagnose and correct misconfigured networking
1. check /etc/sysconfig/network2. check /etc/sysconfig/network-scripts/ifcfg-<interface>3. service network restart4. chkconfig network on5. ifconfig6. ping <localhost ip>7. netstat -r8. ping <default gateway>9. ping 4.2.2.2
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 2/24
redhat network config tool:
system-config-network
diagnose and correct hostname resolution problems
1. check /etc/nsswitch.conf2. check /etc/resolv.conf3. check /etc/hosts4. dig @<dns server> google.com
redhat network config tool:
system-config-network
configure the X Window System and a desktop environment
install x:
yum groupinstall "x window system"
init respawns /etc/X11/prefdm -nodaemon to keep x running in runlevel 5startx to start manually
xfs is supposedly required for x windows (even though i can run x fine without it…):
service xfs onchkconfig xfs on
x environment config:
/etc/sysconfig/desktop/etc/X11/xinit/xinitrc/etc/X11/xinit/Xclients~/.xinitrc~./Xclients
redhat display config tool:
system-config-display [--reconfig]
install gnome desktop:
yum groupinstall "gnome desktop environment"
switchdesk allows you to change your desktop environment:
yum install switchdeskswitchdesk
if switchdesk is not available, edit /etc/sysconfig/desktop:
DISPLAYMANAGER=<GNOME|KDE|XDM>DESKTOP=<GNOME|KDE>
add new partitions, filesystems, and swap to existing systems
partitions
manage partitions:
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 3/24
fdisk <device>partprobe
filesystems
make filesystems:
mkfs.<ext2|ext3>
label filesystems:
e2label <partition> <label>blkid
manage filesystem settings:
tune2fs <partition>dumpe2fs <partition>
swap
note that it's possible to create a swap file instead of a partition:
dd if=/dev/zero of=<file> bs=1024 count=<size>
format the file/partition:
mkswap <partition|file>nano -w /etc/fstabswapon -vacat /proc/swaps
use standard command-line tools to analyze problems and configure system
check for full filesystems, quotas
Installation and Configuration
RHCTs must be able to:
perform network OS installation
at boot prompt:
linux askmethod
implement a custom partitioning scheme
configure printing
printing support is provided by cups:
service cups startchkconfig cups on
redhat printer config tool:
system-config-printer
web config tool:
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 4/24
http://localhost:631
printing via command line:
# printlpr <file># view print queuelpq# remove print joblprm <job number>
configure the scheduling of tasks using cron and at
cron
make sure vixie cron is installed and running:
yum install vixie-cronservice crond startchkconfig crond on
1. if /etc/cron.allow exists, only these users are allowed (/etc/cron.deny is ignored)2. if /etc/cron.allow does not exist, everyone allowed except users in /etc/cron.deny3. if neither exists, only root allowed4. empty /etc/cron.deny means all users allowed (default)
edit your cron jobs:
crontab -e
crontab format:
<minute> <hour> <day of month> <month> <day of week> <command>
/etc/crontab has additional user field before command.
