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UNIX TOOLBOX
Unix Toolbox
This document is a collection of Unix/Linux/BSD commands and tasks which are useful for IT work or for advanced users. This is a practical guide with concise explanations, however the reader is supposed to know what s/he is doing.
SystemHardware | Statistics | Users | Limits | Runlevels | root password | Compile kernel Running kernel and system information# uname -a # Get the kernel version (and BSD version) # cat /etc/SuSE-release # Get SuSE version # cat /etc/debian_version # Get Debian versionUse /etc/ DISTR-release with DISTR= lsb (Ubuntu), redhat, gentoo, mandrake, sun (Solaris), and so on.
# uptime # Show how long the system has been running + load # hostname # system's host name # hostname -i # Display the IP address of the host. # man hier # Description of the file system hierarchy # last reboot # Show system reboot history Hardware InformationsKernel detected hardware# dmesg # Detected hardware and boot messages # lsdev # information about installed hardware # dd if=/dev/mem bs=1k skip=768 count=256 2>/dev/null | strings -n 8 # Read BIOS Linux# cat /proc/cpuinfo # CPU model # cat /proc/meminfo # Hardware memory # grep MemTotal /proc/meminfo # Display the physical memory # watch -n1 'cat /proc/interrupts' # Watch changeable interrupts continuously # free -m # Used and free memory (-m for MB) # cat /proc/devices # Configured devices # lspci -tv # Show PCI devices # lsusb -tv # Show USB devices # lshal # Show a list of all devices with their properties # dmidecode # Show DMI/SMBIOS: hw info from the BIOS FreeBSD# sysctl hw.model # CPU model # sysctl hw # Gives a lot of hardware information # sysctl vm # Memory usage # dmesg | grep "real mem" # Hardware memory # sysctl -a | grep mem # Kernel memory settings and info # sysctl dev # Configured devices # pciconf -l -cv # Show PCI devices # usbdevs -v # Show USB devices # atacontrol list # Show ATA devices Load, statistics and messagesThe following commands are useful to find out what is going on on the system.# top # display and update the top cpu processes # mpstat 1 # display processors related statistics # vmstat 2 # display virtual memory statistics # iostat 2 # display I/O statistics (2 s intervals) # systat -vmstat 1 # BSD summary of system statistics (1 s intervals) # systat -tcp 1 # BSD tcp connections (try also -ip) # systat -netstat 1 # BSD active network connections # systat -ifstat 1 # BSD network traffic through active interfaces # systat -iostat 1 # BSD CPU and and disk throughput # tail -n 500 /var/log/messages # Last 500 kernel/syslog messages # tail /var/log/warn # System warnings messages see syslog.conf Users# id # Show the active user id with login and group # last # Show last logins on the system # who # Show who is logged on the system # groupadd admin # Add group "admin" and user colin (Linux/Solaris) # useradd -c "Colin Barschel" -g admin -m colin # userdel colin # Delete user colin (Linux/Solaris) # adduser joe # FreeBSD add user joe (interactive) # rmuser joe # FreeBSD delete user joe (interactive) # pw groupadd admin # Use pw on FreeBSD # pw groupmod admin -m newmember # Add a new member to a group # pw useradd colin -c "Colin Barschel" -g admin -m -s /bin/tcsh # pw userdel colin; pw groupdel adminEncrypted passwords are stored in /etc/shadow for Linux and Solaris and /etc/master.passwd on FreeBSD. If the master.passwd is modified manually (say to delete a password), run # pwd_mkdb -p master.passwd to rebuild the database.To temporarily prevent logins system wide (for all users but root) use nologin. The message in nologin will be displayed. # echo "Sorry no login now" > /etc/nologin # (Linux) # echo "Sorry no login now" > /var/run/nologin # (FreeBSD) LimitsSome application require higher limits on open files and sockets (like a proxy web server, database). The default limits are usually too low.LinuxPer shell/scriptThe shell limits are governed byulimit. The status is checked
with ulimit -a. For example to change the open files limit from
1024 to 10240 do:
# ulimit -n 10240 # This is only valid within the shell
The ulimit command can be used in a script to change the limits for the script only.
Per user/processLogin users and applications can be configured in/etc/security/limits.conf. For example:
# cat /etc/security/limits.conf System wideKernel limits are set with sysctl. Permanent limits are set in/etc/sysctl.conf.
# sysctl -a # View all system limits # sysctl fs.file-max # View max open files limit # sysctl fs.file-max=102400 # Change max open files limit # cat /etc/sysctl.conf fs.file-max=102400 # Permanent entry in sysctl.conf # cat /proc/sys/fs/file-nr # How many file descriptors are in use FreeBSDPer shell/scriptUse the commandlimits in csh or tcsh or as in Linux, use ulimit in an sh or bash shell.
Per user/processThe default limits on login are set in/etc/login.conf. An unlimited value is still limited by the system maximal value.
System wideKernel limits are also set with sysctl. Permanent limits are set in/etc/sysctl.conf or /boot/loader.conf. The syntax is the same as Linux but the keys are different.
# sysctl -a # View all system limits # sysctl kern.maxfiles=XXXX # maximum number of file descriptors kern.ipc.nmbclusters=32768 # Permanent entry in /etc/sysctl.conf kern.maxfiles=65536 # Typical values for Squid kern.maxfilesperproc=32768 kern.ipc.somaxconn=8192 # TCP queue. Better for apache/sendmail # sysctl kern.openfiles # How many file descriptors are in use # sysctl kern.ipc.numopensockets # How many open sockets are in useSee The FreeBSD handbook Chapter 11http://www.freebsd.org/handbook/configtuning-kernel-limits.html for details. SolarisThe following values in/etc/system will increase the maximum file descriptors per proc:
set rlim_fd_max = 4096 # Hard limit on file descriptors for a single proc set rlim_fd_cur = 1024 # Soft limit on file descriptors for a single proc RunlevelsLinuxOnce booted, the kernel startsinit which then starts rc which starts all scripts belonging to a runlevel. The scripts are stored in /etc/init.d and are linked into /etc/rc.d/rcN.d with N the runlevel number.The default runlevel is configured in /etc/inittab. It is usually 3 or 5: # grep default: /etc/inittab id:3:initdefault:The actual runlevel (the list is shown below) can be changed with init. For example to go from 3 to 5:
# init 5 # Enters runlevel 5
chkconfig to configure the programs that will be started at boot in a runlevel.
# chkconfig --list # List all init scripts # chkconfig --list sshd # Report the status of sshd # chkconfig sshd --level 35 on # Configure sshd for levels 3 and 5 # chkconfig sshd off # Disable sshd for all runlevelsDebian and Debian based distributions like Ubuntu or Knoppix use the command update-rc.d to manage the runlevels scripts. Default is to start in 2,3,4 and 5 and shutdown in 0,1 and 6.
# update-rc.d sshd defaults # Activate sshd with the default runlevels # update-rc.d sshd start 20 2 3 4 5 . stop 20 0 1 6 . # With explicit arguments # update-rc.d -f sshd remove # Disable sshd for all runlevels # shutdown -h now (or # poweroff) # Shutdown and halt the system FreeBSDThe BSD boot approach is different from the SysV, there are no runlevels. The final boot state (single user, with or without X) is configured in/etc/ttys. All OS scripts are located in /etc/rc.d/ and in /usr/local/etc/rc.d/ for third-party applications. The activation of the service is configured in /etc/rc.conf and /etc/rc.conf.local. The default behavior is configured in /etc/defaults/rc.conf. The scripts responds at least to start|stop|status.
