Difference: AccessEOSFiles (r2 vs. r1)

IO with EOS command lines

User can access (list and read) files in CERN EOS from non lxplus nodes, without being authenticated.


-bash-4.2$  export EOS_MGM_URL=root://eosatlas.cern.ch

-bash-4.2$ eos ls -l /eos/atlas/atlasdatadisk/rucio/test.1
-rw-r--r--   2 atlas003 zp             960608 Nov 21  2017 test.1


-bash-4.2$ eos cp /eos/atlas/atlasdatadisk/rucio/test.1 /tmp/file6
[eos-cp] path=/eos/atlas/atlasdatadisk/rucio/test.1 size=960608

[eos-cp] going to copy 1 files and 960.61 kB
[eoscp] test.1                   Total 0.92 MB   |====================| 100.00 % [0.6 MB/s]

[eos-cp] copied 1/1 files and 960.61 kB in 2.75 seconds with 349.58 kB/s

In order to get full permission(write/delete), one should use CERN account to get Kerberos authentication.

In order to write files to EOS, user needs to login to lxplus.cern.ch, EOS uses your uid to authenticate the user, hence authorize user to write to certain directories:

-bash-4.1$ kinit wwu@CERN.CH
Password for wwu@CERN.CH: 
-bash-4.1$ klist 
Ticket cache: FILE:/tmp/krb5cc_256396_pJ3N3w
Default principal: wwu@CERN.CH
Valid starting     Expires            Service principal
02/21/19 11:18:13  02/22/19 12:18:18  krbtgt/CERN.CH@CERN.CH   
renew until 02/28/19 11:18:13



-bash-4.2$  export EOS_MGM_URL=root://eosatlas.cern.ch

-bash-4.2$ eos ls -l /eos/atlas/atlasdatadisk/rucio/test.1
-rw-r--r--   2 atlas003 zp             960608 Nov 21  2017 test.1


-bash-4.2$ eos cp /eos/atlas/atlasdatadisk/rucio/test.1 /tmp/file6
[eos-cp] path=/eos/atlas/atlasdatadisk/rucio/test.1 size=960608

[eos-cp] going to copy 1 files and 960.61 kB
[eoscp] test.1                   Total 0.92 MB   |====================| 100.00 % [0.6 MB/s]

[eos-cp] copied 1/1 files and 960.61 kB in 2.75 seconds with 349.58 kB/s

Direct IO through ROOT

User can also do directly IO to ESO from root, more information can be find here

TFile *file = TFile::Open("root://eosatlas//eos/atlas/atlascerngroupdisk/phys-higgs/HSG1/MxAOD/h012/Archive.h012.SmallFiles_LessThan100Mb/data16/data16_13TeV.periodAll25ns_410ipb_onlyToroidIssues.physics_Main.MxAOD.p2623.h012.root");
xrdcp local.file root://eosuser//eos/user/t/tkouba/dest_file

lxplus FUSE mounted

EOS is fuse-mounted on lxplus.cern.ch, so user can use standard linux file system commands to access the files.

-bash-4.1$ hostname

lxplus013.cern.ch

-bash-4.1$ id
uid=56951(wwu) gid=1307(zp) groups=1307(zp),1097570081 context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023

-bash-4.1$ cp /etc/hosts /eos/user/w/wwu/hosts

-bash-4.1$ ls -l /eos/user/w/wwu/hosts
-rw-r--r--. 1 wwu zp 158 Feb 19 19:39 /eos/user/w/wwu/hosts

-bash-4.1$ cp /eos/user/w/wwu/hosts /tmp/file1

-- WenjingWu - 19 Feb 2019

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