at/batch
make sure at is installed and running:
yum install atservice atd startchkconfig atd on
1. if /etc/at.allow exists, only these users are allowed (/etc/at.deny is ignored)2. if /etc/at.allow does not exist, everyone allowed except users in /etc/at.deny3. if neither exists, only root allowed4. empty /etc/at.deny means all users allowed (default)
# add jobsat now + 1 hourat> <command> at 09:00 2009-07-23at> <command> batchat> <command>
# list jobsatq
remove jobs
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 5/24
atrm <job>
attach system to a network directory service, such as NIS or LDAP
redhat config tools:
system-config-authenticationauthconfig-tui
required packages for nis:
yum install ypbind portmap
required packages for ldap:
yum install nss-ldap openldap
configure autofs
make sure the autofs service is running:
service autofs startchkconfig autofs on
ensure the following line in /etc/nsswitch.conf:
automount: files nis
define an autofs-controlled mountpoint called test by adding the following to /etc/auto.master:
/test /etc/auto.test
create /etc/auto.test:
blah example.com:/pub/something* example:/home/&
1. local /test/blah ⇒ remote example.com:/pub/something2. local /test/user ⇒ remote example:/home/user ( this method can be used to
automount home directories)
test automounting:
ls /test/blahls /test/user # redhat defaultsls /net/<hostname>ls /misc/cd
add and manage users, groups, quotas, and File Access Control Lists
redhat user/group config tool:
system-config-users
users
/etc/passwd file format:
username:password:uid:gid:gecos:homedir:shell
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 6/24
/etc/shadow file format:
username:password:lastpwchange:minpwchange:maxpwage:pwchangewarn:inactive:expire
command line user management:
useradd <user>usermod <user>chage <user>userdel <user>pwck
default account expiration settings in /etc/login.defs
groups
/etc/group file format:
groupname:password:gid:members
command line group management:
groups <user>groupadd <user>groupmod <user>groupdel <user> grpck
quotas
install quota package
yum install quota
add fs options to /etc/fstab:
usrquota,grpquota
remount device
mount -o remount <mount point>
init quota database:
quotacheck -cugm <device>
enable/disable quotas
quotaon <device>quotaoff <device>
edit quotas
edquota -u <user>edquota -g <group>
edit grace time
edquota -ut <user>edquota -gt <group>
check/report quotas
quota <user>
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 7/24
repquota -aug
Access Control Lists
install acl package
yum install acl
add fs options to /etc/fstab:
acl
remount device:
mount -o remount <mount point>
manage acls:
# set aclssetfacl -m [d:]u:<user>:<r|w|x|-> <file>setfacl -m [d:]g:<group>:<r|w|x|-> <file> # get aclsgetfacl <file> # remove aclssetfacl -x u:<user> <file>setfacl -x g:<user> <file>setfacl --remove-all <file>setfacl --remove-default <file>
configure filesystem permissions for collaboration
1. create new group2. add users to group3. chown folder to root.<group>4. chmod folder to 2770 (g+s)
install and update packages using rpm
# installrpm -ivh <package>.rpm # updaterpm -Uvh <package>.rpm # freshen rpm -Fvh <package>.rpm # removerpm -e <package> # query by file namerpm -qf <full path of file> # verify a filerpm -Vf > <full path of file> # verify status of all packagesrpm -Va > /tmp/rpmverify
while inside the rescue environment, use the –root option to specify the real location of your rootfile system (e.g. –root=/mnt/sysimage).
properly update the kernel package
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 8/24
1. always do an install (i.e. rpm -ivh <kernel package>) rather than an update2. check /boot/grub/grub.conf for proper configuration
configure the system to update/install packages from remote repositories usingyum or pup
yum config goes in /etc/yum.repos.d/
[id]name=my repobaseurl=http://example.com/centos/enabled=1
modify the system bootloader
production config is in /boot/grub/grub.confsee examples in /usr/share/doc/grub-*/menu.lst
implement software RAID at install-time and run-time
to start, we need at least two devices/partitions of type “linux raid autodetect” (use fdisk to setpartition type to “fd”)
create raid device:
mdadm --create /dev/md0 --level=<0|1|4|5|6|10> --raid-devices=<num> <device list>
fail disk in array:
mdadm /dev/md0 -f <device>
remove disk from array:
mdadm /dev/md0 -r <device>
add disk to array:
mdadm /dev/md0 -a <device>
stop array:
mdadm --stop /dev/md0
check raid status:
mdadm --detail /dev/md0
cat /proc/mdstat
format works as usual:
mkfs.ext3 /dev/md0
don't forget to configure /etc/fstab appropriately.