# /etc/rc.d/sshd statusThe process init can also be used to reach one of the following states level. For example # init 6 for reboot.
Reset root passwordLinux method 1At the boot loader (lilo or grub), enter the following boot option:init=/bin/shThe kernel will mount the root partition and init will start the bourne shell
instead of rc and then a runlevel. Use the command passwd at the prompt to change the password and then reboot. Forget the single user mode as you need the password for that.If, after booting, the root partition is mounted read only, remount it rw: # mount -o remount,rw / FreeBSD and Linux method 2FreeBSD won't let you go away with the simple init trick. The solution is to mount the root partition from an other OS (like a rescue CD) and change the password on the disk.
# mount -o rw /dev/ad4s3a /mntAlternatively on FreeBSD, boot in single user mode, remount / rw and use passwd.
# mount -u /; mount -a # will mount / rw
# passwd
# reboot
Kernel modulesLinux# lsmod # List all modules loaded in the kernel # modprobe isdn # To load a module (here isdn) FreeBSD# kldstat # List all modules loaded in the kernel # kldload crypto # To load a module (here crypto) Compile KernelLinux# cd /usr/src/linux FreeBSDTo modify and rebuild the kernel, copy the generic configuration file to a new name and edit it as needed. It is however also possible to edit the fileGENERIC directly.
# cd /usr/src/sys/i386/conf/ # cp GENERIC MYKERNEL # cd /usr/src # make buildkernel KERNCONF=MYKERNEL # make installkernel KERNCONF=MYKERNELTo rebuild the full OS: # make buildworld # Build the full OS but not the kernel # make buildkernel # Use KERNCONF as above if appropriate # make installkernel # reboot # mergemaster -p # Compares only files known to be essential # make installworld # mergemaster # Update all configuration and other files # rebootFor small changes in the source, sometimes the short version is enough:
# make kernel world # Compile and install both kernel and OS
# mergemaster
# reboot
ProcessesListing | Priority | Background/Foreground | Top | Kill Listing and PIDsEach process has a unique number, the PID. A list of all running process is retrieved withps.
# ps -auxefw # Extensive list of all running process
However more typical usage is with a pipe or with pgrep:
# ps axww | grep cron PriorityChange the priority of a running process withrenice. Negative numbers have a higher priority, the lowest is -20 and "nice" have a positive value.
# renice -5 586 # Stronger priority
586: old priority 0, new priority -5
Start the process with a defined priority with nice. Positive is "nice" or weak, negative is strong scheduling priority. Make sure you know if /usr/bin/nice or the shell built-in is used (check with # which nice).
# nice -n -5 top # Stronger priority (/usr/bin/nice) # nice -n 5 top # Weaker priority (/usr/bin/nice) # nice +5 top # tcsh builtin nice (same as above!) Background/ForegroundWhen started from a shell, processes can be brought in the background and back to the foreground with [Ctrl]-[Z] (^Z),bg and fg. For example start two processes, bring them in the background, list the processes with jobs and bring one in the foreground.
# ping cb.vu > ping.logUse nohup to start a process which has to keep running when the shell is closed (immune to hangups).
# nohup ping -i 60 > ping.log & TopThe programtop displays running information of processes.
# topWhile top is running press the key h for a help overview. Useful keys are:
Signals/KillTerminate or send a signal withkill or killall.
# ping -i 60 cb.vu > ping.log &Important signals are:
File SystemDisk info | Boot | Disk usage | Opened files | Mount/remount | Mount SMB | Mount image | Burn ISO | Create image | Memory disk | Disk performance PermissionsChange permission and ownership withchmod and chown. The default umask can be changed for all users in /etc/profile for Linux or /etc/login.conf for FreeBSD. The default umask is usually 022. The umsak is subtracted from 777, thus umask 022 results in a permission 0f 755.
1 --x execute # Mode 764 = exec/read/write | read/write | read 2 -w- write # For: |-- Owner --| |- Group-| |Oth| 4 r-- read ugo=a u=user, g=group, o=others, a=everyone # chmod [OPTION] MODE[,MODE] FILE # MODE is of the form [ugoa]*([-+=]([rwxXst])) # chmod 640 /var/log/maillog # Restrict the log -rw-r----- # chmod u=rw,g=r,o= /var/log/maillog # Same as above # chmod -R o-r /home/* # Recursive remove other readable for all users # chmod u+s /path/to/prog # Set SUID bit on executable (know what you do!) # find / -perm -u+s -print # Find all programs with the SUID bit # chown user:group /path/to/file # Change the user and group ownership of a file # chgrp group /path/to/file # Change the group ownership of a file Disk information# diskinfo -v /dev/ad2 # information about disk (sector/size) FreeBSD # hdparm -I /dev/sda # information about the IDE/ATA disk (Linux) # fdisk /dev/ad2 # Display and manipulate the partition table # smartctl -a /dev/ad2 # Display the disk SMART info BootFreeBSDTo boot an old kernel if the new kernel doesn't boot, stop the boot at during the count down.# unload # load kernel.old # boot System mount points/Disk usage# mount | column -t # Show mounted file-systems on the system # df # display free disk space and mounted devices # cat /proc/partitions # Show all registered partitions (Linux) Disk usage# du -sh * # Directory sizes as listing # du -csh # Total directory size of the current directory # du -ks * | sort -n -r # Sort everything by size in kilobytes # ls -lSr # Show files, biggest last Who has which files openedThis is useful to find out which file is blocking a partition which has to be unmounted and gives a typical error of:# umount /home/ FreeBSD and most Unixes# fstat -f /home # for a mount point # fstat -p PID # for an application with PID # fstat -u user # for a user nameFind opened log file (or other opened files), say for Xorg:
# ps ax | grep Xorg | awk '{print $1}'
1252
# fstat -p 1252
USER CMD PID FD MOUNT INUM MODE SZ|DV R/W
root Xorg 1252 root / 2 drwxr-xr-x 512 r
root Xorg 1252 text /usr 216016 -rws--x--x 1679848 r
root Xorg 1252 0 /var 212042 -rw-r--r-- 56987 w
The file with inum 212042 is the only file in /var:
# find -x /var -inum 212042 /var/log/Xorg.0.log LinuxFind opened files on a mount point withfuser or lsof:
# fuser -m /home # List processes accessing /home
# lsof /home
COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
tcsh 29029 eedcoba cwd DIR 0,18 12288 1048587 /home/eedcoba (guam:/home)
lsof 29140 eedcoba cwd DIR 0,18 12288 1048587 /home/eedcoba (guam:/home)
About an application:
ps ax | grep Xorg | awk '{print $1}'
3324
# lsof -p 3324
COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME
Xorg 3324 root 0w REG 8,6 56296 12492 /var/log/Xorg.0.log
About a single file:
# lsof /var/log/Xorg.0.log COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME Xorg 3324 root 0w REG 8,6 56296 12492 /var/log/Xorg.0.log Mount/remount a file systemFor example the cdrom. If listed in /etc/fstab:# mount /cdromOr find the device in /dev/ or with dmesg FreeBSD# mount -v -t cd9660 /dev/cd0c /mnt # cdrom # mount_cd9660 /dev/wcd0c /cdrom # other method # mount -v -t msdos /dev/fd0c /mnt # floppyEntry in /etc/fstab: # Device Mountpoint FStype Options Dump Pass# /dev/acd0 /cdrom cd9660 ro,noauto 0 0To let users do it:
# sysctl vfs.usermount=1 # Or insert the line "vfs.usermount=1" in /etc/sysctl.conf
Linux# mount -t auto /dev/cdrom /mnt/cdrom # typical cdrom mount command # mount /dev/hdc -t iso9660 -r /cdrom # typical IDE # mount /dev/sdc0 -t iso9660 -r /cdrom # typical SCSIEntry in /etc/fstab: /dev/cdrom /media/cdrom subfs noauto,fs=cdfss,ro,procuid,nosuid,nodev,exec 0 0 Mount a FreeBSD partition with LinuxFind the partition number containing with fdisk, this is usually the root partition, but it could be an other BSD slice too. If the FreeBSD has many slices, they are the one not listed in the fdisk table, but visible in /dev/sda* or /dev/hda*.# fdisk /dev/sda # Find the FreeBSD partition /dev/sda3 * 5357 7905 20474842+ a5 FreeBSD # mount -t ufs -o ufstype=ufs2,ro /dev/sda3 /mnt /dev/sda10 = /tmp; /dev/sda11 /usr # The other slices RemountRemount a device without unmounting it. Necessary for fsck for example# mount -o remount,ro / # Linux # mount -o ro / # FreeBSDCopy the raw data from a cdrom into an iso image: # dd if=/dev/cd0c of=file.iso Mount an SMB shareSuppose we want to access the SMB share myshare on the computer smbserver, the address as typed on a Windows PC is \\smbserver\myshare\. We mount on /mnt/smbshare. Warning> cifs wants an IP or DNS name, not a Windows name.Linux
# smbclient -U user -I 192.168.16.229 -L //smbshare/ # List the shares
# mount -t smbfs -o username=winuser //smbserver/myshare /mnt/smbshare
# mount -t cifs -o username=winuser,password=winpwd //192.168.16.229/myshare /mnt/share
Additionally with the package mount.cifs it is possible to store the credentials in a file, for example /home/user/.smb:
username=winuser password=winpwdAnd mount as follow: # mount -t cifs -o credentials=/home/user/.smb //192.168.16.229/myshare /mnt/smbshare FreeBSDUse -I to give the IP (or DNS name); smbserver is the Windows name.
