If you are browsing around in a terminal and want to see the contents of a .zip file, unzip is able to just list the contents but not actually extract them:
unzip -l myarchive.zipAlternatively, if you want to open a .zip file in a GUI window to browse it’s contents do this:
file-roller myarchive.zipIt will open up Archive Manager to look at the contents.
I had to copy the contents of a .iso file. It’s easy to mount it and see what’s in the iso.
# mkdir /mnt/iso
# mount -o loop VMware-VMvisor-Installer-5.1.0-799733.x86_64.iso /mnt/iso
# cd /mnt/disk
# ls
a.b00 ata_pata.v05 boot.cfg ima_qla4.v00 isolinux.bin misc_dri.v00 net_e100.v01 net_r816.v00 ohci_usb.v00 sata_sat.v02 scsi_bnx.v00 scsi_meg.v01 scsi_qla.v01 upgrade xlibs.v00
ata_pata.v00 ata_pata.v06 chardevs.b00 imgdb.tgz isolinux.cfg net_be2n.v00 net_enic.v00 net_r816.v01 safeboot.c32 sata_sat.v03 scsi_fni.v00 scsi_meg.v02 scsi_rst.v00 user.b00 xorg.v00
ata_pata.v01 ata_pata.v07 efi imgpayld.tgz k.b00 net_bnx2.v00 net_forc.v00 net_s2io.v00 sata_ahc.v00 sata_sat.v04 scsi_hps.v00 scsi_mpt.v00 s.v00 useropts.gz
ata_pata.v02 b.b00 efiboot.img ipmi_ipm.v00 mboot.c32 net_bnx2.v01 net_igb.v00 net_sky2.v00 sata_ata.v00 scsi_aac.v00 scsi_ips.v00 scsi_mpt.v01 tboot.b00 vmware-esx-base-osl.txt
ata_pata.v03 block_cc.v00 ehci_ehc.v00 ipmi_ipm.v01 menu.c32 net_cnic.v00 net_ixgb.v00 net_tg3.v00 sata_sat.v00 scsi_adp.v00 scsi_lpf.v00 scsi_mpt.v02 tools.t00 vmware-esx-base-readme
ata_pata.v04 boot.cat esx_dvfi.v00 ipmi_ipm.v02 misc_cni.v00 net_e100.v00 net_nx_n.v00 net_vmxn.v00 sata_sat.v01 scsi_aic.v00 scsi_meg.v00 scsi_qla.v00 uhci_usb.v00 weaselin.t00
#
Now the contents of /mnt/disk appear as if you had burned the .iso and put it in the CD drive.
If you want to find all symlinks on a file system or in a folder use this:
find . -type l -lsSometimes it’s necessary to do things with sequences in Bash. If you want to create a bunch of directories that will be mount points for NFS servers you could do this:
# mkdir /mnt/fs42
# mkdir /mnt/fs42/vol0
# mkdir /mnt/fs42/vol1
# mkdir /mnt/fs42/vol2
# mkdir /mnt/fs42/vol3But, even the best experts at the “up arrow key” wouldn’t want to do this for 50 file servers. A nested for loop would work, but it’s not necessarily the easiest way to go. The command seq makes a sequence of integers bounded by the numbers specified.
ok:
for i in `seq 1 50`; do for j in `seq 0 3`; do mkdir -p /mnt/fs$i/vol$j; done; done;
Using Bash sequences, you can tell the shell to interpret this {1..50} as a list of integers between 1 and 50. This also works with letters like {a..t}.
# echo {a..t}
a b c d e f g h i j k l m n o p q r s t
# echo {0..50}
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
way better:
# mkdir -p /mnt/fs{1..50}/vol{0..3}
of course if you have non-sequential lists, you may have to specify each element like this:
{1,3,4,5,6,9}
# sed -i '$d' file.txtAdd a static route on a NetApp appliance:
route add net 10.237.0.0/16 10.121.0.6 1 Remove static route:
route delete 10.237.0.0Add default route:
route add default 10.10.0.1 1Remove default route:
route delete default
By default ssh runs on TCP port 22. If you have a ssh configured to listen on a non standard port, you may need a special option to make rsync connect to that port. I was writing a quick backup script for this worpress site, and ran into this issue. In my case I was trying to rsync to a remote server with ssh listening on 4590. You have to give rsync a special ssh option:
# rsync -a --rsh='ssh -p 4590' /srv/www/wp-uploads/ backupsite.com:/backups/wp/wp-uplodas
To find the 10 newest items in your home directory you can just use ls.