use /proc/sys and sysctl to modify and set kernel run-time parameters
config is in /etc/sysctl.conf
# search through parameters
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 9/24
sysctl -a | grep <whatever># apply changes from config file immediatelysysctl -p
use scripting to automate system maintenance tasks
configure NTP for time synchronization with a higher-stratum server
redhat config tool:
system-config-date
config is in /etc/ntp.conf
synchronization configuration example:
server 0.pool.ntp.orgserver 1.pool.ntp.orgserver 2.pool.ntp.org
apply changes:
service ntpd restartchkconfig ntpd on
verify changes:
ntpq -p
RHCE skills
Troubleshooting and System Maintenance
RHCEs must demonstrate the RHCT skills listed above, and should be able to:
use the rescue environment provided by first installation CD
linux rescue
when working in non-chrooted rescue mode:mount /dev/hdc /mnt/source (to access install files on the cd/dvd)rpm commands should use the –root=/mnt/sysimage option
manually make /dev and /proc available in chrooted mode:
mount -o bind /dev /mnt/sysimage/devmount -o bind /proc /mnt/sysimage/proc
diagnose and correct boot failures arising from bootloader, module, andfilesystem errors
check in order:
1. mbr2. /boot/grub/grub.conf3. /etc/fstab4. /etc/inittab5. /etc/rc.d/rc.sysinit
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 10/24
6. /etc/rc.d/rc*.d7. /etc/rc.d/init.d/*8. /etc/rc.d/rc.local
grub errors
in general, use the last line before the error message to see where grub error'd outto find correct value for root option, type find /grub/stage1 at the grub command line (remember that all file names in grub.conf are relative to the root option)check for missing files in kernel and/or initrd lines
kernel errors
missing/corrupt initrd file results in: kernel panic - not syncing: vfs: unable to mount rootfs on unknown-blockinvalid root parameter for kernel results in: setuproot: error mounting /proc: No such fileor directory
reinstall grub to mbr:
grub-install <device>
recreate initrd:
mkinitrd <filename> <kernel version>
fix corrupt filesystem:
fsck <partition>
if fsck is unable to locate a superblock, you can specify an alternative one:
dumpe2fs <partition>fsck -b <block#> <partition>
diagnose and correct problems with network services (see Installation andConfiguration below for a list of these services)
see what's listening on what port:
netstat -ntaupe
add, remove, and resize logical volumes
redhat lvm config tool:
yum install system-config-lvmsystem-config-lvm
create physical volume:
pvcreate <device>
create volume group:
vgcreate <name> <pv device> [pv device]
extend volume group:
vgextend <name> <pv device>
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 11/24
create logical volume:
lvcreate --size <size>M --name <lv name> <vg name>
extend logical volume:
lvextend --size <size>M <device>resize2fs <device>
shrink logical volume:
resize2fs <device> <size>Mlvreduce --size <size>M <device>
remove logical volume:
lvremove <device>
diagnose and correct networking services problems where SELinux contexts areinterfering with proper operation.
enable/disable selinux in /etc/sysconfig/selinux:
SELINUX=enforcingSELINUXTYPE=targeted
install selinux troubleshooter:
yum install setroubleshootservice setroubleshoot startchkconfig setroubleshoot on
install selinux management tool:
yum install policycoreutils-gui
list selinux errors:
sealert -a /var/log/audit/audit.log | less
launch gui browser:
sealert -b
list selinux booleans:
getsebool -a
set selinux boolean:
setsebool -P <boolean> = <0|1>
list security contexts:
ls -Z <file>
change security contexts:
# using reference (copy contexts from existing known-good file)chcon -R --reference <old file> <new file>
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 12/24
# manualchcon -R -u <user> <file>chcon -R -t <type> <file>
Installation and Configuration
RHCEs must demonstrate the RHCT-level skills listed above, and they must be capable of configuringthe following network services. For each of these services, RHCEs must be able to:
install the packages needed to provide the serviceconfigure SELinux to support the serviceconfigure the service to start when the system is bootedconfigure the service for basic operationConfigure host-based and user-based security for the service
HTTP/HTTPS
install
yum install httpd mod_ssl
selinux
make new DocumentRoot match default DocumentRoot ( this applies to any directory that apachewill serve files from):
chcon -R --reference /var/www /www
start at boot
chkconfig httpd on
basic config
requirements for ~user/ directories:UserDir directivechmod 701 the user's home directorychange security context on the user's UserDir
requirements for .htaccess file usage:AllowOverride All directive
requirements for name-based virtual hosts:NameVirtualHost *:80 and NameVirtualHost *:443 directiveseach virtual host requires appropriate ServerName and ServerAlias directives
a single virtual host cannot span multiple ports (i.e. 80 and 443). two separateVirtualHost *:<port> sections are needed to do this.