# smbutil view -I 192.168.16.229 //winuser@smbserver # List the shares
# mount_smbfs -I 192.168.16.229 //winuser@smbserver/myshare /mnt/smbshare
Mount an imageLinux loop-back# mount -t iso9660 -o loop file.iso /mnt # Mount a CD image # mount -t ext3 -o loop file.img /mnt # Mount an image with ext3 fs FreeBSDWith memory device (do # kldload md.ko if necessary):# mdconfig -a -t vnode -f file.iso -u 0Or with virtual node: # vnconfig /dev/vn0c file.iso; mount -t cd9660 /dev/vn0c /mnt Solaris and FreeBSDwith loop-back file interface or lofi:# lofiadm -a file.iso Create and burn an ISO imageThis will copy the cd or DVD sector for sector. Withoutconv=notrunc, the image will be smaller if there is less content on the cd. See below and the dd examples.
# dd if=/dev/hdc of=/tmp/mycd.iso bs=2048 conv=notruncUse mkisofs to create a CD/DVD image from files in a directory. To overcome the file names restrictions: -r enables the Rock Ridge extensions common to UNIX systems, -J enables Joliet extensions used by Microsoft systems. -L allows ISO9660 filenames to begin with a period. # mkisofs -J -L -r -V TITLE -o imagefile.iso /path/to/dirOn FreeBSD, mkisofs is found in the ports in sysutils/cdrtools. Burn a CD/DVD ISO imageFreeBSDFreeBSD does not enable DMA on ATAPI drives by default. DMA is enabled with the sysctl command and the arguments below, or with /boot/loader.conf with the following entries:hw.ata.ata_dma="1" hw.ata.atapi_dma="1"Use burncd with an ATAPI device (burncd is part of the base system) and cdrecord (in sysutils/cdrtools) with a SCSI drive.
# burncd -f /dev/acd0 data imagefile.iso fixate # For ATAPI drive # cdrecord -scanbus # To find the burner device (like 1,0,0) # cdrecord dev=1,0,0 imagefile.iso LinuxAlso usecdrecord with Linux as described above. Additionally it is possible to use the native ATAPI interface which is found with:
# cdrecord dev=ATAPI -scanbusAnd burn the CD/DVD as above. Convert a Nero .nrg file to .isoNero simply adds a 300Kb header to a normal iso image. This can be trimmed with dd.# dd bs=1k if=imagefile.nrg of=imagefile.iso skip=300 Convert a bin/cue image to .isoThe littlebchunk programhttp://freshmeat.net/projects/bchunk/ can do this. It is in the FreeBSD ports in sysutils/bchunk.
# bchunk imagefile.bin imagefile.cue imagefile.iso Create a file based imageFor example a partition of 1GB using the file /usr/vdisk.img.FreeBSD# dd if=/dev/random of=/usr/vdisk.img bs=1K count=1M Linux# dd if=/dev/zero of=/usr/vdisk.img bs=1024k count=1024 Linux with losetup/dev/zero is much faster than urandom, but less secure for encryption.
# dd if=/dev/urandom of=/usr/vdisk.img bs=1024k count=1024 Create a memory file systemA memory based file system is very fast for heavy IO application. How to create a 64 MB partition mounted on /memdisk:FreeBSD# mount_mfs -o rw -s 64M md /memdisk Linux# mount -t tmpfs -osize=64m tmpfs /memdisk Disk performanceRead and write a 1 GB file on partition ad4s3c (/home)# time dd if=/dev/ad4s3c of=/dev/null bs=1024k count=1000 NetworkRouting | Additional IP | Change MAC | Ports | Firewall | IP Forward | NAT | DNS | DHCP | Traffic | QoS | NIS Debugging (See also Traffic analysis)# mii-diag eth0 # Show the link status (Linux) # ifconfig fxp0 # Check the "media" field on FreeBSD # arp -a # Check the router (or host) ARP entry (all OS) # ping cb.vu # The first thing to try... # traceroute cb.vu # Print the route path to destination # mii-diag -F 100baseTx-FD eth0 # Force 100Mbit Full duplex (Linux) # ifconfig fxp0 media 100baseTX mediaopt full-duplex # Same for FreeBSD # netstat -s # System-wide statistics for each network protocol RoutingPrint routing table# route -n # Linux # netstat -rn # Linux, BSD and UNIX # route print # Windows Add and delete a routeFreeBSD# route add 212.117.0.0/16 192.168.1.1 # route delete 212.117.0.0/16 # route add default 192.168.1.1Add the route permanently in /etc/rc.conf static_routes="myroute" route_myroute="-net 212.117.0.0/16 192.168.1.1" Linux# route add -net 192.168.20.0 netmask 255.255.255.0 gw 192.168.16.254 Windows# Route add 192.168.50.0 mask 255.255.255.0 192.168.51.253 # Route add 0.0.0.0 mask 0.0.0.0 192.168.51.254Use add -p to make the route persistent. Configure additional IP addressesLinux# ifconfig eth0 192.168.50.254 netmask 255.255.255.0 # First IP # ifconfig eth0:0 192.168.51.254 netmask 255.255.255.0 # Second IP FreeBSD# ifconfig fxp0 inet 192.168.50.254/24 # First IP # ifconfig fxp0 alias 192.168.51.254 netmask 255.255.255.0 # Second IPPermanent entries in /etc/rc.conf ifconfig_fxp0="inet 192.168.50.254 netmask 255.255.255.0" ifconfig_fxp0_alias0="192.168.51.254 netmask 255.255.255.0" Change MAC address# ifconfig eth0 hw ether 00:01:02:03:04:05 # Linux # ifconfig fxp0 link 00:01:02:03:04:05 # FreeBSD Ports in useListening open ports:# netstat -an | grep LISTEN FirewallCheck if a firewall is running (typical configuration only):Linux# iptables -L -n -v # For status Open the iptables firewall # iptables -Z # Zero the packet and byte counters in all chains # iptables -F # Flush all chains # iptables -X # Delete all chains # iptables -P INPUT ACCEPT # Open everything # iptables -P FORWARD ACCEPT # iptables -P OUTPUT ACCEPT FreeBSD# ipfw show # For status # ipfw list 65535 # if answer is "65535 deny ip from any to any" the fw is disabled # sysctl net.inet.ip.fw.enable=0 # Disable # sysctl net.inet.ip.fw.enable=1 # Enable IP Forward for routingLinuxCheck and then enable IP forward with:
# cat /proc/sys/net/ipv4/ip_forward # Check IP forward 0=off, 1=on
# echo 1 > /proc/sys/net/ipv4/ip_forward
or edit /etc/sysctl.conf with:
net.ipv4.ip_forward = 1 FreeBSDCheck and enable with:# sysctl net.inet.ip.forwarding # Check IP forward 0=off, 1=on # sysctl net.inet.ip.forwarding=1 # sysctl net.inet.ip.fastforwarding=1 # For dedicated router or firewall Permanent with entry in /etc/rc.conf: gateway_enable="YES" # Set to YES if this host will be a gateway. NAT Network Address TranslationLinux# iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE # to activate NAT # iptables -t nat -A PREROUTING -p tcp -d 78.31.70.238 --dport 20022 -j DNAT \ --to 192.168.16.44:22 # Port forward 20022 to internal IP port ssh # iptables -t nat -A PREROUTING -p tcp -d 78.31.70.238 --dport 993:995 -j DNAT \ --to 192.168.16.254:993:995 # Port forward of range 993-995 # ip route flush cache # iptables -L -t nat # Check NAT statusDelete the port forward with -D instead of -A. FreeBSD# natd -s -m -u -dynamic -f /etc/natd.conf -n fxp0Port forward with: # cat /etc/natd.conf DNSOn Unix the DNS entries are valid for all interfaces and are stored in /etc/resolv.conf. The domain to which the host belongs is also stored in this file. A minimal configuration is:nameserver 78.31.70.238 search sleepyowl.net intern.lab domain sleepyowl.netCheck the system domain name with:
# hostname -d # Same as dnsdomainname
WindowsOn Windows the DNS are configured per interface. To display the configured DNS and to flush the DNS cache use:# ipconfig /? # Display help # ipconfig /all # See all information including DNS # ipconfig /flushdns # Flush the DNS cache Forward queriesDig is you friend to test the DNS settings. For example the public DNS server213.133.105.2 ns.second-ns.de can be used for testing. See from which server the client receives the answer (simplified answer).
# dig sleepyowl.net sleepyowl.net. 600 IN A 78.31.70.238 ;; SERVER: 192.168.51.254#53(192.168.51.254)The router 192.168.51.254 answered and the response is the A entry. Any entry can be queried and the DNS server can be selected with @: # dig MX google.comThe program host is also powerful. # host -t MX cb.vu # Get the mail MX entry # host -t NS -T sun.com # Get the NS record over a TCP connection # host -a sleepyowl.net # Get everything Reverse queriesFind the name belonging to an IP address (in-addr.arpa.). This can be done withdig, host and nslookup:
# dig -x 78.31.70.238 # host 78.31.70.238 # nslookup 78.31.70.238 /etc/hostsSingle hosts can be configured in the file /etc/hosts instead of runningnamed locally to resolve the hostname queries. The format is simple, for example:
78.31.70.238 sleepyowl.net sleepyowlThe priority between hosts and a dns query, that is the name resolution order, can be configured in /etc/nsswitch.conf AND /etc/host.conf. The file also exists on Windows, it is usually in:
C:\WINDOWS\SYSTEM32\DRIVERS\ETC DHCPLinuxSome distributions (SuSE) use dhcpcd as client. The default interface is eth0.# dhcpcd -n eth0 # Trigger a renew # dhcpcd -k eth0 # release and shutdownThe lease with the full information is stored in: /var/lib/dhcpcd/dhcpcd-eth0.info FreeBSDFreeBSD (and Debian) uses dhclient. To configure an interface (for example bge0) run:# dhclient bge0The lease with the full information is stored in: /var/db/dhclient.leases.bge0Use /etc/dhclient.confto prepend options or force different options:
# cat /etc/dhclient.conf
interface "rl0" {
prepend domain-name-servers 127.0.0.1;
default domain-name "sleepyowl.net";
supersede domain-name "sleepyowl.net";
}
WindowsThe dhcp lease can be renewed withipconfig:
# ipconfig /renew # renew all adapters # ipconfig /renew LAN # renew the adapter named "LAN" # ipconfig /release WLAN # release the adapter named "WLAN"Yes it is a good idea to rename you adapter with simple names! Traffic analysisBmonhttp://people.suug.ch/~tgr/bmon/ is a small console bandwidth monitor and can display the flow on different interfaces.Sniff with tcpdump# tcpdump -nl -i bge0 not port ssh and src \(192.168.16.121 or 192.168.16.54\)Additional important options:
Scan with nmapNmaphttp://insecure.org/nmap/ is a port scanner with OS detection, it is usually installed on most distributions and is also available for Windows. If you don't scan your servers, hackers do it for you...# nmap cb.vu # scans all reserved TCP ports on the host # nmap -sP 192.168.16.0/24 # Find out which IP are used and by which host on 0/24 # nmap -sS -sV -O cb.vu # Do a stealth SYN scan with version and OS detection PORT STATE SERVICE VERSION 22/tcp open ssh OpenSSH 3.8.1p1 FreeBSD-20060930 (protocol 2.0) 25/tcp open smtp Sendmail smtpd 8.13.6/8.13.6 80/tcp open http Apache httpd 2.0.59 ((FreeBSD) DAV/2 PHP/4. [...] Running: FreeBSD 5.X Uptime 33.120 days (since Fri Aug 31 11:41:04 2007) Traffic control (QoS)Traffic control manages the queuing, policing, scheduling, and other traffic parameters for a network. The following examples are simple practical uses of the Linux and FreeBSD capabilities to better use the available bandwidth.Limit uploadDSL or cable modems have a long queue to improve the upload throughput. However filling the queue with a fast device (e.g. ethernet) will dramatically decrease the interactivity. It is therefore useful to limit the device upload rate to match the physical capacity of the modem, this should greatly improve the interactivity. Set to about 90% of the modem maximal (cable) speed.LinuxFor a 512 Kbit upload modem.# tc qdisc add dev eth0 root tbf rate 480kbit latency 50ms burst 1540 FreeBSDFreeBSD uses thedummynet traffic shaper which is configured with ipfw. Pipes are used to set limits the bandwidth in units of [K|M]{bit/s|Byte/s}, 0 means unlimited bandwidth. Using the same pipe number will reconfigure it. For example limit the upload bandwidth to 500 Kbit.
