Linux admin quick reference

LINUX Admin Quick Reference
Jialong He
Jialong_he@bigfoot.com http://www.bigfoot.com/~jialong_he

/etc/NETWORKING (Slackware) /etc/sysconfig/network (Redhat) etc/resolv.conf /etc/hosts /etc/host.conf

boot and the name is read from these files. May change manually.

HOSTNAME=hostname.domain.com

User Management Files
/etc/group /etc/passwd /etc/shadow /etc/bashrc /etc/profile$HOME/.bashrc $HOME/.bash_profile /etc/csh.cshrc /etc/csh.login $HOME/.cshrc $HOME/.tcshrc $HOME/.login /etc/skel /etc/default /etc/redhat-release /etc/slackware-version User account information.

specify name server, DNS domain and search order. For Example: search la.asu.edu nameserver 129.219.17.200 host name to IP mapping file. host name information look up order. Example: order hosts, bind multi onnew way to specify information source. TCP/IP services and ports mapping. RPC service name to their program numbers mapping.

NFS File Sharing Files
/etc/fstab /etc/exports /etc/auto.master file systems mounted during boot. NFS server export list. auto mount master file.

Commands
mount exportfs showmount –e hostname mount a file system or all entries in fstab. export file system listed inexports show file systems exported

bash system wide and per user init files. /etc/nsswitch.conf /etc/networks /etc/protocols /etc/services /etc/rpc template files for new users. default for certain commands. Redhat/Slackware version info (Linux kernel version with “uname –a”)

tcsh system wide and per user init files.

Printer Configuration Files
/etc/printcap /etc/printcap.local Printercapabilities data base. LPRng configuration file. permissions control file for the LPRng line printer spooler Access control (BSD lpd). trusted hosts. Environment variable of default printer. parallel port.

Commands
netconfig pppsetup menu driven Ethernet setup program. setup PPP connection (Slackware). setup Ethernet during boot, for example

/etc/lpd.conf /etc/lpd.perms /etc/hosts.lpd/etc/hosts.equiv PRINTER /dev/lp0

Commands
adduser useradd, userdel, usermod newusers groupadd, groupdel, groupmod chage. ch fn, chsh script to create an new user interactively (slackware) or link to useradd (Redhat). create, delete, modify an new user or update default new user information.. update and create new users (batch mode). add, delete or modify group. modify account policy (passwordlength, expire data etc.) or finger information (full name, phone number etc.) change default login shell. gain root access during boot prompt without password, can be used to fix some problems. mount –w -n –o remount / host arping; arp ipchains iptables ifconfig

/sbin/ifconfig eth0 ${IPADDR} broadcast ${BROADCAST} netmask ${NETMASK} /sbin/route add -net ${NETWORK} netmask ${NETMASK} eth0/sbin/route add default gw ${GATEWAY} netmask 0.0.0.0 metric 1 lookup host name or IP (similar to nslookup). find out Ethernet address by first arping then arp. firewall and NAT (/etc/sysconfig/ipchains on Redhat) firewall and NAT (/etc/sysconfig/iptables on Redhat) dnsdomainname show DNS domain name.

Commands
lpc, lpq, lprm line printer control program, print queue maintain

Sendmail Filessendmail.cf sendmail.mc “sendmail.cf” is the configuration file. “sendmail.mc” is a macro file which can be used to generate “sendmail.cf” by: m4 sendmail.mc > sendmail.cf mail aliases, must run “newaliases” after change. use :include: to include external list in a file. mail access control, FEATURE(access_db) should be set in sendmail.mc. For example, in /etc/mail/access cyberpromo.com REJECT mydomain.comRELAY spam@somewhere.com DISCARD makemap hash /etc/mail/access < /etc/mail/access /etc/mail/relay- list all host/domain accepted for relaying.

linux init=/bin/sh rw

Network Configuration Files
/etc/rc.d/rc.inet1 (Slackware) /etc/sysconfig/neworkscripts/ifcfg-eth0 (Redhat) /etc/HOSTNAME IP address, Network mask, Default gateway are in these files. May edit manually to modify network...