self-signed ssl cert:
cd /etc/pki/tls/certsrm localhost.crtmake testcert
check virtual host config:
httpd -D DUMP_VHOSTS
host-based security
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 13/24
firewall config:
protocol ports
tcp 80, 443
hosts are allowed by default and must be explic itly denied:
<Directory /var/www/html> Order deny,allow Deny from 192.168.0.0/255.255.255.0 Deny from badguys.example.com</Directory>
hosts are denied by default and must be explicitly allowed:
<Directory /var/www/html> Order allow,deny Allow from 192.168.0.0/255.255.255.0 Allow from goodguys.example.com</Directory>
user-based security
create web password file:
htpasswd -c /etc/httpd/webusers testuser1htpasswd /etc/httpd/webusers testuser2
create web group file (/etc/httpd/webgroups):
testgroup: testuser1 testuser2
allow access by group:
<Directory /var/www/html> AuthType Basic AuthName "top secret area" AuthUserFile /etc/httpd/webusers AuthGroupFile /etc/httpd/webgroups Require group testgroup</Directory>
verify service functionality
test http/https:
elinks <http|https>://<hostname>/[path]
SMB
install
yum install samba samba-client
selinux
allow samba to share home directories:
setsebool -P samba_enable_home_dirs=1
mark a directory as sharable with samba:
chcon -R -T samba_share_t <directory>
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 14/24
start at boot
chkconfig smb on
basic config
redhat samba config tool:
yum install system-config-sambasystem-config-samba
set workgroup/domain:
workgroup = <workgroup>
security modes:
# connections check local pwdb (default)security = user
# member server on a domain, uses pwdb on a dcsecurity = domainworkgroup = EXAMPLE
# member server on an ad domain using kerberos, uses pwdb on a dcsecurity = adsrealm = EXAMPLE.COMpassword server = kerberos.example.com
# used when samba was not capable of being a domain member server (DO NOT USE)security = serverencrypt passwords = yespassword server = <netbios name of dc>
# each share requires a password (DO NOT USE)security = share
share options:
[<share name>]# path for sharepath = <path>
# share is visible browseable = <yes|no>
# rw enabledwriteable = <yes|no>
# this is a shared printerprintable = <yes|no>
# all users connecting to this share use <group> as their primary groupgroup = <group name>
join domain:
net rpc join -U root
fstab example:
//<hostname>/<share> <mountpoint> cifs user=<username>,pass=<password> 0 0
mount.cifs and umount.cifs need to be chmod'ed u+s in order to be used by non-root users
host-based security
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 15/24
firewall config:
protocol ports
tcp 139, 445
udp 137, 138
hosts allow/deny can be used per-server or per-share:
hosts allow = 127.0.0.1 192.168.2.0/24 192.168.3.0/24hosts deny = 0.0.0.0/0
user-based security
account maintenance:
# add account (local linux account must exist first, or be translated via /etc/samba/smbusers):smbpasswd -a <username> # enable/disable account:smbpasswd -e <username>smbpasswd -d <username> # remove account:smbpasswd -x <username>
service smb reload may be needed after account changes
share access:
valid users = <user1> @<group1>
share access is also controlled by unix file permissions
verify service functionality
list shares:
smbclient -L <hostname> -U <username>
browse shares:
smbclient //<hostname>/<share> -U <username>
test allow/deny statements for a host:
testparm /etc/samba/smb.conf <hostname> <ip address>
NFS
install
yum install portmap nfs-utils
start at boot
chkconfig portmap onchkconfig nfs onchkconfig nfslock onchkconfig netfs on
basic config
redhat config tool:
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 16/24
yum install system-config-nfssystem-config-nfs
format of /etc/exports:
<mountpoint> <host>(<options>) [<host>(<options>) ...]