# kldload dummynet # load the module if necessary # ipfw pipe 1 config bw 500Kbit/s # create a pipe with limited bandwidth # ipfw add pipe 1 ip from me to any # divert the full upload into the pipe Quality of serviceLinuxPriority queuing withtc to optimize VoIP. See the full example on voip-info.org or www.howtoforge.com. Suppose VoIP uses udp on ports 10000:11024 and device eth0 (could also be ppp0 or so). The following commands define the QoS to three queues and force the VoIP traffic to queue 1 with QoS 0x1e (all bits set). The default traffic flows into queue 3 and QoS Minimize-Delay flows into queue 2.
# tc qdisc add dev eth0 root handle 1: prio priomap 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 0Status and remove with # tc -s qdisc ls dev eth0 # queue status # tc qdisc del dev eth0 root # delete all QoS Calculate port range and maskThe tc filter defines the port range with port and mask which you have to calculate. Find the 2^N ending of the port range, deduce the range and convert to HEX. This is your mask. Example for 10000 -> 11024, the range is 1024.# 2^13 (8192) < 10000 < 2^14 (16384) # ending is 2^14 = 16384 # echo "obase=16;(2^14)-1024" | bc # mask is 0x3C00 FreeBSDThe max link bandwidth is 500Kbit/s and we define 3 queues with priority 100:10:1 for VoIP:ssh:all the rest.# ipfw pipe 1 config bw 500Kbit/sStatus and remove with # ipfw list # rules status # ipfw pipe list # pipe status # ipfw flush # deletes all rules but default NIS DebuggingSome commands which should work on a well configured NIS client:# ypwhich # get the connected NIS server name # domainname # The NIS domain name as configured # ypcat group # should display the group from the NIS server # cd /var/yp && make # Rebuild the yp databaseIs ypbind running? # ps auxww | grep ypbind Linux# cat /etc/yp.conf ypserver servername domain domain.net broadcast SSH SCPPublic key | Fingerprint | SCP | Tunneling Public key authenticationConnect to a host without password using public key authentication. The idea is to append your public key to the authorized_keys2 file on the remote host. For this example let's connect host-client to host-server, the key is generated on the client.
# ssh-keygen -t dsa -N '' # cat ~/.ssh/id_dsa.pub | ssh you@host-server "cat - >> ~/.ssh/authorized_keys2" Using the Windows client from ssh.comThe non commercial version of the ssh.com client can be downloaded the main ftp site: ftp.ssh.com/pub/ssh/. Keys generated by the ssh.com client need to be converted for the OpenSSH server. This can be done with the ssh-keygen command.
Using putty for WindowsPuttyhttp://www.chiark.greenend.org.uk/~sgtatham/putty/download.html is a simple and free ssh client for Windows.
Check fingerprintAt the first login, ssh will ask if the unknown host with the fingerprint has to be stored in the known hosts. To avoid a man-in-the-middle attack the administrator of the server can send you the server fingerprint which is then compared on the first login. Usessh-keygen -l to get the fingerprint (on the server):
# ssh-keygen -l -f /etc/ssh/ssh_host_rsa_key.pub # For RSA key 2048 61:33:be:9b:ae:6c:36:31:fd:83:98:b7:99:2d:9f:cd /etc/ssh/ssh_host_rsa_key.pub # ssh-keygen -l -f /etc/ssh/ssh_host_dsa_key.pub # For DSA key (default) 2048 14:4a:aa:d9:73:25:46:6d:0a:48:35:c7:f4:16:d4:ee /etc/ssh/ssh_host_dsa_key.pubNow the client connecting to this server can verify that he is connecting to the right server: # ssh linda The authenticity of host 'linda (192.168.16.54)' can't be established. DSA key fingerprint is 14:4a:aa:d9:73:25:46:6d:0a:48:35:c7:f4:16:d4:ee. Are you sure you want to continue connecting (yes/no)? yes Secure file transferSome simple commands:# scp file.txt host-two:/tmp # scp joe@host-two:/www/*.html /www/tmp # scp -r joe@host-two:/www /www/tmpIn Konqueror or Midnight Commander it is possible to access a remote file system with the address fish://user@gate. However the implementation is very slow. Furthermore it is possible to mount a remote folder with sshfs a file system client based on SCP. See fuse sshfshttp://fuse.sourceforge.net/sshfs.html. TunnelingSSH tunneling allows to forward or reverse forward a port over the SSH connection, thus securing the traffic and accessing ports which would otherwise be blocked. This only works with TCP. The general nomenclature for forward and reverse is (see also ssh and NAT example):# ssh -L localport:desthost:destport user@gate # desthost as seen from the gate # ssh -R destport:desthost:localport user@gate # forwards your localport to destination # ssh -X user@gate # To force X forwardingThis will connect to gate and forward the local port to the host desthost:destport. Note desthost is the destination host as seen by the gate, so if the connection is to the gate, then desthost is localhost. More than one port forward is possible. Direct forward on the gateLet say we want to access the CVS (port 2401) and http (port 80) which are running on the gate. This is the simplest example, desthost is thus localhost, and we use the port 8080 locally instead of 80 so we don't need to be root. Once the ssh session is open, both services are accessible on the local ports.# ssh -L 2401:localhost:2401 -L 8080:localhost:80 user@gate Netbios and remote desktop forward to a second serverLet say a Windows smb server is behind the gate and is not running ssh. We need access to the smb share and also remote desktop to the server.# ssh -L 139:smbserver:139 -L 3388:smbserver:3389 user@gateThe smb share can now be accessed with \\127.0.0.1\, but only if the local share is disabled, because the local share is listening on port 139. It is possible to keep the local share enabled, for this we need to create a new virtual device with a new IP address for the tunnel, the smb share will be connected over this address. Furthermore the local RDP is already listening on 3389, so we choose 3388. For this example let's use a virtual IP of 10.1.1.1.