# cd
# ls -lt | head
total 1197116
-rw-r--r-- 1 fordodone fordodone 5353 2013-04-23 10:42 file1
-rw-r--r-- 1 fordodone fordodone 2945 2013-04-23 10:21 file2
drwxr-xr-x 2 fordodone fordodone 12288 2013-04-12 08:53 bin
-rw-r--r-- 1 fordodone fordodone 0 2013-03-27 08:45 file3
-rw------- 1 fordodone fordodone 90420 2013-03-23 09:03 file4
-rw-r--r-- 1 fordodone fordodone 83 2013-03-19 10:35 file5
-rw-r--r-- 1 fordodone fordodone 8683 2013-03-15 10:26 file6
-rw-r--r-- 1 fordodone fordodone 28628 2013-03-15 09:15 file7
-rw-r--r-- 1 fordodone fordodone 81303 2013-03-15 09:15 file8
You could even get more aggressive by throwing the recursive flag in. Simple, right? But what if you need to recurse a large number of files and directories on a storage system, say 123,000 directories and 37 million files. I think find might be the way to go.
This will find files modified in the last 24 hours:
# find . -type f -mtime -1 -lsfind doesn’t really provide granular control of searching for files with a certain modified time. If you just want to find files that have been modified today (i.e. since 12am) we can use the -newer flag. First touch a temporary file with a timestamp to compare to files you want to find. In this case we make a date string of 04240000, or today at 00:00, and touch a file with that timestamp. Then use find to find files that are newer than the timestamp of the file you just touched.
# touch -t `date +%m%d0000` /tmp/compare
# find . -type f -newer /tmp/compare
(long output)
# rm /tmp/compare
When troubleshooting network connectivity issues the best method is to begin with the lower layers of the OSI model and work your way up until you eliminate the problem. It’s similar to the way some people troubleshoot helpdesk issues, where the first question is always “is it plugged in?”
Suppose you have 2 hosts, and you are trying to do an snmp query from one to the other. It doesn’t work.
# snmpwalk -v2c -c public 10.210.0.142 Timeout: No Response from 10.210.0.142
You try pinging one from the other and you get replies. At this point you know that everything is working through layer 3, but something is not right with the transport layer. If you were troubleshooting a TCP based application, you could just use ol’ telnet to test if the port will open up. To see if a webserver is running you could try to telnet to port 80. UDP is a connectionless protocol, and can’t be tested like TCP. Here is where you can use nmap to see if the UDP port in question is open. In this case we know that by default snmpd listens on UDP 161.
# nmap -sU -v -p161 10.210.0.142
Starting Nmap 5.00 ( http://nmap.org ) at 2013-04-24 11:27 MST
NSE: Loaded 0 scripts for scanning.
Initiating ARP Ping Scan at 11:27
Scanning 10.210.0.142 [1 port]
Completed ARP Ping Scan at 11:27, 0.03s elapsed (1 total hosts)
Initiating UDP Scan at 11:27
Scanning example.fordodone.com (10.210.0.142) [1 port]
Completed UDP Scan at 11:27, 0.07s elapsed (1 total ports)
Host example.fordodone.com (10.210.0.142) is up (0.00100s latency).
Interesting ports on example.fordodone.com (10.210.0.142):
PORT STATE SERVICE
161/udp closed snmp
MAC Address: 00:0C:29:A2:BE:4D (VMware)
Read data files from: /usr/share/nmap
Nmap done: 1 IP address (1 host up) scanned in 0.43 seconds
Raw packets sent: 2 (70B) | Rcvd: 2 (98B)
Well, there you go. The port is closed. No wonder our queries were timing out. Remove the -p161 part to just scan for all open UDP ports. Also, if your host doesn’t allow icmp, you can use -P0 to just skip host discovery, and assume it’s up. Depending whether they are open, filtered, or closed, you can start to diagnose what’s going on, i.e. snmpd crashed, firewall is blocking it, etc.
If you need to get the last few characters of a string, you can just use awk. This works great because you don’t have to know how long or short the string is to begin with. It first gets the length of the string. So in this example the length is 9 characters, and the ‘1’ would be in position 9 of the string. Then it subtracts 2 from position 9, to get position 7 (which is the ‘3’), then it gets 3 characters starting from position 7: ‘371’
# echo server371 | awk '{print substr($0,length($0)-2,3)}'
371
# echo anotherserver892 | awk '{print substr($0,length($0)-2,3)}'
892