activate new exports:
/etc/init.d/nfs restart
host-based security
edit /etc/sysconfig/nfs and restart nfs to set static ports
firewall config:
# see ports rpcinfo -p
host based security is intrinsic to the format of the exports file
user-based security
use standard file permissions
verify service functionality
list exports:
showmount -e <host>
FTP
install
yum install vsftpd
selinux
allow local users to log in and cd into home directories:
setsebool -P ftp_home_dir=1
start at boot
chkconfig vsftpd on
basic config
host-based security
use ipchains with -[!]s option
firewall config:
protocol ports
tcp 21
ftp data transfers will not work unless ip_conntrack_ftp is added to IPTABLES_MODULES in/etc/sysconfig/iptables-config
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 17/24
tcp_wrappers example:
vsftpd : 192.168.0.
user-based security
allow/deny controlled via /etc/vsftpd/user_list ( users in /etc/vsftpd/ftpusers arealways denied via pam)default allow/deny is configured by userlist_deny statement in vsftpd.conf
verify service functionality
test ftp:
ftp <server>
Web proxy
install
yum install squid
selinux
allow squid to connect to the network (this is recommended, but was not needed in my testing):
setsebool -P squid_connect_any=1
start at boot
chkconfig squid on
host-based security
firewall config:
protocol ports
tcp 3128
allow access from local networks:
acl our_networks src 192.168.1.0/24 192.168.2.0/23http_access allow our_networks
user-based security
verify service functionality
test proxy:
HTTP_PROXY=<server>:3128 elinks
SMTP
install
yum install postfixalternatives --config mtaservice sendmail stop
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 18/24
start at boot
chkconfig postfix on
basic config
listen on public interfaces:
inet_interfaces = all
specify all destination hostnames/domains:
mydestination = <hostname1>, <hostname2>, ...
specify origin domain:
myorigin = $mydomain
local aliases in /etc/aliases ( dont forget to run newaliases to apply changes):
<alias>: <user1>[, user2]
virtual aliases in /etc/postfix/virtual ( dont forget to run postmap /etc/postfix/virtual toapply changes):
<virtual alias>: <user>
enable virtual aliases:
virtual_alias_maps = hash:/etc/postfix/virtual
outbound address rewriting in /etc/postfix/generic ( dont forget to run postmap/etc/postfix/generic to apply changes):
<outbound alias>: <user>
enable outbound aliases:
smtp_generic_maps = hash:/etc/postfix/generic
host-based security
use ipchains with -[!]s option
firewall config:
protocol ports
tcp 25
user-based security
use smtp auth?
verify service functionality
test smtp:
telnet <server> 25
IMAP, IMAPS, and POP3
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 19/24
install
yum install dovecot
start at boot
chkconfig dovecot on
basic config
enable protocols:
protocols = <protocol list>
create custom ssl cert:
nano -w /etc/pki/dovecot/dovecot-openssl.cnf/usr/share/doc/dovecot-*/examples/mkcert.shservice dovecot restart
host-based security
use ipchains with -[!]s option
protocol ports
tcp 143, 110, 995, 993
user-based security
use pam_listfile in /etc/pam.d/dovecot
verify service functionality
test mailbox acess:
mutt -f <imap|imaps|pop|pops>://<user>@<server>
SSH
install
yum install openssh-server
start at boot
chkconfig sshd on
user-based security
allow/deny user access:
AllowUsers user1 user2 [email protected] user4 user5 [email protected]
host-based security
use ipchains with -[!]s option
firewall config:
protocol ports
tcp 22
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 20/24
tcp_wrappers example:
sshd : 192.168.0.