DebugIf it is not working:
Connect two clients behind NATSuppose two clients are behind a NAT gateway and client cliadmin has to connect to client cliuser (the destination), both can login to the gate with ssh and are running Linux with sshd. You don't need root access anywhere as long as the ports on gate are above 1024. We use 2022 on gate. Also since the gate is used locally, the option GatewayPorts is not necessary.On client cliuser (from destination to gate):
# ssh -R 2022:localhost:22 user@gate # forwards client 22 to gate:2022
On client cliadmin (from host to gate):
# ssh -L 3022:localhost:2022 admin@gate # forwards client 3022 to gate:2022
Now the admin can connect directly to the client cliuser with:
# ssh -p 3022 admin@localhost # local:3022 -> gate:2022 -> client:22
Connect to VNC behind NATSuppose a Windows client with VNC listening on port 5900 has to be accessed from behind NAT. On client cliwin to gate:# ssh -R 15900:localhost:5900 user@gateOn client cliadmin (from host to gate): # ssh -L 5900:localhost:15900 admin@gateNow the admin can connect directly to the client VNC with: # vncconnect -display :0 localhost VPN with SSHAs of version 4.3, OpenSSH can use the tun/tap device to encrypt a tunnel. This is very similar to other TLS based VPN solutions like OpenVPN. One advantage with SSH is that there is no need to install and configure additional software. Additionally the tunnel uses the SSH authentication like pre shared keys. The drawback is that the encapsulation is done over TCP which might result in poor performance on a slow link. Also the tunnel is relying on a single (fragile) TCP connection. This technique is very useful for a quick IP based VPN setup. There is no limitation as with the single TCP port forward, all layer 3/4 protocols like ICMP, TCP/UDP, etc. are forwarded over the VPN. In any case, the following options are needed in the sshd_conf file:PermitRootLogin yes PermitTunnel yes Single P2P connectionHere we are connecting two hosts, hclient and hserver with a peer to peer tunnel. The connection is started from hclient to hserver and is done as root. The tunnel end points are 10.0.1.1 (server) and 10.0.1.2 (client) and we create a device tun5 (this could also be an other number). The procedure is very simple:
Connect to the serverConnection started on the client and commands are executed on the server.Server is on Linuxcli># ssh -w5:5 root@hserver Server is on FreeBSDcli># ssh -w5:5 root@hserver Configure the clientCommands executed on the client:cli># ifconfig tun5 10.0.1.2 netmask 255.255.255.252 # Client is on Linux cli># ifconfig tun5 10.0.1.2 10.0.1.1 # Client is on FreeBSDThe two hosts are now connected and can transparently communicate with any layer 3/4 protocol using the tunnel IP addresses. Connect two networksIn addition to the p2p setup above, it is more useful to connect two private networks with an SSH VPN using two gates. Suppose for the example, netA is 192.168.51.0/24 and netB 192.168.16.0/24. The procedure is similar as above, we only need to add the routing. NAT must be activated on the private interface only if the gates are not the same as the default gateway of their network.192.168.51.0/24 (netA)|gateA <-> gateB|192.168.16.0/24 (netB)
Connect from gateA to gateBConnection is started from gateA and commands are executed on gateB.gateB is on LinuxgateA># ssh -w5:5 root@gateB gateB is on FreeBSDgateA># ssh -w5:5 root@gateB # Creates the tun5 devices gateB># ifconfig tun5 10.0.1.1 10.0.1.2 # Executed on the gateB shell gateB># route add 192.168.51.0/24 10.0.1.2 Configure gateACommands executed on gateA:gateA is on LinuxgateA># ifconfig tun5 10.0.1.2 netmask 255.255.255.252 gateA># route add -net 192.168.16.0 netmask 255.255.255.0 dev tun5 gateA># echo 1 > /proc/sys/net/ipv4/ip_forward gateA># iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE gateA is on FreeBSDgateA># ifconfig tun5 10.0.1.2 10.0.1.1The two private networks are now transparently connected via the SSH VPN. The IP forward and NAT settings are only necessary if the gates are not the default gateways. In this case the clients would not know where to forward the response, and nat must be activated. RSYNCRsync can almost completely replace cp and scp, furthermore interrupted transfers are efficiently restarted. A trailing slash (and the absence thereof) has different meanings, the man page is good... Here some examples:Copy the directories with full content: # rsync -a /home/colin/ /backup/colin/Same as before but over the network and with compression. Rsync uses SSH for the transport per default and will use the ssh key if they are set. Use ":" as with SCP. A typical remote copy: # rsync -axSRzv /home/user/ user@server:/backup/user/Exclude any directory tmp within /home/user/ and keep the relative folders hierarchy, that is the remote directory will have the structure /backup/home/user/. This is typically used for backups. # rsync -azR --exclude /tmp/ /home/user/ user@server:/backup/Use port 20022 for the ssh connection: # rsync -az -e 'ssh -p 20022' /home/colin/ user@server:/backup/colin/Using the rsync daemon (used with "::") is much faster, but not encrypted over ssh. The location of /backup is defined by the configuration in /etc/rsyncd.conf. The variable RSYNC_PASSWORD can be set to avoid the need to enter the password manually. # rsync -axSRz /home/ ruser@hostname::rmodule/backup/Some important options:
Rsync on WindowsRsync is available for Windows through cygwin or as stand-alone packaged in cwrsynchttp://sourceforge.net/projects/sereds. This is very convenient for automated backups. Install one of them (not both) and add the path to the Windows system variables: # Control Panel -> System -> tab Advanced, button Environment Variables. Edit the "Path" system variable and add the full path to the installed rsync, e.g. C:\Program Files\cwRsync\bin or C:\cygwin\bin. This way the commandsrsync and ssh are available in a Windows command shell.
Public key authenticationRsync is automatically tunneled over SSH and thus uses the SSH authentication on the server. Automatic backups have to avoid a user interaction, for this the SSH public key authentication can be used and the rsync command will run without a password.All the following commands are executed within a Windows console. In a console (Start -> Run -> cmd) create and upload the key as described in SSH, change "user" and "server" as appropriate. If the file authorized_keys2 does not exist yet, simply copy id_dsa.pub to authorized_keys2 and upload it. # ssh-keygen -t dsa -N '' # Creates a public and a private key # rsync user@server:.ssh/authorized_keys2 . # Copy the file locally from the server # cat id_dsa.pub >> authorized_keys2 # Or use an editor to add the key # rsync authorized_keys2 user@server:.ssh/ # Copy the file back to the server # del authorized_keys2 # Remove the local copyNow test it with (in one line): rsync -rv "/cygdrive/c/Documents and Settings/%USERNAME%/My Documents/" \ 'user@server:My\ Documents/' Automatic backupUse a batch file to automate the backup and add the file in the scheduled tasks (Programs -> Accessories -> System Tools -> Scheduled Tasks). For example create the file backup.bat and replace user@server.@ECHO OFF REM rsync the directory My Documents SETLOCAL SET CWRSYNCHOME=C:\PROGRAM FILES\CWRSYNC SET CYGWIN=nontsec SET CWOLDPATH=%PATH% REM uncomment the next line when using cygwin SET PATH=%CWRSYNCHOME%\BIN;%PATH% echo Press Control-C to abort rsync -av "/cygdrive/c/Documents and Settings/%USERNAME%/My Documents/" \ 'user@server:My\ Documents/' pause SUDOSudo is a standard way to give users some administrative rights without giving out the root password. Sudo is very useful in a multi user environment with a mix of server and workstations. Simply call the command with sudo:# sudo /etc/init.d/dhcpd restart # Run the rc script as root # sudo -u sysadmin whoami # Run cmd as an other user ConfigurationSudo is configured in/etc/sudoers and must only be edited with visudo. The basic syntax is (the lists are comma separated):
user hosts = (runas) commands # In /etc/sudoers
# cat /etc/sudoers # The actual rules root,ADMINS ALL = (ALL) NOPASSWD: ALL # ADMINS can do anything w/o a password. DEVEL DESKTOP = (ALL) NOPASSWD: ALL # Developers have full right on desktops DEVEL DMZ = (ALL) NOPASSWD: DEBUG # Developers can debug the DMZ servers. # User sysadmin can mess around in the DMZ servers with some commands. sysadmin DMZ = (ALL) NOPASSWD: SYSTEM,PW,DEBUG sysadmin ALL,!DMZ = (ALL) NOPASSWD: ALL # Can do anything outside the DMZ. %dba ALL = (DBA) ALL # Group dba can run as database user. # anyone can mount/unmount a cd-rom on the desktop machines ALL DESKTOP = NOPASSWD: /sbin/mount /cdrom,/sbin/umount /cdrom Encrypt FilesA single fileEncrypt and decrypt:# openssl des -salt -in file -out file.des # openssl des -d -salt -in file.des -out fileNote that the file can of course be a tar archive. tar and encrypt a whole directory# tar -cf - directory | openssl des -salt -out directory.tar.des # Encrypt # openssl des -d -salt -in directory.tar.des | tar -x # Decrypt tar zip and encrypt a whole directory# tar -zcf - directory | openssl des -salt -out directory.tar.gz.des # Encrypt # openssl des -d -salt -in directory.tar.gz.des | tar -xz # Decrypt
Encrypt PartitionsLinux with LUKS | Linux dm-crypt only | FreeBSD GELI | FBSD pwd only There are (many) other alternative methods to encrypt disks, I only show here the methods I know and use. Keep in mind that the security is only good as long the OS has not been tempered with. An intruder could easily record the password from the keyboard events. Furthermore the data is freely accessible when the partition is attached and will not prevent an intruder to have access to it in this state.LinuxThose instructions use the Linuxdm-crypt (device-mapper) facility available on the 2.6 kernel. In this example, lets encrypt the partition /dev/sdc1, it could be however any other partition or disk, or USB or a file based partition created with losetup. In this case we would use /dev/loop0. See file image partition. The device mapper uses labels to identify a partition. We use sdc1 in this example, but it could be any string.
dm-crypt with LUKSLUKS with dm-crypt has better encryption and makes it possible to have multiple passphrase for the same partition or to change the password easily. To test if LUKS is available, simply type# cryptsetup --help, if nothing about LUKS shows up, use the instructions below Without LUKS. First create a partition if necessary: fdisk /dev/sdc.
Create encrypted partition# dd if=/dev/urandom of=/dev/sdc1 # Optional. For paranoids only (takes days) # cryptsetup -y luksFormat /dev/sdc1 # This destroys any data on sdc1 # cryptsetup luksOpen /dev/sdc1 sdc1 # mkfs.ext3 /dev/mapper/sdc1 # create ext3 file system # mount -t ext3 /dev/mapper/sdc1 /mnt # umount /mnt # cryptsetup luksClose sdc1 # Detach the encrypted partition Attach# cryptsetup luksOpen /dev/sdc1 sdc1 # mount -t ext3 /dev/mapper/sdc1 /mnt Detach# umount /mnt # cryptsetup luksClose sdc1 dm-crypt without LUKS# cryptsetup -y create sdc1 /dev/sdc1 # or any other partition like /dev/loop0 # dmsetup ls # check it, will display: sdc1 (254, 0) # mkfs.ext3 /dev/mapper/sdc1 # This is done only the first time! # mount -t ext3 /dev/mapper/sdc1 /mnt # umount /mnt/ # cryptsetup remove sdc1 # Detach the encrypted partitionDo exactly the same (without the mkfs part!) to re-attach the partition. If the password is not correct, the mount command will fail. In this case simply remove the map sdc1 ( cryptsetup remove sdc1) and create it again.
FreeBSDThe two popular FreeBSD disk encryption modules aregbde and geli. I now use geli because it is faster and also uses the crypto device for hardware acceleration. See The FreeBSD handbook Chapter 18.6http://www.freebsd.org/handbook/disks-encrypting.html for all the details. The geli module must be loaded or compiled into the kernel:
options GEOM_ELI Use password and keyI use those settings for a typical disk encryption, it uses a passphrase AND a key to encrypt the master key. That is you need both the password and the generated key/root/ad1.key to attach the partition. The master key is stored inside the partition and is not visible. See below for typical USB or file based image.
Create encrypted partition# dd if=/dev/random of=/root/ad1.key bs=64 count=1 # this key encrypts the mater key # geli init -s 4096 -K /root/ad1.key /dev/ad1 # -s 8192 is also OK for disks # geli attach -k /root/ad1.key /dev/ad1 # DO make a backup of /root/ad1.key # dd if=/dev/random of=/dev/ad1.eli bs=1m # Optional and takes a long time # newfs /dev/ad1.eli # Create file system # mount /dev/ad1.eli /mnt Attach# geli attach -k /root/ad1.key /dev/ad1 DetachThe detach procedure is done automatically on shutdown.# umount /mnt # geli detach /dev/ad1.eli /etc/fstabThe encrypted partition can be configured to be mounted with /etc/fstab. The password will be prompted when booting. The following settings are required for this example:# grep geli /etc/rc.conf geli_devices="ad1" geli_ad1_flags="-k /root/ad1.key" # grep geli /etc/fstab /dev/ad1.eli /home/private ufs rw 0 0 Use password onlyIt is more convenient to encrypt a USB stick or file based image with a passphrase only and no key. In this case it is not necessary to carry the additional key file around. The procedure is very much the same as above, simply without the key file. Let's encrypt a file based image/cryptedfile of 1 GB.
# dd if=/dev/zero of=/cryptedfile bs=1M count=1000 # 1 GB file # mdconfig -at vnode -f /cryptedfile # geli init /dev/md0 # encrypts with password only # geli attach /dev/md0 # newfs -U -m 0 /dev/md0.eli # mount /dev/md0.eli /mnt # umount /dev/md0.eli # geli detach md0.eliIt is now possible to mount this image on an other system with the password only. # mdconfig -at vnode -f /cryptedfile # geli attach /dev/md0 # mount /dev/md0.eli /mnt SSL CertificatesSo called SSL/TLS certificates are cryptographic public key certificates and are composed of a public and a private key. The certificates are used to authenticate the endpoints and encrypt the data. They are used for example on a web server (https) or mail server (imaps).Procedure
Configure OpenSSLWe use /usr/local/certs as directory for this example check or edit /etc/ssl/openssl.cnf accordingly to your settings so you know where the files will be created. Here are the relevant part of openssl.cnf:[ CA_default ]Make sure the directories exist or create them # mkdir -p /usr/local/certs/CA Create a certificate authorityIf you do not have a certificate authority from a vendor, you'll have to create your own. This step is not necessary if one intend to use a vendor to sign the request. To make a certificate authority (CA):# openssl req -new -x509 -days 730 -config /etc/ssl/openssl.cnf \ -keyout CA/private/cakey.pem -out CA/cacert.pem Create a certificate signing requestTo make a new certificate (for mail server or web server for example), first create a request certificate with its private key. If your application do not support encrypted private key (for example UW-IMAP does not), then disable encryption with-nodes.
# openssl req -new -keyout newkey.pem -out newreq.pem \ Sign the certificateThe certificate request has to be signed by the CA to be valid, this step is usually done by the vendor. Note: replace "servername" with the name of your server in the next commands.# cat newreq.pem newkey.pem > new.pem # openssl ca -policy policy_anything -out servernamecert.pem \ -config /etc/ssl/openssl.cnf -infiles new.pem # mv newkey.pem servernamekey.pemNow servernamekey.pem is the private key and servernamecert.pem is the server certificate. Create united certificateThe IMAP server wants to have both private key and server certificate in the same file. And in general, this is also easier to handle, but the file has to be kept securely!. Apache also can deal with it well. Create a file servername.pem containing both the certificate and key.