verify service functionality
test logging in:
ssh <user>@<server>
DNS (caching name server, slave name server)
install
yum install bind-chroot caching-nameserver
start at boot
chkconfig named on
basic config
copy sample config:
cp -a /var/named/chroot/etc/named.caching-nameserver.conf /var/named/chroot/etc/named.conf
caching-only nameserver:
edit listen-on directives (comment out to listen on all interfaces)edit allow-query directives (comment out allow queries from everyone)edit match-clients and match-destinations directives to allow recursive queries from otherhosts
slave nameserver:
get slave example from /usr/share/doc/bind-*/sample/etc/named.conf
host-based security
firewall config:
protocol ports
tcp 53
udp 53
allow-query example:
allow-query { 192.168.0.0/16; localnets; };
user-based security
N/A
verify service functionality
test query:
dig @<server> <domain>
test zone transfer:
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 21/24
dig @<server> <domain> axfr
NTP
install
yum install ntp
start at boot
chkconfig ntpd on
host-based security
firewall config:
protocol ports
udp 123
allow other servers to sync with us:
restrict 192.168.1.0 mask 255.255.255.0 nomodify notrap
user-based security
N/A
verify service functionality
show peers:
ntpq -p
RHCEs must also be able to:
configure hands-free installation using Kickstart
yum install system-config-kickstart
1. make installation tree available2. create kickstart file (use system-config-kickstart to create ks.cfg) and validate (using
ksvalidator)3. validate kickstart file4. make kickstart file available
bootable diskette (place in top level directory)bootable cdrom (place in top level directory)network (http, ftp, nfs)
5. use bootable media and supply appropriate kernel parameter
ks=floppy:/ks.cfgks=cdrom:/ks.cfgks=http://example.com/ks.cfgks=nfs:example.com:/ks.cfg
implement logical volumes at install-time
use iptables to implement packet filtering and/or NAT
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 22/24
do not use system-config-securitylevel, as it will overwrite your custom iptables rules. thefollowing method seems to be the best way to go:
1. make changes in /etc/sysconfig/iptables2. run /etc/init.d/iptables restart to apply changes
packet filtering
packet filtering example:
-A <chain> -p <tcp/udp> -m <tcp/udp> [-s[!] <source address>] --dport <destination port> -j ACCEPT
NAT
enable ip forwarding in /etc/sysctl.conf:
net.ipv4.ip_forward = 1
to test from another machine:
ip route replace default via <ip address>
inbound dnat:
iptables -t nat -A PREROUTING -p <tcp/udp> --dport <destination port> -j DNAT --to-dest <private server>:<port>
outbound dnat:
iptables -t nat -A OUTPUT -p <tcp/udp> --dport <destination port> -j DNAT --to-dest <private server>:<port>
masquerading:
iptables -t nat -A POSTROUTING -o <outbound interface> -j MASQUERADE
snat:
iptables -t nat -A POSTROUTING -j SNAT --to-source <public server>:<port>
use PAM to implement user-level restrictions
module documentation
/usr/share/doc/pam-*/txts
module configuration
/etc/pam.d/etc/security
<module interface> <control flag> <module name> <module arguments>
module interface description
auth user authentication (e.g. verifies password, set group membership or kerberos tickets, etc.)
account verifies that access is allowed (e.g. expired account?, check group membership, etc.)
password handles password changes
session manages user sessions (e.g. mount home dir, create mailbox, logging, etc.)
control flag description
required must pass, continue testing on failure
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 23/24
requisite must pass, stop testing on failure
sufficient failure is ignored, but if passing so far, return success at this point
optional pass or failure is irrelevant
include include another file
pam_listfile.so example
allow/deny users if listed in /etc/special:
auth required pam_listfile.so onerr=success item=user sense=<allow|deny> file=/etc/special
Additional Notes
tcp_wrappers
file format:
<daemon list> : <client list> [except <client list>] [: <option>]
search order:
1. /etc/hosts.allow2. /etc/hosts.deny3. allow by default
searching stops on first match
Troubleshooting
unable to log in
password wrong or expired?account locked?shell set to /sbin/nologin, /bin/false, etc.?root user and PermitRootLogin no in /etc/ssh/sshd_config?root user and terminal not listed in /etc/securetty?non-root user and /etc/nologin exists?check pam_listfile restrictions
rhce.txt · Las t modified: 2009/08/25 07 :44 by admin
Except where otherwise noted, content on this wiki is licensed under the following license:CCAttribution-Noncommercial-Share Alike 3.0 Unported [http://creativecommons.org/licenses/by-nc-sa/3.0/]
8/16/2010 rhce [Mike Conigliaro's Wiki]
http://conigliaro.org/wiki/rhce 24/24