-----BEGIN RSA PRIVATE KEY----- MIICXQIBAAKBgQDutWy+o/XZ/[...]qK5LqQgT3c9dU6fcR+WuSs6aejdEDDqBRQ -----END RSA PRIVATE KEY----- -----BEGIN CERTIFICATE----- MIIERzCCA7CgAwIBAgIBBDANB[...]iG9w0BAQQFADCBxTELMAkGA1UEBhMCREUx -----END CERTIFICATE-----What we have now in the directory /usr/local/certs/:
View certificate informationTo view the certificate information simply do:# openssl x509 -text -in servernamecert.pem # View the certificate info # openssl req -noout -text -in server.csr # View the request info CVSServer setup | CVS test | SSH tunneling | CVS usage Server setupInitiate the CVSDecide where the main repository will rest and create a root cvs. For example /usr/local/cvs (as root):# mkdir -p /usr/local/cvsAdd a readers file if you want to differentiate read and write permissions Note: Do not (ever) edit files directly into the main cvs, but rather checkout the file, modify it and check it in. We did this with the file writers to define the write access. There are three popular ways to access the CVS at this point. The first two don't need any further configuration. See the examples on CVSROOT below for how to use them:
Network setup with inetdThe CVS can be run locally only if a network access is not needed. For a remote access, the daemon inetd can start the pserver with the following line in /etc/inetd.conf (/etc/xinetd.d/cvs on SuSE):cvspserver stream tcp nowait cvs /usr/bin/cvs cvs \ --allow-root=/usr/local/cvs pserverIt is a good idea to block the cvs port from the Internet with the firewall and use an ssh tunnel to access the repository remotely. Separate authenticationIt is possible to have cvs users which are not part of the OS (no local users). This is actually probably wanted too from the security point of view. Simply add a file named passwd (in the CVSROOT directory) containing the users login and password in the crypt format. This is can be done with the apache htpasswd tool.Note: This passwd file is the only file which has to be edited directly in the CVSROOT directory. Also it won't be checked out. More info with htpasswd --help
# htpasswd -cb passwd user1 password1 # -c creates the file
# htpasswd -b passwd user2 password2
Now add :cvs at the end of each line to tell the cvs server to change the user to cvs (or whatever your cvs server is running under). It looks like this:
# cat passwd user1:xsFjhU22u8Fuo:cvs user2:vnefJOsnnvToM:cvs Test itTest the login as normal user (for example here me)# cvs -d :pserver:colin@192.168.50.254:/usr/local/cvs login Logging in to :pserver:colin@192.168.50.254:2401/usr/local/cvs CVS password: CVSROOT variableThis is an environment variable used to specify the location of the repository we're doing operations on. For local use, it can be just set to the directory of the repository. For use over the network, the transport protocol must be specified. Set the CVSROOT variable withsetenv CVSROOT string on a csh, tcsh shell, or with export CVSROOT=string on a sh, bash shell.
# setenv CVSROOT :pserver:<username>@<host>:/cvsdirectoryWhen the login succeeded one can import a new project into the repository: cd into your project root directory cvs import <module name> <vendor tag> <initial tag> cvs -d :pserver:colin@192.168.50.254:/usr/local/cvs import MyProject MyCompany STARTWhere MyProject is the name of the new project in the repository (used later to checkout). Cvs will import the current directory content into the new project. To checkout: # cvs -d :pserver:colin@192.168.50.254:/usr/local/cvs checkout MyProject SSH tunneling for CVSWe need 2 shells for this. On the first shell we connect to the cvs server with ssh and port-forward the cvs connection. On the second shell we use the cvs normally as if it where running locally.on shell 1: # ssh -L2401:localhost:2401 colin@cvs_server # Connect directly to the CVS server. Or: # ssh -L2401:cvs_server:2401 colin@gateway # Use a gateway to reach the CVSon shell 2: # setenv CVSROOT :pserver:colin@localhost:/usr/local/cvs # cvs login Logging in to :pserver:colin@localhost:2401/usr/local/cvs CVS password: # cvs checkout MyProject/src CVS commands and usageImportThe import command is used to add a whole directory, it must be run from within the directory to be imported. Say the directory /devel/ contains all files and subdirectories to be imported. The directory name on the CVS (the module) will be called "myapp".# cvs import [options] directory-name vendor-tag release-tagAfter a while a new directory "/devel/tools/" was added and it has to be imported too. # cd /devel/tools # cvs import myapp/tools Company R1_0 Checkout update add commit# cvs co myapp/tools # Will only checkout the directory tools # cvs co -r R1_1 myapp # Checkout myapp at release R1_1 (is sticky) # cvs -q -d update -P # A typical CVS update # cvs update -A # Reset any sticky tag (or date, option) # cvs add newfile # Add a new file # cvs add -kb newfile # Add a new binary file # cvs commit file1 file2 # Commit the two files only # cvs commit -m "message" # Commit all changes done with a message Create a patchIt is best to create and apply a patch from the working development directory related to the project, or from within the source directory.# cd /devel/project Apply a patchSometimes it is necessary to strip a directory level from the patch, depending how it was created. In case of difficulties, simply look at the first lines of the patch and try -p0, -p1 or -p2.# cd /devel/project SVNServer setup | SVN+SSH | SVN over http | SVN usage Subversion (SVN)http://subversion.tigris.org/ is a version control system designed to be the successor of CVS (Concurrent Versions System). The concept is similar to CVS, but many shortcomings where improved. See also the SVN bookhttp://svnbook.red-bean.com/en/1.4/.Server setupThe initiation of the repository is fairly simple (here for example/home/svn/ must exist):
# svnadmin create --fs-type fsfs /home/svn/project1Now the access to the repository is made possible with:
# svn import /project1/ file:///home/svn/project1/trunk -m 'Initial import' # svn checkout file:///home/svn/project1The new directory "trunk" is only a convention, this is not required. Remote access with sshNo special setup is required to access the repository via ssh, simply replacefile:// with svn+ssh/hostname. For example:
# svn checkout svn+ssh://hostname/home/svn/project1As with the local file access, every user needs an ssh access to the server (with a local account) and also read/write access. This method might be suitable for a small group. All users could belong to a subversion group which owns the repository, for example: # groupadd subversion # groupmod -A user1 subversion # chown -R root:subversion /home/svn # chmod -R 770 /home/svn Remote access with http (apache)Remote access over http (https) is the only good solution for a larger user group. This method uses the apache authentication, not the local accounts. This is a typical but small apache configuration:LoadModule dav_module modules/mod_dav.so <Location /svn>The apache server needs full access to the repository: # chown -R www:www /home/svnCreate a user with htpasswd2:
# htpasswd -c /etc/svn-passwd user1 # -c creates the file
Access control svn.acl example# Default it read access. "* =" would be default no access [/] * = r [groups] project1-developers = joe, jack, jane # Give write access to the developers [project1:] @project1-developers = rw SVN commands and usageSee also the Subversion Quick Reference Cardhttp://www.cs.put.poznan.pl/csobaniec/Papers/svn-refcard.pdf. Tortoise SVNhttp://tortoisesvn.tigris.org is a nice Windows interface.ImportA new project, that is a directory with some files, is imported into the repository with theimport command. Import is also used to add a directory with its content to an existing project.
# svn help import # Get help for any command # Add a new directory (with content) into the src dir on project1 # svn import /project1/newdir http://host.url/svn/project1/trunk/src -m 'add newdir' Typical SVN commands# svn co http://host.url/svn/project1/trunk # Checkout the most recent version # Tags and branches are created by copying # svn mkdir http://host.url/svn/project1/tags/ # Create the tags directory # svn copy -m "Tag rc1 rel." http://host.url/svn/project1/trunk \ http://host.url/svn/project1/tags/1.0rc1 # svn status [--verbose] # Check files status into working dir # svn add src/file.h src/file.cpp # Add two files # svn commit -m 'Added new class file' # Commit the changes with a message # svn ls http://host.url/svn/project1/tags/ # List all tags # svn move foo.c bar.c # Move (rename) files # svn delete some_old_file # Delete files Useful Commandsless | vi | mail | tar | dd | screen | find | Miscellaneous lessTheless command displays a text document on the console. It is present on most installation.
# less unixtoolbox.xhtmlSome important commands are (^N stands for [control]-[N]):
viVi is present on ANY Linux/Unix installation and it is therefore useful to know some basic commands. There are two modes: command mode and insertion mode. The commands mode is accessed with [ESC], the insertion mode with i.Quit
Search and move
Delete text
mail command is a basic application to read and send email, it is usually installed. To send an email simply type &qu |
